Aliénor Richard

Angèle Van Hamme

Xavier Drevelle

Jean-Louis Golmard

Sabine Meunier

Marie-Laure L Welter
email: marie-laure.welter@aphp.fr.

M.- L W Drafted

M L W Conception

Contribution of the supplementary motor area and the cerebellum to the anticipatory postural adjustments and execution phases of human gait initiation

Keywords: Figures, 4 Tables, 59 Gait initiation, Anticipatory postural adjustments, Supplementary motor area, Cerebellum, Transcranial magnetic stimulation Disclosures

Several brain structures including the brainstem, the cerebellum and the frontal cortico-basal ganglia network, with the primary and premotor areas have been shown to participate in the functional organisation of gait initiation and postural control in humans, but their respective roles remain poorly understood. The aim of this study was to better understand the role of the supplementary motor area (SMA) and posterior cerebellum in the gait initiation process. Gait initiation parameters were recorded in 22 controls both before and after continuous theta burst transcranial stimulation (cTBS) of the SMA and cerebellum, and were compared to sham stimulation, using a randomized double-blind design study. The two phases of gait initiation process were analysed: anticipatory postural adjustments (APAs) and execution, with recordings of soleus and tibialis anterior muscles. Functional inhibition of the SMA led to a shortened APA phase duration with advanced and increased muscle activity; during execution, it also advanced muscle co-activation and decreased the duration of stance soleus activity. Cerebellar functional inhibition did not influence the APA phase duration and amplitude but increased muscle coactivation, it decreased execution duration and showed a trend to increase velocity, with increased swing soleus muscle duration and activity. The results suggest that the SMA contributes to both the timing and amplitude of the APAs with no influence on step execution and the posterior cerebellum in the coupling between the APAs and execution phases and leg muscle activity pattern during gait initiation.

Highlights

 Using transcranial magnetic stimulation, we investigate the role of the SMA and posterior cerebellum in the gait initiation  SMA contributes to both the timing and amplitude of the APAs  The posterior cerebellum participates to the coupling between the APAs and execution phases  The posterior cerebellum also contributes to intra-and inter-limb muscle activity pattern

Introduction

In humans, gait initiation is particularly challenging for motor and postural control as the subject has to simultaneously perform a whole body forward movement and pass from a stable (double leg stance) to an unstable position (single leg stance). It is associated with anticipatory postural adjustments (APAs) with a backward and lateral shift of the centre of foot pressure (CoP) towards the swing leg, in relation with activation of both tibialis anterior (TA) muscles, allowing the swing leg to lift. The neural substrates for APAs generation and step execution are not fully known. In animals, locomotion can be initiated by electrical or chemical activation of the supplementary motor area at the cortical level, and the subthalamic, the mesencephalic locomotor and cerebellar midline regions at the subcortical level [START_REF] Mori | Site-specific postural and locomotor changes evoked in awake, freely moving intact cats by stimulating the brainstem[END_REF][START_REF] Takakusaki | Role of basal ganglia-brainstem systems in the control of postural muscle tone and locomotion[END_REF]). In humans, few studies have examined the role of these brain regions in the gait initiation process. However, repetitive transcranial magnetic stimulation applied above the SMA provokes a shortening of the APA duration of the first step after stimulation with no change in APA amplitude (Jacobs et al. 2009a). Startle stimuli, thought to modulate pontomesencephalic reticular formation activity, shorten APAs with no change in the step execution characteristics [START_REF] Queralt | Speeding up gait initiation and gaitpattern with a startling stimulus[END_REF]. Acoustic stimuli can also elicit APAs without being followed by step execution [START_REF] Delval | Anticipatory postural adjustments during step initiation: elicitation by auditory stimulation of differing intensities[END_REF]), but only when the subject is expecting to initiate a step, suggesting that the brainstem releases APAs depending on the cognitive context (to walk or not) [START_REF] Mackinnon | Preparation of anticipatory postural adjustments prior to stepping[END_REF]). Lastly, transcranial direct current stimulation applied over the cerebellum affects spatial characteristics of walking during locomotor adaptation [START_REF] Jayaram | Modulating locomotor adaptation with cerebellar stimulation[END_REF]), but the effects of cerebellar stimulation on APAs generation and gait initiation have not been studied. In patients with lesions and/or dysfunction of these different brain regions, various gait initiation deficits have also been reported. In patients with premotor cortical areas involving the SMA, a lack of gait initiation (or freezing of gait-FOG phenomenon) has been reported with an inability to lift the feet from the ground and execute the first step [START_REF] Bartels | Brain imaging in patients with freezing of gait[END_REF][START_REF] Nadeau | Gait apraxia: further clues to localization[END_REF][START_REF] Nutt | Human walking and higher-level gait disorders, particularly in the elderly[END_REF]. Such a FOG phenomenon is also observed in patients with mesencephalic locomotor region (MLR) lesions [START_REF] Masdeu | Astasia and gait failure with damage of the pontomesencephalic locomotor region[END_REF] and people with Parkinson's disease (PD) [START_REF] Giladi | Freezing phenomenon in patients with parkinsonian syndromes[END_REF]) and has been linked to altered APAs prior to gait initiation (Jacobs et al. 2009b) with reduced SMA-MLR connectivity [START_REF] Gallea | Pedunculopontine network dysfunction in Parkinson's disease with postural control and sleep disorders[END_REF][START_REF] Halliday | The initiation of gait in young, elderly, and Parkinson's disease subjects[END_REF][START_REF] Okada | Variable initial swing side and prolonged double limb support represent abnormalities of the first three steps of gait initiation in patients with Parkinson's disease with freezing of gait[END_REF]. Patients with cerebellar lesions or dysfunction show increased stride width and shorter stride length with longer duration and increased lower leg muscle activity and co-activation [START_REF] Timmann | Classically conditioned withdrawal reflex in cerebellar patients. 1. Impaired conditioned responses[END_REF]; with abnormal temporal organisation of the muscular pattern [START_REF] Bruttini | Temporal disruption of upper-limb anticipatory postural adjustments in cerebellar ataxic patients[END_REF][START_REF] Martino | Locomotor patterns in cerebellar ataxia[END_REF].

Recently, distorted APAs prior to step execution and altered postural control during walking with shorter and irregular steps [START_REF] Fernandez | Gait initiation impairments in both Essential Tremor and Parkinson's disease[END_REF][START_REF] Morton | Mechanisms of cerebellar gait ataxia[END_REF] have been reported in patients suffering from essential tremor (ET), these patients presented with posterior cerebellar atrophy [START_REF] Gallea | Intrinsic signature of essential tremor in the cerebello-frontal network[END_REF]. Taken together these data support the involvement of the cortico (SMA)-pontine-cerebellothalamo-cortical pathway in APAs generation and the gait initiation process.

In order to provide a more detailed understanding of how the cortico (SMA)pontine-cerebello-thalamo-cortical pathway contributes to the preparation and the execution of the first step in humans, we selectively disrupted the SMA and the cerebellum with continuous theta burst repetitive transcranial magnetic stimulation (cTBS) and evaluated the effects of the stimulation on the APAs and execution phases of gait initiation. Consistent with previous studies, we hypothesised that the SMA would be mainly involved in generating the APAs to lift the leg from the ground while the cerebellum would adjust the postural balance and foot placement during walking.

Experimental procedures

Participants

Twenty-two healthy volunteers (14M/8F, mean age ± SD = 29.5 ± 7.3 years) were included in this study which received approval from the local ethics committee (Paris VI University) and was promoted by the INSERM (C12-05, N° ID RCB 2012-A00796-37, ClinicalTrials.gov Registration NCT02976298). All the participants gave written informed consent to participate. Exclusion criteria were any history of peripheral neurological or orthopaedic disease, and of central nervous systems or psychotropic drug use or contraindication to rTMS [START_REF] Rossi | Safety, ethical considerations, and application guidelines for the use of transcranial magnetic stimulation in clinical practice and research[END_REF].

Gait initiation protocol

Subjects, barefoot, and standing upright and motionless on a force plate (0.9 x 1.8 m, Advanced Mechanical Technology Inc. LG6-4-1, USA) were instructed to commence walking for 5 m (5-7 steps per trial) following an auditory cue. The outlines of the participants' feet were recorded to ensure that stance width remained consistent throughout the experiments. In each trial, the first two steps were captured for analysis. The subjects were instructed to walk at their usual self-paced speed. Each subject walked a total of 10 trials before and after rTMS. The subjects performed separate sessions in a randomised order for rTMS over the SMA, cerebellum and sham stimulation (to either SMA or cerebellum). The sessions were separated by at least 7 days.

rTMS protocol

The intensity of stimulation applied to SMA or cerebellum was chosen relative to the active motor thresholds (aMT) of the right tibialis anterior (TA) or right abductor pollicis brevis (APB) muscles respectively, as previously reported [START_REF] Gerloff | Stimulation over the human supplementary motor area interferes with the organization of future elements in complex motor sequences[END_REF]) [START_REF] Popa | Cerebellar rTMS stimulation may induce prolonged clinical benefits in essential tremor, and subjacent changes in functional connectivity: an open label trial[END_REF]. The rationale for using TA muscle representation as hotspots for adjusting SMA stimulation intensity was that leg representations in the SMA and the primary motor cortex are located in adjacent positions and at a similar depth in the interhemispheric fissure [START_REF] Gerloff | Stimulation over the human supplementary motor area interferes with the organization of future elements in complex motor sequences[END_REF]. Accordingly stimulation sessions started by identifying the motor 'hot spot' of either the right TA or right APB muscles according to the session and calculating their aMT using standard procedures [START_REF] Rossini | Non-invasive electrical and magnetic stimulation of the brain, spinal cord and roots: basic principles and procedures for routine clinical application. Report of an IFCN committee[END_REF][START_REF] Rothwell | Techniques and mechanisms of action of transcranial stimulation of the human motor cortex[END_REF]). To that end TMS pulses were applied by using a 70-mm figure-of-eight coil connected to a Rapid2 magnetic stimulator (Magstim Company).

Induced currents were biphasic and directed posterior to anterior [START_REF] Arai | Effective connectivity between human supplementary motor area and primary motor cortex: a paired-coil TMS study[END_REF].

For the TA muscle, the coil was held on or close to the midline with the handle pointing backwards. For the APB muscle, the coil was held at ~45° from the midline for optimal trans-synaptic activation of the motor cortex [START_REF] Kaneko | The effect of current direction induced by transcranial magnetic stimulation on the corticospinal excitability in human brain[END_REF][START_REF] Werhahn | The effect of magnetic coil orientation on the latency of surface EMG and single motor unit responses in the first dorsal interosseous muscle[END_REF].

The SMA and cerebellum targets were marked on the individual brain MRIs by the use of an MRI-based neuro-navigation system (eXimia 2.2.0, Nextstim Ltd). For the SMA, the target was the SMA proper and marked on the MRI relative to a vertical line from the anterior commissure perpendicular to the antero-posterior commissure line in the sagittal place, which is a standardized separator for the SMA proper and the pre-SMA [START_REF] Picard | Motor areas of the medial wall: a review of their location and functional activation[END_REF][START_REF] Vorobiev | Parcellation of human mesial area 6: cytoarchitectonic evidence for three separate areas[END_REF][START_REF] Zilles | Anatomy and transmitter receptors of the supplementary motor areas in the human and nonhuman primate brain[END_REF], The centre of the coil was positioned over the target, with the coil handle pointing backwards so that the induced current had a posterior-anterior orientation. For the cerebellum, stimulation was applied consecutively to each side targeting lobule VIII of the cerebellum [START_REF] Popa | Long-lasting inhibition of cerebellar output[END_REF][START_REF] Popa | Cerebellar rTMS stimulation may induce prolonged clinical benefits in essential tremor, and subjacent changes in functional connectivity: an open label trial[END_REF], with the coil handle pointing upwards so that the induced current had a caudal to rostral orientation.

Continuous theta-burst stimulation (cTBS) protocol [START_REF] Huang | Theta burst stimulation of the human motor cortex[END_REF] was used with 600 stimuli delivered at 80% TA aMT (for SMA) or 80% APB aMT (for cerebellum) in three-pulse bursts at 50 Hz, repeated every 200 ms continuously for 40 s (5 Hz).

For sham stimulation (delivered with a cTBS pattern), we used a 'sham' coil that delivered only 10% of the intensity. The stimulation intensities used in this study are well below the maximum limit recommended by current rTMS safety guidelines [START_REF] Rossi | Safety, ethical considerations, and application guidelines for the use of transcranial magnetic stimulation in clinical practice and research[END_REF].

Data collection and analysis

The investigators analysing kinematic, dynamic and EMG data were blinded to the stimulation conditions.

Kinetic and dynamic data

The spatial and temporal kinetics parameters, i.e. acceleration and velocity of the centre of gravity (CoG) and displacements of centre of foot pressure (CoP), were extracted from the force platform data in real time and displayed in a custom-built MATLAB interface [START_REF] Chastan | Influence of sensory inputs and motor demands on the control of the centre of mass velocity during gait initiation in humans[END_REF]. The force platform analogue signals were sampled at 1000 Hz.

The onset of the APAs was defined as the moment of the first biomechanical event (t0) with posterior and lateral CoP displacement (Figure 1), and its end as the moment of the foot-off of the swing leg (FO1). The APAs phase was divided in 2 distinct phases [START_REF] Hass | The influence of Tai Chi training on the center of pressure trajectory during gait initiation in older adults[END_REF]): the S1 phase starting at t0 and ending at the time of the maximum posterior and lateral CoP shift, and the S2 phase starting at the onset of the lateral shift of the CoP in the opposite direction towards the stance limb and ending when the CoP is in its most lateral and posterior position under the stance limb (Figure 1). The APAs duration and maximum posterior and lateral CoP displacements were measured.

The step execution phase was defined as the period between FO1 and the foot-off of the stance leg (FO2). The step length, step width, execution velocity and duration of the swing (time between FO1 and the foot-contact of the stance leg -FC1) and double stance (period between the foot contact of the swing leg -FC1 and FO2) phases were calculated (Figure 1). Two values were extracted from the vertical CoG velocity: the peak negative value during the swing phase (V1) and its value at the time of foot contact (V2), allowing us to calculate the braking index ((V1-V2)/V1*100), which reflects active postural control [START_REF] Welter | Control of vertical components of gait during initiation of walking in normal adults and patients with progressive supranuclear palsy[END_REF].

EMG data

Electromyographic (EMG) activity of the Soleus (SOL) and Tibialis anterior (TA) muscles were recorded with surface bipolar electrodes according to SENIAM procedure [START_REF] Hermens | Development of recommendations for SEMG sensors and sensor placement procedures[END_REF] (WAVE Plus, Ref. WP180, Cometa srl, Italy). The EMG signals were band-pass filtered at 30-300 Hz (6th order Butterworth filter), and rectification and low-pass filtering at 50 Hz (2nd order Butterworth, zero-phase forward and reverse filter) were applied. Muscular bursts were detected by the Teager-Kaiser energy operator method by calculating the energy of the signal [START_REF] Solnik | Teager-Kaiser energy operator signal conditioning improves EMG onset detection[END_REF]. The linear envelopes of each muscular burst were measured, normalised to the maximum peak amplitude in each gait condition and the root mean square (RMS) calculated [START_REF] Barzilay | A fast implementation for EMG signal linear envelope computation[END_REF]. The onset, duration of each SOL and TA muscles burst and co-contraction (simultaneous SOL and TA muscles activity) were calculated. We calculated a ratio of co-contraction by dividing the linear envelope of SOL or TA muscle activity with the sum of the SOL and TA linear envelopes [START_REF] Hesse | Lower limb muscle activity in ambulatory children with cerebral palsy before and after the treatment with Botulinum toxin A[END_REF].

Statistical Analysis

For each stimulation condition, we employed a linear mixed effects model with two fixed effects: stimulation (before stimulation, sham-cTBS and cerebellar-cTBS or SMA-cTBS) and day (chronological order of sessions), adding a random effect on subjects to take into account the inter-subject variability. When a significant main effect was seen, the Tukey-Kramer test was used for multiple comparisons. Statistical analyses were performed using R (version 3.2.2). The significance level was taken as p<0.05 with Bonferroni correction. We considered as significant the changes induced by the cTBS only if there was a significant difference between the values obtained before and after the stimulation and a difference between the values obtained during real and sham cTBS. We considered as a trend the changes induced by cTBS if there was a significant difference between the values obtained before versus after the stimulation or after active cTBS versus sham stimulation, but no difference between the values obtained at baseline and after sham stimulation.

Results

Effects of functional inactivation of the SMA or cerebellum on the APAs phase

With SMA-cTBS, the APAs phase duration significantly decreased, the swing SOL muscle activity started significantly earlier and the stance TA muscle RMS activity significantly increased (Figure 2). In comparison to baseline, after SMA-cTBS, the S2 phase duration tended to decrease and the stance SOL muscle activity to start earlier.

Lastly, with SMA-cTBS in comparison to sham stimulation, the lateral CoP displacement tended to increase and the swing SOL muscle activity tended to be activated longer and with increased RMS amplitude (Table 1).

With cerebellar-cTBS, the amplitude and timing of APAs were not significantly modified, but the duration of the TA and SOL muscle co-activation of the stance leg significantly increased (Table 1). After cerebellar-cTBS, the stance TA muscle activity tended to start later in comparison to baseline, and the duration of the swing and stance SOL muscle activity tended to increase. Lastly, with cerebellar -cTBS the lateral CoP shift tended to decrease in comparison to sham stimulation, (Table 1).

Effect of functional inhibition of the SMA or cerebellum on step execution

With SMA-cTBS, the execution and double-stance durations, step length, execution velocity (Figure 2) and braking index (not shown) were not significantly modified.

The stance SOL muscle activity duration significantly decreased (Table 2). In comparison to baseline, the swing TA muscle activity duration tended to decrease and the swing SOL-TA muscle co-activation to start earlier (Table 2).

With cerebellar-cTBS, the execution duration was significantly lower with no significant change in the double-stance duration, step length, execution velocity (Figure 2) or braking index (not shown). The swing SOL muscle activity duration was significantly increased (Figure 2). With cerebellar-cTBS, the swing SOL muscle activity RMS amplitude tended to increase in comparison to baseline, with reduced swing TA muscle RMS amplitude. Lastly, with cerebellar-cTBS the swing TA muscle activity duration tended to decrease in comparison to sham stimulation (Figure 2, Table 2).

Discussion

In the present study, we investigated how the APAs and step execution could be modified by cTBS over the SMA and the cerebellum in healthy subjects. Shorter APAs were produced by cTBS over the SMA with earlier activation of swing SOL muscle, with no significant changes in the step execution parameters, except for a shorter stance SOL muscle activation. Conversely, no significant change in the APAs timings and amplitudes were induced by cTBS over the cerebellum but an increased stance SOL-TA muscle co-activation duration during APAs and a shorter step execution duration with longer swing SOL muscle activation. Neither SMA nor cerebellar-cTBS provoked significant changes in the step length and velocity or postural control during gait execution (i.e. double stance duration and braking index).

In this study, we used the classical parameters used for cTBS, i.e. 0.8 aMT, 600 pulses, thought to induce a transient decrease in synaptic efficacy in the targeted area lasting approximately 30 minutes after stimulation [START_REF] Huang | Theta burst stimulation of the human motor cortex[END_REF], through a combination of long-term depression and long-term potentiation mechanisms [START_REF] Huang | Theta burst stimulation of the human motor cortex[END_REF][START_REF] Stagg | Neurochemical effects of theta burst stimulation as assessed by magnetic resonance spectroscopy[END_REF], with, however, a significant inter-subject variability. In our study, cTBS of the SMA led probably to a reduction in its output signal that provoked increased APAs performance with changes both in the timing (shortening) and amplitude (tendency to increase CoP displacements) of the APAs, related to an earlier and greater activation of TA muscles [START_REF] Mann | The initiation of gait[END_REF]. Our results are in line with reports of reduced APAs durations prior to step initiation with 1 Hz rTMS of the SMA (Jacobs et al. 2009a). This effect could result from disruption of sensory perception of self-generated actions [START_REF] Haggard | Supplementary motor area provides an efferent signal for sensory suppression[END_REF], in addition to changes in perception threshold [START_REF] Legon | Continuous theta burst stimulation of the supplementary motor area: effect upon perception and somatosensory and motor evoked potentials[END_REF], leading to decreased effort perception [START_REF] Zenon | Disrupting the supplementary motor area makes physical effort appear less effortful[END_REF] with, in consequence, an increased force production and increased muscle activity (our results). Another explanation would be that SMA disruption interferes with the automatic inhibitory control of motor responses [START_REF] Albares | The dorsal medial frontal cortex mediates automatic motor inhibition in uncertain contexts: evidence from combined fMRI and EEG studies[END_REF]. The finding that SMA disruption significantly improves akinesia [START_REF] Eggers | Theta burst stimulation over the supplementary motor area in Parkinson's disease[END_REF] and decreases abnormally prolonged APAs phase durations prior to gait initiation (Jacobs et al. 2009a) in PD patients, is also in line with our results. In contrast, anodal transcranial direct current stimulation (tDCS) of the SMA (thought to induce an excitation) provokes an increase in the APAs developing in the biceps and the triceps brachii during brisk index-finger flexions, without changes in prime mover muscle recruitment and index-finger kinematics [START_REF] Bolzoni | Transcranial direct current stimulation of SMA modulates anticipatory postural adjustments without affecting the primary movement[END_REF]. Lastly, we observed no significant change in balance control during gait after functional inhibition of the SMA suggesting that the SMA is not specifically involved in dynamic postural control while walking, per se, but more in internal representation of sensory information regarding postural status (Jacobs and Horak, 2007). cTBS of the cerebellum produced no marked effects on the spatiotemporal APAs parameters but altered the leg muscle pattern and increased intra-limb muscle co-activation. Our present findings are in line with the fact that anodal tDCS applied to the lateral cerebellum does not modify locomotor patterns, except in the case of adaptive learning [START_REF] Jayaram | Human locomotor adaptive learning is proportional to depression of cerebellar excitability[END_REF][START_REF] Jayaram | Modulating locomotor adaptation with cerebellar stimulation[END_REF], whereas posterior cerebellar disruption provokes maladjustment of sensorimotor calibration with a decoupling between the motor component of the movement (execution) and the afferent sensory information (postural adjustment) [START_REF] Hubsch | Defective cerebellar control of cortical plasticity in writer's cramp[END_REF]) with an alteration of muscle activation pattern with increased co-activation of agonist and antagonist muscles during movement [START_REF] Mari | Lower limb antagonist muscle co-activation and its relationship with gait parameters in cerebellar ataxia[END_REF]. The changes in muscle activation pattern during the APAs or the first step execution induced by cerebellar TBS were probably mediated through the cerebello-thalamo-projections to the motor areas as we targeted lobule VIII of the cerebellum [START_REF] Popa | Long-lasting inhibition of cerebellar output[END_REF], this lobule being activated during sensori-motor tasks [START_REF] Stoodley | Functional topography of the cerebellum for motor and cognitive tasks: an fMRI study[END_REF] in connection with the premotor and motor cortical regions [START_REF] O'reilly | Distinct and overlapping functional zones in the cerebellum defined by resting state functional connectivity[END_REF]. The fact that, in our experiment, cTBS of the cerebellum has little or no effect on postural control suggests that we did not significantly modified vermis or vestibular cerebellum activity [START_REF] Inukai | Influence of Transcranial Direct Current Stimulation to the Cerebellum on Standing Posture Control[END_REF].

We took several precautions to ensure reliable findings. Subjects were randomly assigned to begin with sham, or cerebellar or SMA stimulation to minimise any possible order effects. By having the sessions scheduled at least one week apart we excluded a 'take over' effect. We used a within-subject design and a sham condition to limit the influence of the known large inter-subject variability in susceptibility to develop TBS-induced plasticity [START_REF] Lopez-Alonso | Interindividual variability in response to non-invasive brain stimulation paradigms[END_REF][START_REF] Vallence | Inter-and intra-subject variability of motor cortex plasticity following continuous theta-burst stimulation[END_REF] and stimulation of SMA and the lobule VIII of the cerebellum were both performed under neuro-navigation control. Despite this precaution, we observed changes in gait initiation parameters after sham stimulation. This could have led to underpowered results. An unsolved issue is how to assess the efficacy of the cerebellum or SMA theta-burst stimulation in individuals and consequently, how to determine the sample size needed for such experiments. Stimulation intensity was adjusted according to the individual's motor cortex excitability yet it is unclear to what extent M1 excitability reflects cerebellar or SMA excitability. Lastly, we could not exclude the possibility that stimulation-induced effects on EMG pattern and amplitude occurred by influencing the tonic descending drive exerted on the spinal motoneurones through the descending cerebellar vestibular and reticulospinal tracts.

The fact that cerebellar stimulation with single TMS pulses facilitates the ipsilateral soleus H reflex without increasing the soleus electromyographic activity goes against this hypothesis, however [START_REF] Matsugi | Task dependency of the long-latency facilitatory effect on the soleus H-reflex by cerebellar transcranial magnetic stimulation[END_REF].

Conclusion

In summary, the results support distinct roles for the SMA and the lateral posterior cerebellum in human gait initiation, with the SMA coding for the timing, and probably amplitude, of the preparatory phase of the gait initiation, and the posterior cerebellum contributing to the inter-and intra-limb muscle coordination, and probably coupling between the APAs and the execution phases. Further studies are needed to examine the potential therapeutic effect of such non-invasive cerebral stimulation in patients suffering from SMA or cerebellar dysfunction.

Captions

Figure 1 .Figure 2 .

 12 Figure 1. Biomechanical parameters and leg muscle activity during gait initiation in a control subject. Curves represent the smoothed mean of ten trials and standard deviation. The rectified electromyographic activity of the tibialis anterior (TA) and soleus (SOL) muscles of the swing and the stance legs is shown in the four lower panels. AP: antero-posterior; CoG: centre of gravity; CoP centre of pressure; t0: time of the first biomechanical event; FO1: foot-off of the swing leg; FC1: foot contact of the swing leg; ML: medio-lateral CoP displacement; L: length of the first step; Vm: peak antero-posterior velocity of the centre of gravity; V1: peak negative value of CoG velocity; V2: value of CoG velocity at the time of FC1

  motor area; SOL: soleus muscle; TA: tibialis anterior muscle; TBS : theta burst stimulation.* P<0.05 when compared to before SMA-TBS; ** P<0.05 when compared to before sham-TBS$ P<0.05 when compared to sham TBS.

  soleus muscle; TA: tibialis anterior muscle; TBS : theta burst stimulation.* P<0.05 when compared to before cerebellar-TBS; ** P<0.05 when compared to before sham-TBS.

Figure 1 Figure 2

 12 Figure 1

Table 1 . Effects of SMA theta-burst stimulation on Soleus and Tibialis Anterior muscle activity during the APAs prior to gait initiation in 22 healthy subjects

 1

	SMA cTBS
	Before TBS SMA-TBS	Sham-TBS

Table 2 . Effects of cerebellar theta-burst stimulation on Soleus and Tibialis Anterior muscle activity during the APAs prior to gait initiation in 22 healthy subjects Cerebellar cTBS

 2 TA: tibialis anterior muscle; TBS : theta burst stimulation. * P<0.05 when compared to before SAM-TBS; ** P<0.05 when compared to sham-TBS.

	Before TBS	CER-TBS	Sham-TBS

Table 3 . Effects of SMA theta-burst stimulation on Soleus and Tibialis Anterior muscle activity during first step execution in 22 healthy subjects SMA cTBS

 3

	Before TBS	SMA-TBS Sham-TBS

Table 4 . Effects of cerebellar theta-burst stimulation on Soleus and Tibialis Anterior muscle activity during first step execution in 22 healthy subjects

 4 as mean±SD. CER: cerebellum; RMS: root mean square; SOL:

	Cerebellar cTBS
	Before TBS	CER-TBS	Sham-TBS

Acknowledgements

We thank the Centre for Clinical Investigations (CIC) of the Pitié-Salpêtrière Hospital for administrative support.

ML Welter reports having received research funding from the Brain and Spine

Institute (ICM) and Agence Nationale de la Recherche (ANR) and consulting fees from Medtronic.

Funding source

This work was supported in part by a grant from the Association AMADYS and the Fondation Areva (to A. Richard).

Abbreviations


Keywords: atmospheres, urban ambiances, sensory environment, affective tonality, urban design, perception

In this paper, I propose to explore a new way of designing and experimenting with the city. How are we to conceptualize the changes in contemporary cities on the basis of their ambiances? What about the sensory and emotional production of urban territories? What happens when our aim is no longer just to design space but also to install an atmosphere? Such questions are situated at the intersection of issues of a social, aesthetic, urban, ecological and political nature. I should like to advance a hypothesis: we are currently witnessing what I call the 'setting of ambiance' in urban spaces. To give an account of this phenomenon, I do not intend to offer a formal definition of what an ambiance may be, but rather to show from what it proceeds, on what it is based, what it produces and transforms in urban life. Several ambiance operating modes in the province of urban design will be the focus: establishing the sensory as a field of action, composing with affective tonalities, giving consistency to urban situations, maintaining spaces over time and playing with imperceptible transformations.

We should start by noting the growing attention paid to the sensory dimensions of urban space: lighting plans and sound design; systems to deploy sounds, illumination, air conditioning, ventilation and odours. All these devices work on the sensory matter itself and make the medium the prime basis of design. To put it differently, today's urban ecology increasingly relies on explicit strategies to sensibilize inhabited space. Something we might have taken for granted and certainly occurred in the background -air, sound, odour, heat and light -is becoming one of the basic stakes in urban transformation. Urban development no longer only concerns built forms and spaces, but also sensory environments and climatic envelopes.

This approach, in which the body and senses are allowed to exist, scorns strict disciplinary divisions and operates within a very broad scientific spectrum. Whether one wants to study the fit between the sensory and the social (Augoyard 1979 ;[START_REF] Sansot | Les Formes sensibles de la vie sociale[END_REF][START_REF] Sauvageot | L'épreuve des sens[END_REF][START_REF] Laplantine | Le social et le sensible[END_REF][START_REF] Haroche | L'avenir du sensible[END_REF]), update cultural perception schemata [START_REF] Stoller | The Taste of Ethnographic Things: The Senses in Anthropology[END_REF][START_REF] Classen | Worlds of Sense: Exploring the Senses in History and Across Cultures[END_REF][START_REF] Howes | Sensual Relations. Engaging the Senses in Culture and Social Theory[END_REF][START_REF] Howes | Empire of the Senses. The Sensual Culture Reader[END_REF]Communications 2010), write a history of sensibilities [START_REF] Chartier | La sensibilité dans l'histoire[END_REF][START_REF] Corbin | Le miasme et la jonquille[END_REF], take measure of lived space [START_REF] Frémont | espace vécu[END_REF][START_REF] Tuan | Space and Place[END_REF][START_REF] Seamon | A Geography of the Lifeworld: Movement, Rest and Encounter[END_REF]Rodaway 1994 ;[START_REF] Berque | de milieux en paysage[END_REF]Light and Smith 2004), design architecture for the senses (Pallasmaa 1996 ;[START_REF] Holl | Questions of Perception: Phenomenology of Architecture[END_REF][START_REF] Zumthor | [END_REF][START_REF] Rahm | Architecture météorologique[END_REF]Faces 2010), decipher the sensory dimensions of urban spaces (Lynch 1990 ;[START_REF] Sennett | Flesh and Stone[END_REF]Zardini 2005 ;Paquot 2006, Lucas andMair 2008 ;The Senses & Society 2007 ;Lucas & Mair 2008), rethink the place of the senses in philosophical thought [START_REF] Serres | Les cinq sens[END_REF][START_REF] Berleant | The Aesthetics of Environment[END_REF]Abram 1996 ;[START_REF] Guenancia | L'intelligence du sensible[END_REF]Rancière 2000 ;[START_REF] Stiegler | De la misère symbolique. La catastrophè du sensible[END_REF]), derail common perception through artistic performance (Jones 2006 ;Storr 2007 ;[START_REF] Johnstone | The Everyday[END_REF], focus on the notion of ambiance (Augoyard 1995 ; Amphoux 1998 ; Les Cahiers de la Recherche Architecturale 1998 ; Amphoux, Thibaud, Chelkoff 2004 ;[START_REF] Thibaud | L'horizon des ambiances urbaines[END_REF][START_REF] Thibaud | De la qualité diffuse aux ambiances urbaines[END_REF]Augoyard 2011 ;Thibaud & Siret 2012) or atmosphere [START_REF] Böhme | Atmosphere as the Fundamental Concept of a New Aesthetics[END_REF][START_REF] Böhme | Atmosphäre. Essays zur neuen ästhetik[END_REF]Daidalos 1998 ;[START_REF] Sloterdijk | Sphären I: Blasen[END_REF][START_REF] Sloterdijk | Sphären II: Globen. Makrosphärologie[END_REF][START_REF] Sloterdijk | Sphären III: Schäume. Plurale Sphärologie[END_REF], all involve reference to lived experience and pay particular attention to the sensory register. In brief, a whole collection of paths are open, which intersect and complement each other in the development of a sensory ecology of everyday life in the widest sense of the term. It is as if we are witnessing a fundamental shift that is redefining how we think about the current ambiant world.

The notion of medium is of prime importance here and has been widely developed in communication [START_REF] Mcluhan | Understanding Media. The Extensions of Man[END_REF], psychology [START_REF] Gibson | The Ecological to Visual Approach Perception[END_REF], philosophy [START_REF] Coccia | La Vie sensible[END_REF] and anthropology [START_REF] Ingold | Being Alive. Essays on Movement, Knowledge and Description[END_REF]. It refers to air, sound, light, odour, etc., in other words all the elements of our surroundings which enable us to perceive. It should be perfectly clear that the medium is not what we perceive, not the object of our perception. The medium is the means by which we perceive, it is what makes perception possible. Renaud Barbaras (1998) also demonstrates how sensitive thinking purports to operate a shift: an ontology of the object is replaced by an ontology of the element. Thence "the element is not subjective, nor is it what is perceived. It is the dimension through which perception takes place" (p. 222). There is no vision possible without light, no audition without sound, without a medium for it to propagate and pervade... For example, I do not hear in the same way in a space with a lot of reverberation or, on the contrary, in one that is very muffled. My hearing is not the same underwater or in the open air. I do not see in the same way in a sunlit square as in a thick fog. For perception to occur, there must be a third term between the perceiving subject and the perceived object [START_REF] Böhme | An Aesthetic Theory of Nature : An Interim Report[END_REF]). The medium is the intermediate place starting from which an object becomes perceptible, visible, audible.

By stressing the sensory dimension of in situ experience, the idea of place is forged around a critique of abstract and objective space. Unlike the perception of space as a homogeneous, continuous and divisible expanse along the lines of partes extra partes, a place emanates from a corporal engagement that is indissociable from its powers of guidance and expression. In other words, while there can be no disembodied place, and although body is instantly bound up with place, the latter may not be reduced to a purely formal receptacle nor a system of geographic coordinates. An approach based on embodied place replaces a theory of feature-less space [START_REF] Casey | The Fate of Place. A Philosophical History[END_REF]. Such a venture restores all of the importance of the argument of the intensive and in doing so uncovers one of the features of ambiance. Whereas space is generally perceived as an ensemble of extensive magnitudes, place reintroduces the notion of intensive magnitudes1 . So, space is populated with discrete, enumerable objects or plots: a bench, a door, a wall, a bus shelter, a telephone booth, etc. In terms of number and summation, it is bound up with extensive magnitudes. Its unity arises from a successive juxtaposition of distinct components. Conversely, place engages with sensitive qualities whose varying importance may increase or decline: brightness, heat, roughness, etc.

By acknowledging the existence of the medium and the importance of the intensive, we gain the means to reveal a new field of urban intervention. Henceforward urban design no longer just focuses on objects but also on what is between the objects. It is no longer just a question of designing buildings or megastructures, but also what surrounds them. The medium is consequently not a given, a pure state of nature, but a construct present at every level of design: from ergonomics to architecture, from urbs to territory. In short our purpose is to transform not only a world of built objects and forms, but also a world of air and perceptible atmospheres. It should be clear by now that the whole of the sensory universe is at stake here, not only the strict register of vision.

I stress the present importance of the perceptible domain because it brings into play at least three types of stakes very different in their nature. Setting the ambiance of a space brings into play social and aesthetic issues relating to the quality of life and the well-being of inhabitants. The aim is to create the conditions necessary for a city which is habitable for everyone. But setting the ambiance of a space may also be part of strategies concerned with urban marketing and commercial competition. Sensory marketing or the new scenes of the creative city are good examples of this economic stake. Lastly, setting the ambiance of a space is also an opportunity to contribute to a sustainable environment. In ecological terms, the medium par excellence is air, as in heat pockets and global warming. There is good reason to wonder to what extent the medium's three modes of existence are compatible. How can the air of urban well-being, the air of commercial conditioning and the air of atmospheric pollution succeed in meeting and agreeing?

Composing with affective tonalities

The second operation involves introducing the province of the affect to the composition of urban space. The aim here is to realise the difference between environment and ambiance. In simple terms we might say that ambiance is what gives life to an environment, what confers upon it a value of attachment. To set the ambiance of a territory, we not only need to control the physical parameters of a built environment, but also to endow the territory with a certain character, a specific mood, an emotional and existential value. Any ambiance stirs up past experience and ways of being together.

In other words, the medium to which I referred before is never neutral; rather it always involves specific affective tonalities. We may speak of a 'soothing sonority', an 'unbearable brightness', a 'heady odour', or 'stifling heat'. All these qualities may contribute to ambiance, putting us in a certain bodily and affective state, and engaging our senses. Similarly we may talk of a 'lively' square, a 'gloomy' neighbourhood, a space with a 'chilling', or preferably, 'warm' atmosphere. The keyword in this operation is no longer medium but resonance. Thanks to resonance we are not outside or indifferent to our surroundings, rather we vibrate with, in and through them [START_REF] Nancy | On listening[END_REF]). This resonance is the basis on which unfolds our capacity to affect others and in turn to be affected by them, and more broadly by the ambient world. In other words, ambiance is indistinctly the feeling of self and of the world.

We then need to characterise the notion of ambiance vis-à-vis neighbouring notions. Distinguishing the notion of ambiance from the ones of "landscape" and "situation" stems from a pragmatic approach that is still at the drawing board stage. This is how the chiasmus of ambiances emerges: landscape theories reflect the sensitive qualities of the urban world but remain inoperative most of the time for analysing its practical effectiveness; conversely, action theories stress the practical character of perception but remain immune to its pathic regime.

The advantage of current research into the landscape is that it provides a theoretical framework for analysing the sensitive relationship with the surrounding world. A number of approaches now probe the aesthetic dimension of contemporary urban experience by no longer confining themselves to an analysis of the "natural" landscape and a focus on pictural representation. The perceptive organisation that accompanies the constitution of a landscape does not consist of a purely cognitive activity but also involves feelings. Even though it is closely associated with Romanticism, the idea of Stimmung neatly expresses the intrinsic relationship between the perceptible unity introduced by the landscape and its constitutive feeling [START_REF] Simmel | Philosophie du paysage[END_REF]. Stimmung denotes the overall tonality of a portion of the visible world and ensures the internal coherence of components otherwise considered as disparate and heterogeneous. This focus on the pathic facet of perception and on the world's affective tonalities brings the notion of landscape closer to that of ambiance. However, most aesthetic theories of landscape tend to neglect the practical implications of situated perception as though the experience of landscape necessarily neutralised perspective in action. Placed in a representational space, landscape appears to be based on an essentially contemplative attitude structured around a single fixed point that supposes some necessary perspective vis-à-vis the perceiving subject. However, some research proposes a number of welcome deviations from this dominant conception by tracing alternative perspectives that test the relationship between acting and feeling. Such perspectives are often developed by shifting the modern landscape aesthetic. So, for example, the focus on Japanese culture and landscape design reintroduces mobility and sociability into landscape aesthetics. Notions of "point of mobile perception" highlighting experiments in landscapes in motion, and "flexible conjunction" pointing up appropriate rules and mitate, indicate the use of references setting out shared bases of perception that put the categories inherited from Western philosophy into perspective [START_REF] Nakamura | Tradition paysagère et post-modernité au Japon[END_REF]. A dynamic approach that introduces public participation as a fully-fledged component of the landscape replaces a world vision founded on the idea of the subject. Another way of analysing the recognised categories of modern landscaping consists of testing them using a different, non-visual sensitive process. So when we wonder what a soundscape is, other defining criteria quickly emerge. For Jean-François Augoyard (1995), sonic environment is based more on variable combinations of figure and background than on any stable and durable relationship (metabol), it engages disjointedness rather than spatial continuity and homogeneousness ("discretisation"), and it challenges subject / object dualism in favour of a near/far dynamic. Factoring in the temporal dimension and expressive force of sound favours an impression of immersion of the perceiving subject vis-à-vis its supposed perspective. Lastly, certain poetic approaches introduce the place of the body into landscape experience and invention (Lassus 1995). To a certain extent, this is about rediscovering the immediacy of the relationship with sensitive matter by breaking away as far as possible from the representational world. The focus on a poem's rhythm, intonation and melody demonstrates how the body handles affects and makes itself available to the landscape (Callot 1997). Such perspectives trigger and pave the way for a return to "landscape-centric" thinking: motion tends to replace a fixed point, the social replaces the individual, the corporal replaces the visual, and immersion replaces distancing. Although landscape is usually perceived in contemplative vision mode, these recent contributions have left their mark on action plans and paved the way for a "landscape-in-practice"-type approach (Ingold 2000 ;[START_REF] Joseph | Paysages urbains, choses publiques[END_REF]).

One the other hand, theories of action, particularly those drawing from Anglo-Saxon sociology, are developing as part of dual trend: the increasing focus on the everyday aspects of situated perception and the exploration of street-like behaviour as a research topic. These approaches propose a praxiological model of perception by seeking to understand how everyday situations play out and are conferred with structure and meaning [START_REF] Coulter | The Praxiology of Perception: Visual Orientations and Practical Action[END_REF]. The issue of the relationship between acting and perceiving arises once we attempt to describe social life in terms of its practical accomplishments. These two categories comprise two complementary and indissociable facets of the activity insofar as all theory of practical action inevitably revolves around a conception of situated perception. Conversely, by treating the practical dimension of perception as a priority, this posture tends to neglect its pathic facet. In some ways, theories of action tend to neutralise the phenomenal and qualitative dimensions of the surrounding world.

Nevertheless, certain research provides pointers that could help to get us beyond this aporia. For example, the increasing focus on the role of emotions in how daily exchanges play out aims to get beyond an excessively intellectual view of action (Paperman and Ogien 1995 ;Katz 1999). From this standpoint, the traditional action/passion dichotomy would appear to be under severe strain. Regardless of its interest, such an attempt reflects an essentially cognitive approach and attributes little importance to the whole question of sensitivity. Other research in neuroscience proposes thinking about action in terms of movement [START_REF] Berthoz | The Brain's Sense of Movement[END_REF]. This process sets out to grasp the link between the conative and the cognitive by focusing on the sensory-motor schemes that underpin action. Although returning to this basic level of action facilitates thinking in terms of the affective dimension and the malleability of the gesture, this is at the price of a necessary reduction in the complexity of concrete situations. As such, the micro-ecology of social activities proposes an analytical scale that is definitely suitably adapted to everyday experience (I refer here in particular to the masterful work by Erving Goffman). It not only makes it possible to analyse the material and perceptive framework that structures social interaction, but it also helps distinguish situations according to their affective value. So we refer to "tense" or "relaxed" situations, "embarrassing" or "soothing" situations, "peaceful" or "fraught" situations, etc. However, by giving primacy to expression and human activity, this approach tends to neglect the sensitive components of the built environment. It is as if the sound, light, olfactory or thermal qualities of the ambiant milieu play only a small role in the emergence of the affective tonalities of a given moment.

These few short references show how certain approaches that draw upon theories of action are by no means unrelated to ambiances. By raising the question of emotion, sensory-motor schemes or style of interactions, each in their own way moves towards what we may summarily term the "feeling of the situation".

Based on this appraisal, we may situate ambiance at the juncture of an urban space aesthetic and "pragmatic". The underlying hypothesis is that the notion of ambiance makes it possible to incorporate this dual facet of experience in order to tackle the relationship between acting and feeling from a new angle. Or, to put it more precisely, this ambiance chiasmus consists in striking a balance between the landscape in practice and the feeling of the situation. Such a project necessitates reconsidering how we perceive aesthetics and pragmatism. On the one hand, rather than thinking of aesthetics in terms of taste judgements, we need to do so in terms of aisthesis, i.e., as a discipline focusing on sensoriality itself -on any type of sensitive experience. From this standpoint, it is the relationship between the environmental qualities and human sensitivity that needs to be analysed [START_REF] Böhme | Atmosphäre. Essays zur neuen ästhetik[END_REF]). On the other hand, although pragmatism does indeed deal with human action, it does not have to presuppose an "activist relationship with the world". This version of pragmatism must make it possible to incorporate passivity, sensitivity and receptivity within the same action [START_REF] Joas | The Creativity of action[END_REF]. In a nutshell, the notion of ambiance involves rethinking the relationship between the human organism and its environment by "sensibilising practice".

Setting the ambiance of a space consequently means playing on its affective value. In strictly urban terms this raises the question of the types of affective tonalities to which contemporary urban spaces lend themselves. Today's cities seem to display a dual concern creating a festive spirit while integrating law and order, covering a broad spectrum ranging from the 'ecology of fear' (Mike Davis) to the 'ecology of enchantment' (Christine Boyer). Aesthetics is consequently a major issue for urban governance, the challenge being to find ways of instituting commonality and living in a shared world. In this case, ambiance seems to operate like a two-faced Janus: on the one hand it puts us in contact with others, a condition for the possible feeling of living together; on the other hand it may 'redistribute places and identities' [START_REF] Rancière | The Politics of Aesthetics: The Distribution of the Sensible[END_REF]) -always bearing in mind that resonance is both consonance and dissonance. Some talk of clean urbanism or a new hygienism, to highlight the extent to which the present concern with setting ambiance tends to sideline certain 'undesirable' social groups and affirm the predominance of a particular segment of society. Be that as it may, there is every indication that collective ways of feeling are becoming increasingly directed and supervised.

Giving consistency to urban situations

We have just seen how ambiance differs from environment. We may now explore the pervasive character of ambiance. Any urban situation is made up of a very diverse set of components: ways of walking and talking, games glancing at others or avoiding eyecontact; the prevailing weather and season; built forms and developed space; sound and light quality of place, odours and heat. It is obviously impossible to draw up a complete list. Ambiance does not arise from one or several of these components, nor is it just the sum of their parts. Ambiance cannot be reduced to a type of light or a way of walking, a building material or rainy weather, even if each of these inputs plays an active part in it. Ambiance is more a matter of linking the various components to one another, making them work together and integrating them by giving the same tonality to all that appears. As we may learn from the art world, working on sensory matter consists in giving the world a singular face, a certain overall physiognomy, a particular colour scheme. Thus a single adjective may qualify an ambiance, as being joyful or gloomy, electric or congenial ... The keyword here is coalescence. Saying that ambiance gives consistency to urban situations means affirming the movement of coalescence of the various factors making up a situation. But it is essential to realise that ambiance cannot be precisely located because it has more to do with a pervasive field. It requires an effort to blur our focus, to achieve a floating attention attentive to the way in which a territory weaves links and takes on an internal consistency. The designers of shopping malls are well aware of this, doing everything they can to establish a merchant ambiance: playing carefully prepared background music, maintaining a constant average temperature, with even lighting for optimal showcasing of products, strict control over the rules of behaviour and ways of being, direction of pedestrian streams and spatial layout of merchandise, and so on. All these forms of expression combine, react with and interpenetrate one another to set the ambiance of the place. In this case every effort is made to neutralize the perception of passing time and the existence of a city outside. There reigns a general sense of floating wholly directed towards selling and purchasing.

An ambiance simultaneously summons up all of the senses and distinguishes itself in relation to each one. Should ambiance be expressed in the singular or in the plural? This question has not been resolved at all and highlights the current limits of our understanding of the matter. We may draw upon certain psychological findings to put forward the idea of an original layer of feeling prior to the division of the senses. For instance, Daniel Stern's research into the development of the infant (1985) highlights the existence of traits common to different senses bound up with "vitality affects". Based on a completely different perspective, some research into the ecology of perception challenges the notion of a possible separation of the senses [START_REF] Stoffregen | On specification and the senses[END_REF]. This tends to support the contention of amodal or synesthetic perception. However, each sense possesses a specific spatio-temporal logic that connects us to the world in a specific way. It is therefore impossible to totally undifferentiate sensory registers and to act as if they were all equivalent. On the other hand, can we not consider that each of the senses refers a given ambiance back to a preferential relationship basis? For Eugène [START_REF] Minkowski | Vers une cosmologie[END_REF], ambiance "echos" through hearing, "spreads" through the olfactory, "touches" us through the tactile, etc. Erwin [START_REF] Straus | Erwin Straus « Die Formen des Raümlichen[END_REF] also demonstrates how each sense has its own specific form of spatiality. Should we not admit that on each occasion, ambiance performs a specific, particular summary of the senses? Everything would then become a matter of style. Every way of being could be interpreted as a possible formula for sensitive unity. In this case, if ambiance is actually conjugated in the plural, this plural refers more to styles than to senses. In other words, each ambiance proceeds from a rhythm that gives it its real consistency. It is reality of a rhythmic and energetic order, bound up less with a logic of inclusion than of exposure. By setting the body in motion and then affecting and seizing upon it, ambiance demonstrates powers of impregnation that prevent those who experience it from remaining intact [START_REF] Ghitti | La parole et le lieu. topique de l'inspiration[END_REF]. Everything then becomes a question of force and tension, of degree and intensity, of a specific quality of movement that engages each time our rapport with the ambiant world and expresses the affective tonalities of the moment within the body itself.

Maintaining spaces over time

The fourth operation consists in paying attention to the ordinary condition of urban spaces. In this respect we may distinguish two ways in which ambiance is involved in the composition of a territory. On the one hand it is possible to drum up an ambiance (mettre de l'ambiance) thanks to occasional, exceptional, extraordinary events: a music festival, a sporting event, a street carnival, and so on. Each instance is an opportunity to make the town buzz and to give it a festive character. But it is also possible to set an ambiance (mettre en ambiance) by taking care of the relevant spaces on an everyday basis and over the long term. In the second case, attention does not focus exclusively on the city as a stage, on its most visible, most spectacular components, but also the backdrop, the wings and all that makes up its texture and depth. The keyword here is upkeep.

A small shopkeeper in Tunis sweeps the pavement outside his store every morning, sprinkling it with water to keep it cool. It is a sign of welcome to others which contributes to the upkeep of a shared space and to the overall tonality of the street. So it is not just a question of laying on something outstanding, a memorable event which leaves its mark on the city, but also of paying attention to the little details of a place and taking care of the permanent features of a territory. All too often neglected, urban services play a strategic role here and certainly deserve to be recognized for their full value. A good ambiance is also achieved by efficient management of urban waste, a long-term concern for the state of the road and pavements, constant care for parks and gardens, and so on. Much as with the Tunisian shopkeeper cited above, these services are the guardians of the everyday quality of urban life, all the more important as they are taken for granted.

It should be apparent that this operation which consists in installing an ambiance in a lasting way depends just as much on residents as it does on developers. Ambiance is a shared domain in which professional activities and inhabitant practices are tightly meshed. But caution is required: putting the accent on this often neglected dimension, which hinges on the upkeep of a territory, should not be taken to imply any intention of maintaining a territory in an identical state. There is no question of fixing the city or preserving it in the same state. On the contrary, our concern is to assert that the urban world is undergoing perpetual transformation and that these changes operate in depth, continuously, in an underground manner, accompanying processes at work rather than creating novelty ex nihilo. As Tim [START_REF] Ingold | The Perception of the Environment[END_REF] puts it most accurately: « In dwelling in the world, we do not act upon it, or do things to it; rather we move along with it. Our actions do not transform the world, they are part and parcel of the world's transforming itself. » (p. 200) Taking lasting care of urban spaces consists in keeping them in shape, nourishing sustainable potential, feeding existing resources, bringing together conditions which favour desirable actions, regardless of whether such actions concern urban development professionals or residents. This is how a lasting ambiance may be installed.

It is important to understand that the sensory domain is not an isolated, autonomous domain, disconnected from social practices. On the contrary, any setting of ambiance depends on inhabiting practices which update the resources of the built environment. Everyday activities are a constituent part of ambiance, they contribute to the internal dynamic of an ambiance by revealing the sensory potential of places. But care is nevertheless required: all urban spaces are not identical in this respect. We might refer to the degree of control exerted by and upon an ambiance, in other words its capacity to be responsive to inhabiting practices and expressions. Some urban spaces are more open than others to the public's variations and improvisations. Some leave little room for human manifestations and tend to operate according to a strictly controlling and conditioning rationale. What is at stake here is the capacity of a place to integrate, intensify or neutralize the expressive power of social activities. The well known English anthropologist Gregory Bateson spoke of the necessary 'ecology of flexibility' (Bateson 1972).

Playing with imperceptible transformations

The final operation brings into play an ambiance's power of immersion. The aim here is to show not only how we inhabit a space but also how a space inhabits us. The keyword is impregnation. In simple terms, setting the ambiance of territories consists of a process of impregnation. We would need to develop a complete lexicon to attempt to express this slight but nevertheless vital relation with the ambient environment: from a fragrance to a caress, from a breath to a fleeting touch, from infusion to inclination, from the discreet to the evasive, from je-ne-sais-quoi ('I don't know what') to presque-rien ('almost-nothing') would say Vladimir [START_REF] Jankélévitch | Le je-ne-sais-quoi et le presque-rien[END_REF]. It is certainly easier to illustrate this operation with examples from the art world, when for example a novel transports us with a stream of words to a world of its own, or when music imperceptibly carries us away and infuses us with its atmosphere. We are in the novel, we belong to the music.

As should now be apparent, the process of impregnation is in no way peremptory, massive or final. It is more a matter of engaging in a relation with time and space, a relation made of nuance, slowness and constancy. Let's read the wonderful description given by François Jullien (2011, 49-50):

« When I travel from Paris to Brittany, I often look out of the window of the train as I come closer to the great modification I anticipate. But it always eludes me. At Le Mans we are still in the dependency of Paris and the legendary 'basin' where the landscape remains open. But at Laval we have definitively slipped into a strange, remote land, one that has become secret, in spite of its flatness. And yet there is no demarcation between the two. Is the mutation read in the passage, in the subsoil, from limestone to granite, or from the tiles to the slate on the roofs of the houses, or in the greenness of the meadows, or in the form of the bells or even in the skies, no longer tenderly 'veiled in pink vapours' (Baudelaire), but where the clouds are from that point on structured in dizzying forms, so sharply chiselled by the setting sun? When therefore has the marine element started to appear in the atmosphere or in the life of people? One thing is certain: even if nothing indicates it in the relief, everything has changed before our eyes, without its being perceived, and even to the way the sun sets behind the clouds. A great shattering has occured in the course of the journey without there being a crack to betray it. It is as if nothing has happened. Because this expectancy, or this ambiance, this 'atmosphere', are not demarcated in terms of properties and are therefore impervious to our ontological engagement. » Here we are on the threshold of the perceptible, of what escapes conscious attention, what Leibniz called the 'little perceptions'. The nub of the matter is that ambiance makes us feel rather than making us perceive.

We may now distinguish impregnation from two other relations to territory, injunction and invitation. Injunction is based on a set of manifest constraints, duties and rules, whereas there is nothing immediately explicit about impregnation. Proceeding most of the time by light touches, small inflections and micro-phenomena, impregnation is much more of the order of the pervasive, the infra, the obvious, the already-there. It is as the continuous sound of the ventilation system which I finally erase from my field of consciousness or the stink of pollution which I end up no longer noticing, because it is so omnipresent in the city where I live. All that is needed is for the ventilation to stop or for me to return from a journey to regain awareness of what was already there. Impregnation can also be distinguished from invitation -what James Gibson calls affordance -which operates as a set of resources open for action. Invitation relates to what we are able to do in a specific environment whereas impregnation relates to how one feels within a specific ambiance. It works on the porosity that exists between inhabitants and their surroundings, within our capacity to experience and incorporate small modulations in a perceptible space. Here again, if the sensitive is to be felt, it is above all in a diffuse manner, in terms of affective tonalities. On the one hand, an affective tonality colours the whole of the current situation by conferring it with a certain physiognomy. On the other hand, an affective tonality does not necessarily take hold suddenly and brutally. It proceeds little by little, by slight impregnations made up of minute variations. From this perspective, it is hardly necessary to note or to be aware of it for it to leave its mark on our everyday acts and gestures. So affective tonalities are diffuse because they are non-localisable and infraconscious.

Conclusion

To sum up the various processes which contribute to setting the ambiance of urban spaces, we might say that it is a question of 'setting the tone' of territories. This expression strikes me as fundamental to the questions that concern us, which is the creation of an atmosphere. I have tried to show that setting the tone involves at the same time an art of defocusing, an art of accompaniment and an art of impregnation. What is at stake here is a new way of transforming a familiar, vulnerable world.

As the notion of ambiance becomes a key component in architectural and urban research, it has become urgent to clarify this notion as much as possible. Although every attempt at building up a field of research is necessarily based on an obscure background that cannot be fully explained2 , it is still possible to develop an overview of the related issues and debates. The emergence of this new domain illustrates the increasing interest in sensoriality to think about and produce the built environment. One promising avenue for the notion of ambiance is to offer possibilities for linking and developing a fit between normally disjointed fields. On the one hand, the traditional opposition between experienced-space and designed-space is replaced by a dynamic approach focusing on sensorial methods of structuring space and time. From this standpoint, ambiances analyse spatialisation processes at work in everyday urbanite experiences and in the act of architectural creation. On the other hand, the distinction between theory and practice tends to be attenuated by highlighting the knowledge and know-how of designers as well as by considering the operational impact of scientific approaches. From this standpoint, ambiances summon up diverse models of intelligibility of the sensitive vis-à-vis their practical dimension. The profound changes in urban life bring into play new ways of making territory. Should we not seek in ambiance an alternative to the ontology of things and the primacy of substance? We are surely entering an age of atmospheric phenomena, perceptible envelopes and modified air. May we therefore not speak of the ambient becoming of the contemporary world?

The distinction between extensive and intensive magnitude has been developed in particular by Immanuel Kant in his Critique of pure reason[1781]: "All similar-type reality has a degree (of resistance or weight) that, without any decrease in its extensive magnitude or number, can diminish through infinitely smaller degrees and fade away into nothing. In this way, a dilation that fills space, such as heat, may -without leaving the smallest portion of this space empty -decrease in infinitely smaller degrees, without actually ceasing to fill the space by smaller and smaller degrees, as well as any other more extensive phenomenon."

In this regard, Eugen[START_REF] Fink | Les concepts opératoires dans la phénoménologie de Husserl[END_REF] has observed that "immediacy is always in action in the most extreme forms of reflexivity. Thought itself is based on what we do without hesitating or reflecting. Its productive momentum derives from the unreflected use of these concepts covered in shadows."


Isabelle Mosnier
email: isabelle.mosnier@aphp.fr

Nathalie Mathias

Jonathan Flament

Dorith Amar

Amelie Liagre

Stephanie Borel

Emmanuèle Ambert-Dahan

Olivier Sterkers

Daniele Bernardeschi

Benefit of the UltraZoom Beamforming Technology in Noise in Cochlear Implant Users

INTRODUCTION

Exchange of the sound processor of cochlear implants (CI) allows existing implant recipients to take advantage of any advances in sound processor technology by exchanging or upgrading their current processor to a newer model [1,[START_REF] Seebens | Improvements in speech perception after the upgrade from the TEMPO+ to the OPUS 2 audio processor[END_REF]. Funding of processor upgrade differs from one country to another. Considering the high prices of the processors, the benefit provided by new processors must be demonstrated.

In 2013, Advanced Bionics (AB, Stäfa, Switzerland) introduced the Naída CI Q70 (Naída CI) sound processor. As well as being compatible with the newest AB cochlear implant systems, it was also compatible with the existing HiRes 90K™ and CII™ cochlear implant systems and therefore existing recipients of AB devices, who were using older sound processor types, could be upgraded to the newer technology. In addition to the functions and sound processing technology already available in the previous generation sound processors, the Naída CI introduced an acoustic signal processing beamforming technology called UltraZoom, which was already used in Phonak hearing aids (Nyffeler, Reference Note 1). The intention was to help AB implant recipients to communicate more easily and effectively in noisy environments, which still remains a challenge, even for the best performing recipients [START_REF] Schafer | List equivalency of the AzBio sentence test in noise for listeners with normal-hearing sensitivity or cochlear implants[END_REF].

UltraZoom is an adaptive multi-channel dual-microphone beamformer that focuses on input originating from in front of the listener, while attenuating sounds coming from the sides and from the rear (Fig. 1). It works by exploiting timing and phase differences in the signal arriving at two spatially separated front and back omnidirectional microphones, positioned on top of the processor. The inputs from the two microphones are subtracted from each other, after applying an appropriate delay, and a front-facing directionality pattern is created, reducing input from the rear hemisphere and creating a null point where sounds are completely attenuated. The adaptive nature of UltraZoom allows it to constantly change the directionality of the null, based on the loudest noise source in 33 separate channels, thus suppressing moving noise sources as well as static ones [START_REF] Geißler | Speech reception threshold benefits in cochlear implant users with an adaptive beamformer in real life situations[END_REF].

Previous studies evaluating adaptive beamforming technology with Cochlear Ltd. CI devices have shown that it can significantly improve the perception of speech in noise . Geißler et al. [START_REF] Geißler | Speech reception threshold benefits in cochlear implant users with an adaptive beamformer in real life situations[END_REF] tested UltraZoom as implemented in the Naída CI in 10 subjects, and showed significant improvement in speech perception in noise in a variety of challenging and realistic conditions, when compared to the Harmony sound processor. However, subjects had no take-home experience with the new sound processor and therefore it is not known if they would have been able to transfer these gains shown in the laboratory, into the real world. This is a potential issue for all beamforming technologies, as CI users report smaller subjective benefits than expected from laboratory testing [START_REF] Spriet | Speech understanding in background noise with the two-microphone adaptive beamformer BEAM in the Nucleus Freedom Cochlear Implant System[END_REF]. In part, this may be due to the fact that listeners often find themselves in situations where speech and noise sources are not sufficiently spatially separated, particularly in reverberant environments, which results in cancellation of the speech signal as well as the noise and reduces the signal to noise advantages gained [910,1112]. In the previous studies where subjective measures have been reported, two failed to show a significant improvement in subjective performance with the beamforming technologies using the Speech Spatial Qualities questionnaire, even though the objective results did show a significant benefit [START_REF] Spriet | Speech understanding in background noise with the two-microphone adaptive beamformer BEAM in the Nucleus Freedom Cochlear Implant System[END_REF]910]. Only Mosnier et al. [1] did show a significant improvement in performance in both objective and subjective measures using the Abbreviated Profile of Hearing Aid Benefit (APHAB) [1213],

when subjects using Cochlear Ltd. devices were upgraded to the newer CP810 speech processor with additional directionality.

The objectives of this study were to compare the performance of a group of existing AB cochlear implant users, who were upgraded to the new Naída CI sound processor, in a test of speech perception in noise with and without UltraZoom and to compare their subjective performance with their current sound processor, to their subjective performance after upgrading to the new Naída CI sound processor.

METHODS

Subjects

From February to November 2015, 34 adult subjects aged between 21 and 89 years old (mean 52.8 ± 18.5) were prospectively enrolled in a single tertiary referent referral center. Subjects were required to have at least one CII/HiRes 90K cochlear implant, a postlingual onset of severe-toprofound hearing loss (≥ 6 years of age) and French as their first language. The demographic data of these subjects is presented in Table 1. Nine subjects were unilaterally implanted, 11 bilaterally implanted and 14 were bimodal users with a hearing aid on the contralateral ear. All subjects were experienced CI users (5 to 14.7 years, mean 6.9 ± 1.8) who were due to get a processor upgrade to the Naída CI as part of their routine clinical care. A repeated measures design was used, where subjects acted as their own controls.

Fitting

At the baseline visit, subjects were fitted with a loaner sound processor for the purposes of testing, identical to their current processor. This was to ensure that all microphones were new and ClearVoice algorithm continued to be used with the Naída CI if they had been used with the original processor. They were given a minimum of a two months take-home trial with the Naída CI sound processor, where they were encouraged to use UltraZoom in appropriate situations, where speech was coming from the front and noise from the back and sides of the recipient. The Advanced Bionics SoundWave™ programming software was used and all program parameters remained the same, unless the subject was not happy with the sound quality, in which case alterations to the current clinical program were made accordingly. All bilateral CI users except one were upgraded on both sides.

Speech perception measures

Speech understanding in quiet was evaluated with two lists of seventeen monosyllabic words each (Lafon lists) presented at 60 dB SPL from a source based at one meter in front of the subject. Sentences were presented from a loudspeaker located one meter in front of the subject (0-degree azimuth). Non-correlated stationary speech shaped noise (SSN) was presented at a fixed level of 65 dB SPL simultaneously from all three loudspeakers positioned at +/-90° and 180° to simulate a diffuse noise environment. The level of the speech signal was varied to adjust the signal to noise ratio. A low to moderately reverberant room was used, with a T 60 of around 0.3 seconds.

Subjects were evaluated while listening with the technology that they utilized in their daily environments; participants with a Naída CI processor on one ear and a contralateral hearing aid were tested with both devices together, bilateral participants (two Naída CI processors or one Naída CI processor with another processor type contralaterally) were tested with both devices turned on. The contralateral hearing aid was not fitted or changed during the follow-up period.

At the baseline visit, speech perception was measured with words in quiet with the current sound processor and sentences in noise with the current sound processor and the new Naída CI sound processor in the omnidirectional microphone mode, without UltraZoom. At the follow up visit, two months later, speech perception was measured in quiet with the Naída CI processor without UltraZoom and in noise with the Naída CI sound processor with and without UltraZoom (Table 2). The order of the speech test lists and the test conditions were randomized using a randomization table prepared before the start of the study. At the end of the study the subjects returned home with the new Naída CI sound processor.

Subjective Testing

Subject's self-assessment of their hearing with the different sound processors and programs was recorded using the APHAB [1213]. This 24-item self-assessment inventory requires recipients to report the amount of trouble they are having with communication in various everyday situations.

Benefit is calculated by comparing the recipient's reported difficulty in listening in the specified scenarios. There are four subscales: Ease of Communication (EC), Reverberation (RV), Background Noise (BN), and Aversiveness (AV). Scores are given on a scale from A to G where A is "I always experience this" and G "I never experience this". A percentage score from 1% to 99% is allocated to each category of response to give a mean percentage for each section. The average score for each subsection, recorded at baseline with the previous sound processor, was compared to the average score recorded at the two month follow up visit with the Naída CI sound processor. A global score was also calculated, which is the mean of the scores for all the items in the three EC, RV and BN subscales.

Statistics

The results for each test session were compared independently. Scores for words in quiet and the Matrix sentence test in noise were not normally distributed, so a non-parametric Wilcoxon paired test were was used. Individual scores in quiet were compared using the binomial model described by Thornton and Raffin [18]. The different subsections of the APHAB data were compared using a series of non parametric Wilcoxon tests. A p value of less than 0.05 was considered to be significant, A power calculation showed that in order to detect a difference of 2 dB with sufficient power (80%) and at a significance level of p=0.05, a minimum of 17 subjects was required for the objective testing.

RESULTS

Speech perception testing

When subjects were tested in quiet, there was no difference in group performance between the previous sound processor(s) at baseline and the Naída CI processor(s) in omnidirectional mode after two months use (median score of 53.8% ranging from 5% to 94% and median score of 52.5% ranging from 0% to 97%, respectively) (Wilcoxon paired test, Z=0.37, p>0.05) (Fig. 21).

Analysis of individual scores using the binomial model, described by Thornton and Raffin (1978), showed that four out of the 34 subjects had a significant improvement in scores between the baseline and second test sessions (18). One subject saw a significant reduction in speech score in quiet in the second test session, but scores in noise between sessions did not reflect this. All other subjects had non significant differences between scores of less than 20% (Table 3).

Twenty-one out of the 34 subjects had sufficiently good performance in quiet with the previous sound processor(s) at the initial session to be able to perform the Matrix test in noise (median scores of 64% for monosyllabic words versus 23% in the group of 13 subjects who were not able to perform test in noise). Matrix test at the follow-up session was only performed in this group of 21 patients. At the initial baseline session, there was no significant difference between the recipients' previous sound processor(s) (median SRT of -1.1 dB) and the Naída CI sound processor(s) (median SRT of -1.2 dB) for performance in noise when using the omnidirectional microphone (Wilcoxon paired test, Z=1.01, p>0.05) (Fig. 32A, a lower SRT means a better performance).

At the follow up session, after two months experience with the Naída CI sound processor(s), the median SRT score with Naída CI with UltraZoom was -4 dB (range: +4.8; -10.5 dB) compared to -0.45 dB (range: +6.5; -8.0 dB) with the Naída CI in omnidirectional mode (without Ultrazoom).

The use of UltraZoom significantly improved the median SRT by 3.6 dB (range: +0.5; -7.8 dB) (Wilcoxon paired test, Z=3.91, p<0.0001) (Fig. 32B).

Subjective evaluation

APHAB questionnaires were completed by all 34 subjects. When performance on the APHAB questionnaire was compared across the sessions, significant differences between the scores with the existing sound processor(s) at baseline and the Naída CI sound processor(s) for speech understanding in noisy environments (Wilcoxon paired test, Z=3.57, p<0.001), aversive situations (Wilcoxon paired test, Z=2.10, p<0.05) and globally (Wilcoxon paired test, Z=2.19, p<0.05) were obtained.

When looking at the APHAB outcomes for the group of 21 subjects who were able to perform the Matrix test, a significant improvement when using the Naída CI sound processor(s) compared to the previous processor(s) was found for speech understanding in noisy environments (Wilcoxon paired test, Z= 2.84, p<0.01) and in aversive situations (Wilcoxon paired test, Z= 2.10, p<0.05) (Fig. 43A). For the 13 subjects who were not able to perform the Matrix test at baseline, a significant improvement when using the Naída CI sound processor(s) compared to the previous processor(s) was also shown for speech understanding in noise (Wilcoxon paired test, Z=2.13, p<0.05) (Fig. 43B).

DISCUSSION

This study showed that for the 21 subjects who were able to complete the testing in difficult noisy conditions, the use of UltraZoom provided a significant improvement in performance of 3.6 dB SRT. The diffuse noise test conditions used in this study were designed to be challenging to represent the most common noise condition that CI users encounter in everyday life. The addition of some reverberation in the testing room also helped to simulate a real world condition and is particularly relevant for beamforming technologies as when the target and interfering noise become more spatially diffuse, beamforming performance can degrade [1011, 1112].

Our results were in line with the improvement seen by Geißler et al. [START_REF] Geißler | Speech reception threshold benefits in cochlear implant users with an adaptive beamformer in real life situations[END_REF] in a study evaluating 10 adult Harmony users who had been converted to the Naída CI, but had no take home experience with the new processor. Subjects had been evaluated using the same adaptive test as in our study, but in more challenging conditions with five loudspeakers used to create the noise environment and a higher reverberation time of 0.6s. In our study, twenty-six out of the 34 subjects were using the T-Mic in standard condition which already provides some directionality [6]. Some subjects also used the ClearVoice static noise reduction technology, which in combination with UltraZoom, has been shown to provide the greatest improvement in performance in noise [START_REF] Geißler | Speech reception threshold benefits in cochlear implant users with an adaptive beamformer in real life situations[END_REF]1314]. We choose chose to keep the use of ClearVoice and/or the T-Mic constant across all test conditions and for both sound processor types in order to have no impact on the results.

There is considerable variation in the degree of improvements reported for beamforming technology. In previous studies, when compared to the omnidirectional microphone or the T-Mic, UltraZoom improved speech reception thresholds in noise from 4 up to 9.8 dB in optimum conditions [START_REF] Geißler | Speech reception threshold benefits in cochlear implant users with an adaptive beamformer in real life situations[END_REF]1314] (Advanced Bionics, Reference Note 2). Many factors can explain this variation, such as the speech materials and noise type used, the configuration of the speaker array, the microphone and program configurations compared. In addition, the head alignment of the subject with the speech source can also affect the level of benefits of any adaptive beamformer.

Even though instructions about head position were provided to subjects prior to testing, this is something which remained difficult to control over the whole duration of the session. However, these testing conditions reflected 'real life' conditions and show the wide range what level of benefit a CI user could expect from using this new technology in their daily life. Unfortunately, one of the limitations of adaptive SRT procedures is that a calculation of individual significant SRT differences cannot be made based on the binomial model. The other limitation is that the Matrix test was only performed in the group of the better performers, meaning that we cannot ruled out that some poorer performers from the baseline session were finally able to do the test at the follow-up session. Therefore, no information can be provided on the percentage of subjects whose performance improved significantly when using the beamformer.

The purpose of providing beamforming to CI users is to improve their ability to communicate in the everyday noisy environments we all encounter. Whilst many studies have shown the benefits of this technology in a laboratory setting [START_REF] Geißler | Speech reception threshold benefits in cochlear implant users with an adaptive beamformer in real life situations[END_REF][START_REF] Spriet | Speech understanding in background noise with the two-microphone adaptive beamformer BEAM in the Nucleus Freedom Cochlear Implant System[END_REF]7,[START_REF] Hersbach | Combining directional microphone and single-channel noise reduction algorithms: a clinical evaluation in difficult listening conditions with cochlear implant users[END_REF], a subjective evaluation by subjects is required to show that these benefits can be achieved in real world scenarios. Moreover, the upgrade process was part of the routine clinical practice of the clinic, so both good and poor performers were enrolled. As a result, almost forty percent of the subjects in our study who had poor speech comprehension score in quiet were unable to do the Matrix test in difficult noisy environment before upgrade, but may still have some subjective benefit of the speech processor upgrade. The APHAB results shown here indicate a significant subjective improvement for the listening in background noise, aversiveness and global sections when using the Naída CI sound processor. To check whether the poorer performers benefited from the new sound processor, the APHAB questionnaire was analysed for this particular population and still showed a significant benefit in the background noise section. It is particularly interesting to observe this improvement in poorer performers, for whom the objective improvement could not be shown through the Matrix test. It highlights the importance of evaluating subjective feedback from CI recipients to assess their level of comfort in everyday life. Some previous studies using different subjective measures have been unable to show a subjective benefit along side the laboratory benefits shown [START_REF] Spriet | Speech understanding in background noise with the two-microphone adaptive beamformer BEAM in the Nucleus Freedom Cochlear Implant System[END_REF][START_REF] Hersbach | Combining directional microphone and single-channel noise reduction algorithms: a clinical evaluation in difficult listening conditions with cochlear implant users[END_REF]. Only Mosnier et al. [1] did show a significant benefit on the APHAB when subjects upgraded from the older Cochlear Esprit 3G and Freedom sound processors to the newer CP810. This lack of strong evidence of for any subjective benefits of beamforming is not just an issue for its use in cochlear implants, but is also a criticism for its use with hearing aids [1719]. The subjective results are limited by the fact that the APHAB in common with most of the subjective measurement tools available, relies on asking subjects about predetermined situations, which may not be relevant or equally important to all subjects. An additional limitation of any study where subjects are upgraded to newer technology and cannot be blinded to the sound processor used is that responses may be biased towards the newer technology.

The results of the speech perception testing at baseline show that group performance with the new Naída CI sound processor in noise was the same as with the subjects' existing sound processor when using the same programs and omnidirectional microphone settings. This provides clinicians with confidence that subjects can be upgraded to the Naída CI without a change in performance when used with the standard microphone settings and do not require any training period.

However, the subjects recruited were all using the Harmony sound processor, so these findings can only be applied to recipients who are currently using this sound processor type.

The improvements in recipients' use of beamforming in real world environments may result from a better understanding by clinicians of how to use the technology and appropriately counsel recipients and better implementation of the beamforming algorithm, improving its robustness [9]. Indeed, appropriate counselling on the use of UltraZoom is crucial as recipients are required to manually change the program depending on the listening situation encountered. Therefore, it is important to provide recipients with concrete real life examples of situations where this feature helps speech understanding. However, this might be less relevant with the newest generation of sound processors, which offers automatic selection of the microphone settings depending on the incoming signal i.e. UltraZoom is switched on and off automatically depending on the environment.

To conclude, this study showed that all subjects were successfully upgraded to the new Naída CI Q70 sound processor. Once upgraded, subjects who were able to perform the French Matrix test in noise with their previous processor could take advantage of the UltraZoom beamforming technology on the new sound, so that their ability to communicate in noise was improved.

Ssubjective results with the APHAB questionnaire, confirmed these objective results, showing improvements in median scores in the whole group, but also in the group of poorer performers, for listening in background noise when using the Naída CI Q70 sound processor. This study highlighted the importance of upgrading CI recipients to new technology and of including adaptive tests in noise and subjective feedback evaluation as part of the process.

  working optimally. It was programmed with their current clinical program, including the speech enhancement algorithm ClearVoice™ [1314] as well as the T-Mic™ microphone setting (microphone placed within the concha) [6,1415], if this was used on an everyday basis. They were then upgraded to a new Naída CI sound processor, programmed with the same current clinical program and an identical clinical program plus UltraZoom. The T-Mic microphone and

  Speech understanding in noise was measured with the Matrix sentence test in French [1516], which is an adaptive test based on the Oldenburg sentence test (OlSa) [1617]. The subjects were asked to repeat semantically unpredictable sentences, which always had the same structure: Name, Verb, Number, Common name and Colour. A speech reception threshold (SRT) was automatically measured by adjusting signal to noise ratio until a 50% word understanding score was reached. A lower SRT means a better performance. Prior to testing, at least two practice lists (each containing 20 sentences) were presented to the subject to avoid training effects during the test.

Fig. 1 :Fig. 21 :

 121 FIGURES LEGENDSFig. 1: Polar plot showing UltraZoom performance on KEMAR left ear.

Fig. 32 :Fig. 43 :

 3243 Fig. 32: Performance in noise for the 21 subjects who were able to perform MATRIX test in noise. A. At baseline with the subject's original sound processor(s) and with the Naída CI

Figure 1 Figure 2 Figure 3A

 123A Figure 1

  Figure 3B

Table 2 : Tests conducted at each visit.

 2 Lists of words in quiet with the previous processor (s) -Speech test in noise with signal coming from the front with the previous processor(s) and the Naída CI processor (s) without UltraZoom in a random order -APHAB questionnaire completed with regards to the previous processor(s) use

Baseline -Follow-up at 2 months after Naída CI upgrade -Lists of words in quiet with the Naída CI processor(s) without UltraZoom -Speech test in noise with signal coming from the front with the Naída CI processor(s) with and without UltraZoom in a random order -APHAB questionnaire completed with regards to the Naída CI processor(s) use

Table 3 . Individual scores for speech perception testing in quiet for Lafon words at baseline 403 with the previous sound processor and at the follow-up visit with the Naída CI processor in 404 omnidirectional microphone mode. 405 406 Subject ID Lafon Words Score (%) Subject ID Lafon Words Score (%)

 3

		Previous Processor	Naida Omni		Previous Processor	Naida Omni
	1	37.5	58.5	18	52	55
	2	73	52.5	19	17	29
	3	67	61	20	76	58.5
	4	76	67	21	55.5	82
	5	35	17	22	17	41
	6	23	20	23	85	82
	7	26	43.5	24	14	23
	8	61	49.5	25	5	0
	9	35	38	26	58.5	11
	10	79	73	27	23	14
	11	94	94	28	46.5	52.5
	12	58	58.5	29	11	17
	13	64	52	30	64	79
	14	38	46.5	31	61	70
	15	29	32	32	82	73
	16	32	58	33	35	35
	17	64	67	34	94	97
	407
	408

The authors gratefully acknowledge Solange Lator who collected the data.

Ethical Committee: Informed consent was obtained from each participating subject and ethics approval was given by the French ethical committee: 'Comité de Protection des Personnes -Ilede-France VI'. Subjects obtained no reward or personal gain from taking part in the study. The study was conducted in accordance with the Declaration of Helsinki and followed Good