Robert Lalonde

Catherine Strazielle

Divergent Effects of Haloperidol on Motor Versus Spatial Functions

The effects of haloperidol on motor versus cognitive factors were determined in mice. Haloperidol decreased open-fi eld activity and impaired motor coordination in suspended bar and rotorod tests. The drug also augmented escape latencies in swimming towards submerged or visible goals in the Morris water maze without increasing path length or affecting the probe test of spatial memory. These results indicate that the dopamine-2 receptor blocker can reduce brain activation and impair motor control at doses that leave spatial learning unaffected.

Introduction

Parkinson's disease causes motor and non-motor defi cits mitigated at different degrees with dopamine replacement therapy [START_REF] Spiegel | Performance of repetitive alternating elbow movements in Parkinson's disease[END_REF][START_REF] Aarsland | Mild cognitive impairment in Parkinson's disease[END_REF][START_REF] Leroi | Cognitive and behavioural complications of Parkinson's disease[END_REF]. In addition to the cardinal symptoms of muscle rigidity, akinesia, and resting tremor, patients with Parkinson's disease display postural instabilities. In particular, patients fall more often than controls [START_REF] Allen | Recurrent falls in Parkinson's disease: a systematic review[END_REF]. More worrisome are the fi ndings that patients' loss in postural control respond poorly to the primary treatment, l-dopa [START_REF] Kataoka | Can postural abnormality really respond to levodopa in Parkinson's disease?[END_REF], and that l-dopa even impaired some aspects of it [START_REF] Bonnet | Levodopa has primarily negative infl uences on postural control in patients with Parkinson's disease[END_REF].

Motor and non-motor defi cits have been reproduced in genetic models of Parkinson's disease [START_REF] Dawson | Genetic animal models of Parkinson's disease[END_REF], or after injections of neurotoxic agents that deplete dopamine concentrations in striatum [START_REF] Mehan | Restoration of mitochondrial dysfunction in 6-hydroxydopamine induced Parkinson's disease: a complete review[END_REF]. Moreover, parkinsonian symptoms appear in schizophrenic subjects after high doses of dopamine-2 (D2) receptor antagonists such as chlorpromazine (CPZ) and haloperidol, to a lesser extent the more selective D4 receptor antagonist, clozapine [START_REF] Shin | Drug-induced parkinsonism[END_REF]. In the present study, motor and non-motor effects of haloperidol were examined in mice for exploratory activity in open-fi eld [START_REF] Walsh | The open-fi eld test: a critical review[END_REF], elevated plusmaze [START_REF] Cole | An ethological analysis of the effects of chlordiazepoxide and bretazenil (Ro 16-6028) in the murine elevated plusmaze[END_REF][START_REF] Pellow | Validation of open:closed arm entries in an elevated plus-maze as a measure of anxiety in the rat[END_REF], and emergence [START_REF] Paré | The emergence test: effects of psychotropic drugs on neophobic disposition in Wistar Kyoto (WKY) and Sprague Dawley rats[END_REF] tests, motor coordination in stationary beam, coat-hanger, and rotorod [START_REF] Lalonde | Motor coordination in normal mouse strains and the underlying role of the cerebellar system[END_REF] tests, and spatial learning in the Morris water maze [START_REF] Morris | Place navigation impaired in rats with hippocampal lesions[END_REF][START_REF] Mcnamara | The neuropharmacological and neurochemical basis of place learning in the Morris water maze[END_REF]. In the emergence test, the mice were placed inside a small toy object (orange plastic shoe, length: 13 cm, width: 6 cm, height: 7.5 cm) perforated with 3 holes 3 cm in diameter. This object was situated in the middle of a 41 cm x 27 cm enclosure made of white plastic and surrounded by 18-cm high walls.

Methods

Animals

The mice were not pre-exposed to either apparatus. Latencies before emerging with two or four paws with foot contact on the fl oor of the wider compartment were determined in 2 trials of 5-min separated by 1 hr. Irrespective of whether emergence occurred, the mice were allowed to explore the large enclosure for 10 s. In all three tests of exploratory activity, the apparatus was wiped clean with a damp cloth and dried before evaluating the next mouse. Standard room illumination with white light was used.

The stationary beam (length: 110 cm; diameter: 2 cm; height: 70 cm from a padded surface) made of wood was covered with adhesive tape and separated into 11 segments by line drawings. A piece of cardboard was inserted at each end to prevent any mouse from escaping. The mice were placed in the middle of the beam and the number of segments crossed (4-paw criterion), the latencies before falling, and the number of falls were measured in a single 4-trial session with a 1-min cut-off period and a 15-min intertrial interval.

The triangular-shaped coat-hanger consisted of a horizontal steel wire (diameter: 2 mm, length: 41 cm, height: 38 cm from a padded surface) fl anked by 2 diagonal sidebars (length: 19 cm; inclination: 35° from the horizontal axis). The mice were placed upside-down in the middle of the horizontal wire and released only when all four paws gripped it. Movement times (MTs) before reaching (snout criterion) the fi rst 10 cm segment and the extremity of the horizontal wire were measured, as well as before climbing with 2, 3, or 4 paws and before reaching the midway and top of the diagonal wire. The latencies before falling and the number of falls were also recorded. A trial ended whenever the mice fell or reached the top of the apparatus, from which it was retrieved with a maximal score of 1 min given for latencies before falling. The test was performed in a single 4-trial session with a 1-min cut-off period and a 15-min intertrial interval.

The accelerating rotorod (Letica Rota-Rod/RS, Bioseb, France) was made of striated white perspex (diameter: 3 cm, width: 5 cm; height: 17 cm), providing a fi rm grip, and fl anked at each end by round plates to prevent any mouse from escaping.

The mice were placed on top of the already revolving beam at a speed of 4 rpm and facing away from the experimenter's view in the opposite orientation to beam movement in the longitudinal axis, so that forward locomotion was required for avoiding a fall. The rotorod gradually accelerated from 4 to 40 rpm over the 2-min trial. Latencies before falling were measured in an 8-trial session (4 trial blocks of 2 trials) with a 15-min intertrial interval. When the mice rotated passively for 2 complete turns, they were retrieved and the trials considered as a fall.

The Morris water maze consisted of a basin (diameter: 86 cm, wall height: 30 cm) made of white plastic and fi lled with water (22°C) at a height of 21 cm. Yellow plastic beads were evenly spread over the water surface to camoufl age the escape platform (diameter: 8 cm) made of white plastic and covered with a yellow wire mesh grid to ensure a fi rm grip. The pool was contained in a room with several extramaze visual cues, such as light fi xtures and laboratory instruments. The mice were placed next to and facing the wall successively in north (N), east (E), south (S), and west (W) positions, with the escape platform hidden 1 cm beneath water level in the middle of the NW quadrant. The experimenter followed their swimming trajectories on a videomonitor, on which the image of the pool was separated into 4 equally spaced quadrants.

The quadrant entries (4-paw criterion) and escape latencies were measured in 4-trial sessions for 5 days with a 15-min intertrial interval. The mice remained on the escape platform for at least 5 s. Whenever the mice failed to reach the platform within the 1 min cut-off period, they were retrieved from the pool and placed on it for 5 s. After their swim, the mice were kept dry in a plastic holding cage fi lled with paper towels. The day after the acquisition phase (testing day 6), a probe trial was conducted by removing the platform and placing the mouse next to and facing the N side. The time spent in the previously correct quadrant was measured in a single 1-min trial. One hour later, the visible platform version was evaluated, with the escape platform lifted 1 cm above water level and shifted to the SE quadrant. A 13-cm high pole was inserted on top of the escape platform as a viewing aid. In an identical manner to the place learning task, quadrant entries and escape latencies were measured for 4 trials per session, the animals stayed on the platform for 5 s, and a 1-min cut-off period was imposed with a 15-min intertrial interval, except that the test was conducted in a single day.

Data analyses

The three groups were compared with analyses of variance (ANOVAs) with or without repeated measures followed by pairwise comparisons with PLSD Fisher. Data are presented in mean values ± SEM and statistical signifi cance level set at P=0.05.

Results

Exploratory activity

In the open-fi eld, haloperidol decreased all six facets of motor activity (F2,25>7.6, P < 0.01) except fast rears (F2,25=1.14, P > 0.05), refl ecting in part escape attempts. The 0.1 mg/kg dose reduced the fi ve measures, whereas the 0.05 mg/kg dose reduced two of the fi ve (Table 1). In the elevated plus-maze (Table 1), haloperidol decreased open (F2,25=13.84, P < 0.001) and enclosed (F2,25=22.47, P < 0.001) arm entries without affecting open/total arm entries and duration. The groups did not differ in emergence from the small chamber (Table 1) despite higher latencies for haloperidol, possibly because of high intragroup variances.

Motor coordination

Haloperidol exerted detrimental actions on stationary beam, coat-hanger, and rotorod tests (Table 2 andFigure The haloperidol-induced decrease in fall latencies appeared even worse on the rotorod (F2,25=10.15, P < 0.001), the trial effect being also signifi cant due to rising values as a result of practice (F3,75=11.78, P < 0.001). All these effects were more at the high relative to the low dose.

Spatial learning

Haloperidol increased escape latencies (Figure 2, F2,24=30.4, P < 0.001) but decreased quadrant entries (F2,24=3.8, P < 0.05) in the submerged platform subtask. There was a drug x day interaction on escape latencies (F8,96=8.81, P < 0.001) as a result of the faster placebo group as training proceeded, but only a day effect on quadrant entries as a result of learning (F4,96=30.88, P < 0.001). There was no effect in the probe test (P > 0.05, maximal: 60 s, placebo: 29.7 ± 2.1 s; low-dose haloperidol: 30.8 ± 5.9 s; high-dose haloperidol: 26.3 ± 5.8 s). In the visible platform subtask, haloperidol augmented escape latencies (F2,24=22.7, P < 0.001; summed over 4 trials placebo: 32.0 ± 7.1 s, low-dose haloperidol: 91.3 ± 9.7 s, highdose haloperidol: 115.9 ± 10.1 s) without affecting quadrant entries (placebo: 12.9 ± 1.8, low-dose haloperidol: 13.8 ± 1.2, high-dose haloperidol: 15.6 ± 1.5). Higher escape latencies occurred at both doses.

Discussion

Exploratory activity

Haloperidol reduced horizontal and vertical open-fi eld activity in C57BL/6JIco mice, for fast ambulation at 0.1 mg/kg, for slow ambulation with at a dose as little as 0.05 mg/kg IP.

Likewise, at 0.3 mg/kg SC, haloperidol reduced motor activity in Swiss-Kunming mice [START_REF] Hou | Differential effects of haloperidol, clozapine and olanzapine on learning and memory functions in mice[END_REF], and at 0.1 mg/kg IP in rats [START_REF] Ploeger | Effects of haloperidol on the acquisition of a spatial learning task[END_REF],

as when the drug was injected into the nucleus accumbens [START_REF] Ploeger | Spatial localization in the Morris water maze in rats: acquisition is affected by intra-accumbens injections of the dopaminergic antagonist haloperidol[END_REF].

Such effects are likely mediated by the D2 receptor, perhaps also the D4 receptor, since a more specifi c D4 receptor antagonist, L-745,870, also decreased mouse open-fi eld activity [START_REF] Bristow | L-745,870, a subtype selective dopamine D4 receptor antagonist, does not exhibit a neuroleptic-like profi le in rodent behavioral tests[END_REF].

Higher haloperidol doses are required to cause catalepsy, as for example 2 mg/kg IP in rats [START_REF] Depoortere | SSR181507, a dopamine D2 receptor antagonist and 5-HT1A receptor agonist. II: Behavioral profi le predictive of an atypical antipsychotic activity[END_REF].

Motor coordination

Haloperidol at 0.1 mg/kg IP slowed down rotorod acquisition in C57BL/6JIco mice, the same defi cit found after acute haloperidol administration in Swiss [START_REF] Mabrouk | Endogenous nociceptin/orphanin FQ (N/OFQ) contributes to haloperidol-induced changes of nigral amino acid transmission and parkinsonism: a combined microdialysis and behavioral study in naïve and nociceptin/orphanin FQ receptor knockout mice[END_REF][START_REF] Nayebi | Buspirone improves haloperidolinduced Parkinson disease in mice through 5-HT(1A) receptors[END_REF], and FVB/N [START_REF] Kirschbaum | Rotarod impairment: catalepsylike screening test for antipsychotic side effects[END_REF][START_REF] Kirschbaum | Pharmacodynamic consequences of P-glycoprotein-dependent pharmacokinetics of risperidone and haloperidol in mice[END_REF], mice as well as rats [START_REF] Steinpreis | The effects of atypical antipsychotics and phencyclidine (PCP) on rotorod performance[END_REF][START_REF] Johnson | Neurochemical and motor effects of high dose haloperidol treatment: exacerbation by tryptophan supplementation[END_REF], or rats chronically administered with the drug over a 3-week period [START_REF] Datta | Benefi cial effects of lycopene against haloperidol induced orofacial dyskinesia in rats: possible neurotransmitters and neuroinfl ammation modulation[END_REF][START_REF] Samad | Haloperidol-induced extra pyramidal symptoms attenuated by imipramine in rats[END_REF].

Effective acute doses were 0.03, 0.1, and 0.3 mg/kg IP [START_REF] Steinpreis | The effects of atypical antipsychotics and phencyclidine (PCP) on rotorod performance[END_REF],

0.8 mg/kg IP [START_REF] Mabrouk | Endogenous nociceptin/orphanin FQ (N/OFQ) contributes to haloperidol-induced changes of nigral amino acid transmission and parkinsonism: a combined microdialysis and behavioral study in naïve and nociceptin/orphanin FQ receptor knockout mice[END_REF], 1 mg/kg IP [START_REF] Nayebi | Buspirone improves haloperidolinduced Parkinson disease in mice through 5-HT(1A) receptors[END_REF][START_REF] Kirschbaum | Pharmacodynamic consequences of P-glycoprotein-dependent pharmacokinetics of risperidone and haloperidol in mice[END_REF], but not 0.3 mg/kg IP in ddY mice [START_REF] Nagai | Antipsychotics improve Delta9-tetrahydrocannabinol-induced impairment of the prepulse inhibition of the startle refl ex in mice[END_REF]. The rotorod defi cit appeared even when combined with apomorphine [START_REF] Fenton | Evidence for heterogeneous rotational responsiveness to apomorphine, 3-PPP and SKF 38393 in 6-hydroxydopamine-denervated rats[END_REF]. A rotorod impairment was also reported in Drd2 null mutant mice defi cient for the D2 receptor but linked to the genetic background [START_REF] Kelly | Locomotor activity in D2 dopamine receptor-defi cient mice is determined by gene dosage, genetic background, and developmental adaptations[END_REF]. The defi cit appears with other D2 receptor blockers such as CPZ [START_REF] Gomita | Behavioral effects of HR-592, a new derivative of indole[END_REF][START_REF] Perez-Raya | Changes in chlorpromazine induced CNS effects when associated with other neuroleptics and anxiolytics[END_REF], but the infl uence of D4 receptors must be considered, since selective antagonists, clozapine [START_REF] Park | Pharmacological actions of a novel and selective dopamine D3 receptor antagonist, KCH-1110[END_REF], and L-745,870 [START_REF] Bristow | L-745,870, a subtype selective dopamine D4 receptor antagonist, does not exhibit a neuroleptic-like profi le in rodent behavioral tests[END_REF], also caused rotorod defi cits in mice.

In addition to the rotorod, haloperidol diminished distance travelled on the stationary beam, but in view of open-fi eld decrements, this is likely due to hypoactivity. Haloperidol increased latencies before crossing the stationary beam and footslips in rats [START_REF] Datta | Benefi cial effects of lycopene against haloperidol induced orofacial dyskinesia in rats: possible neurotransmitters and neuroinfl ammation modulation[END_REF]. Haloperidol-induced defects extended to longer MTs and shorter fall latencies in the coat-hanger test.

Spatial learning

Relative to controls, haloperidol in the 0.05-0.1 mg/kg IP range increased escape latencies before reaching the submerged platform while decreasing quadrant entries. Likewise, escape latencies to the submerged platform, not distance swum, rose after haloperidol administration at 0.15 mg/kg PO for 14 days [START_REF] Nowakowska | Some behavioural effects of carbamazepine -comparison with haloperidol[END_REF], 1.0 or 2.0 mg/kg IP for 6 weeks [START_REF] Xu | Chronic haloperidol-induced spatial memory defi cits accompany the upregulation of D(1) and D(2) receptors in the caudate putamen of C57BL/6 mouse[END_REF], or after being dissolved in drinking water for 90 days [START_REF] Terry Av | Differential effects of chronic haloperidol and olanzapine exposure on brain cholinergic markers and spatial learning in rats[END_REF]. In these studies, haloperidol-induced slowing was not accompanied by spatial disorientation as would be the case if path lengths were longer.

In our study, the probe test was unaffected, indicating accurate memory of platform location. As in our study, escape latencies before reaching the submerged platform increased with as low a dose as 0.1 mg/kg SC in Swiss-Kunming mice [START_REF] Hou | Differential effects of haloperidol, clozapine and olanzapine on learning and memory functions in mice[END_REF]. At even lower doses of 0.04 and 0.07 mg/kg IP, haloperidol increased escape latencies in the submerged platform subtask in rats without affecting the visible platform subtask, while 0.1 mg/ kg affected both [START_REF] Ploeger | Effects of haloperidol on the acquisition of a spatial learning task[END_REF], the same effect as in our study at that dose and mimicked when the drug was infused in the nucleus accumbens [START_REF] Ploeger | Spatial localization in the Morris water maze in rats: acquisition is affected by intra-accumbens injections of the dopaminergic antagonist haloperidol[END_REF]. In addition to normal mice and rats, haloperidol deteriorated maze learning in rats with traumatic brain injury [START_REF] Phelps | Divergent long-term consequences of chronic treatment with haloperidol, risperidone, and bromocriptine on traumatic brain injury-induced cognitive defi cits[END_REF][START_REF] Wilson | Haloperidol, but not olanzapine, impairs cognitive performance after traumatic brain injury in rats[END_REF]. A different conclusion may be reached in regard to cognitive versus motor effects on considering that haloperidol at 0.04 mg/kg SC increased the number of rats unable to reach the submerged platform within a minute without slowing down swim speed, while at 0.08 mg/kg both variables were impaired [START_REF] Skarsfeldt | Differential effect of antipsychotics on place navigation of rats in the Morris water maze. A comparative study between novel and reference antipsychotics[END_REF]. However, path length was not measured in that study.

Neuroleptic effects on other spatial paradigms are variable.

On one hand, CPZ impaired delayed spatial discrimination performance [START_REF] Hironaka | Effects of psychoactive drugs on shortterm memory in rats and rhesus monkeys[END_REF], on the other, haloperidol did not affect recognition of familiar versus unfamiliar environments [START_REF] Orsetti | Modifi cation of spatial recognition memory and object discrimination after chronic administration of haloperidol, amitriptyline, sodium valproate or olanzapine in normal and anhedonic rats[END_REF].

Non-spatial learning

Extensive experiments have shown the detrimental impact of neuroleptics on shock avoidance learning. In particular, CPZ impaired the acquisition and performance of active avoidance responses to a conditioned stimulus in rodents [START_REF] Ader | Effects of chlorprozamine on the acquisition and extinction of an avoidance response in the rat[END_REF][START_REF] Crismon | Chlorpromazine and imipramine: parallel studies in animals[END_REF][START_REF] Doty | Effects of age and chlorpromazine on animal memory consolidation[END_REF], and humans [START_REF] Fischman | Effects of chlorpromazine on avoidance and escape responding in humans[END_REF], without affecting shock escape responses. This defect did not extend to brightness discrimination performance motivated by shock [START_REF] Tang | Disruption of brightness discrimination in a shock avoidance task by phencyclidine and its antagonism in rats[END_REF], or the conditioned emotional response [START_REF] Lepore | Effects of low doses of chlorpromazine on a conditioned emotional response in the rat[END_REF]. Yet CPZ delayed acquisition and performance of a lightdark discrimination motivated by water escape [START_REF] Castellano | Lysergic acid diethylamide, amphetamine and chlorpromazine on water maze discrimination in mice[END_REF][START_REF] Castellano | Effects of chlorpromazine and imipramine on discrimination learning, consolidation, and learned behavior in two inbred strains of mice[END_REF]. The deleterious impact included pre-and post-trial administration, indicating interference with memory consolidation.

The infl uence of cognitive factors underlying neuroleptic action can best be ascertained in appetitive as opposed to shock avoidance or water escape paradigms where negative results predominate when injected pre-trial [START_REF] Salamone | The involvement of nucleus accumbens dopamine in appetitive and aversive motivation[END_REF]. CPZ had no effect in rats acquiring simultaneous discriminations for stimulus brightness [START_REF] Telner | Effects of low and moderate doses of chlorpromazine on discrimination learning in the rat[END_REF], or shape despite longer choice latencies at two levels of task diffi culty [START_REF] Lalonde | The effects of chlorpromazine and lithium on appetitive discrimination learning in the rat[END_REF]. Moreover, CPZ had no effect on the acquisition of a simultaneous light-dark discrimination in rat offspring when given to dams from gestation day 17 to 21, though it impaired reversal training [START_REF] Hironaka | Infl uence of maternal chlorpromazine on discrimination learning in rat offspring[END_REF][START_REF] Umemura | Infl uence of chlorpromazine administered to rat dams in the peripartum and nursing periods on the learning behavior of the second generation[END_REF]. Another potent neuroleptic, pimozide, had no effect on the acquisition or perfomance of simultaneous light-dark discrimination learning in food-deprived rats [START_REF] Tombaugh | Effects of pimozide on accuracy of performance and distribution of correct responding on a simultaneous discrimination task in the rat[END_REF][START_REF] Tombaugh | Failure of pimozide to disrupt the acquisition of light-dark and spatial discrimination problems[END_REF], and performance in food-deprived pigeons [START_REF] Tombaugh | Effects of pimozide on nordiscriminated and discriminated performance in the pigeon[END_REF]. However, CPZ impaired visual discrimination performance in pigeons trained with errorfi lled though not errorless trials [START_REF] Terrace | Errorless discrimination learning inthe pigeon: effects of chlorpromazine and impiramine[END_REF], and haloperidol impaired the performance of concurrent object discriminations with 4-hr [START_REF] Turchi | Pharmacological evidence that both cognitive memory and habit formation contribute to within-session learning of concurrent visual discriminations[END_REF], or 24-hr [START_REF] Turchi | Double dissociation of pharmacologically induced defi cits in visual recognition and visual discrimination learning[END_REF], intertrial intervals in monkeys, the former being dependent and the latter independent, respectively, on the limbic system. The drug-induced vulnerability in the monkey task is likely due to added complexity relative to those required in rodents. Yet the infl uence of the limbic system is further indicated by poorer discrimination learning after post-trial intrahippocampal injection of haloperidol in rats [START_REF] Grecksch | The role of dopaminergic mechanisms in the rat hippocampus for the consolidation in a brightness discrimination[END_REF]. Moreover, post-trial IP injections of CPZ slowed down acquisition of a discrimination task in water-deprived rats [START_REF] Ishikawa | Differences in the effects of post-trial chlorpromazine, reserpine, and amphetamine on discrimination learning in rats[END_REF].

Pre-trial neuroleptic administration can also impair limbicdependent recognition memory, as shown by deteriorated matching-to-sample performance between seven geometric symbols in monkeys [START_REF] Ferguson | Acute effects of chlorpromazine in a monkey operant behavioral test battery[END_REF], and two color-matching in pigeons [START_REF] Newland | The effects of chlorpromazine and imipramine on rate and stimulus control of matching to sample[END_REF][START_REF] Watson | Quantifi cation of the effects of chlorpromazine on performance under delayed matching to sample in pigeons[END_REF], though not two color-matching [START_REF] Hironaka | Effects of psychoactive drugs on shortterm memory in rats and rhesus monkeys[END_REF], or clip art and digitized photo non-matching [START_REF] Turchi | Double dissociation of pharmacologically induced defi cits in visual recognition and visual discrimination learning[END_REF], in monkeys.

Although neuroleptics mitigate the impact of reinforcement in operant paradigms requiring lever-presses, response accuracy is mainly unaffected. Primozide was without effect on successive discriminated operant responses distinguishing reinforced from non-reinforced trials for food reward in rats at doses which reduced arousal and the effects of reinforcement [START_REF] Beninger | A comparison of the effects of pimozide and nonreinforcement on discriminated operant responding in rats[END_REF]. Likewise, accuracy in discriminative operant responding of lever choice was normal after administration of haloperidol or CPZ, although clozapine decreased it [START_REF] Picker | Effects of clozapine on fi xed-consecutive-number responding in rats: a comparison to other neuroleptic drugs[END_REF]. Pimozide also declined response rates without affecting choice accuracy in a self-stimulation discrimination paradigm [START_REF] Bowers | Differential effects of pimozide on response-rate and choice accuracy in a selfstimulation paradigm in mice[END_REF]. Moreover, acquisition of a discriminated operant task requiring the adjustment of response rates according to changes in reinforcement schedule was normal in PPP1R1B null mutant mice defi cient in dopamine-and cAMP-regulated neuronal phosphoprotein (DARPP-32), though reversal training was impaired [START_REF] Heyser | DARPP-32 knockout mice exhibit impaired reversal learning in a discriminated operant task[END_REF]. Thus, dopamine blockade prevents reward mechanisms at doses that leave cognition unaffected except when cognitive shifting is required.

In a parallel manner, concept learning was intact in hyperactive children chronically treated with CPZ [START_REF] Freibergs | The effect of chlorpromazine on concept learning in hyperactive children under two conditions of reinforcement[END_REF]. In normal young adult subjects, CPZ impaired the continuous performance task dependent on arousal more than the digit symbol substitution task dependent on executive control [START_REF] Mirsky | On the dissimilar effects of drugs on the digit symbol substitution and continuous performance tests[END_REF], although neuroleptics impaired the latter relative to placebo in young [START_REF] Lynch | The effects of haloperidol on visual search, eye movements and psychomotor performance[END_REF][START_REF] Allain | Effects of risperidone on psychometric and cognitive functions in healthy elderly volunteers[END_REF], and old [START_REF] Allain | Effects of risperidone on psychometric and cognitive functions in healthy elderly volunteers[END_REF], subjects and prevented an intersession practice effect in the young [START_REF] Veselinovic | Effects of antipsychotic treatment on cognition in healthy subjects[END_REF].

  C57BL/6JIco mice were obtained from Charles River, L'Arbresle, France, kept inside group cages with woodchip bedding under a 12/12 hr light-dark cycle, and tested in a separate room. The mice were controlled for age (range 11-15 months) and gender (males only). The research protocol adhered to guidelines of the National Institutes of Health (USA), the European Council Directive (86/609/EEC), and local animal care regulations. Procedure Mice were injected 60 min before the test with haloperidol (Haldol®, 5 mg/ml, Janssen-Cilag), diluted at 0.05 (n=9) or 0.1 mg/kg (n=9) or else saline (n=10) used as the vehicle solution and placebo. One placebo-injected mouse accidently died in the water maze, leaving n=9. The behavioral schedule was presented in randomized orders for different subgroups on weeks 1 and 2, including the following tests: week 1: openfi eld, elevated plus-maze, emergence, week 2 (after 3 days off): stationary beam, coat-hanger, and rotorod. Week 3 included the Morris water maze (testing days 7-12 for all mice). The open-fi eld (Letica model LE 8811, Bioseb, France) contained a 45 x 45 cm sized fl oor made of black perspex and 36 cm high transparent perspex walls. The device distinguished between fast (> 10 cm/s) and slow (< 10 cm/s) ambulatory and stereotyped movements as well as fast and slow rears.Horizontal activity was recorded by infrared photocell detectors with a 2.5 cm intercell distance in the horizontal axis and placed at a height of 1 cm. Vertical activity was recorded by a second row of sensors situated at a height of 5 cm. The mice were placed in the center of the apparatus in a 5-min session. The elevated plus-maze (Letica model LE 840, Bioseb, France) consisted of 4 cross-shaped arms (length: 45 cm, width: 10 cm, height from fl oor: 68 cm) and a 10 cm x 10 cm central region with a fl oor made of black perspex. Two arms were enclosed on three sides by 9-cm high transparent perspex walls while the other two were not. The enclosed arms and the open arms faced each other on opposite sides. Entries (4paw criterion) and time spent in enclosed and open arms were measured, together with open/total arm entry ratios. An entry occurred whenever the mice crossed from one arm to another with 4 paws, re-entries into the same arm from the central region not being counted. The mice were placed in the center, considered as enclosed time until an open arm was entered. Conversely, an entry into an open arm lasted until the mice entered into an enclosed arm. The mice were evaluated in a single 5-min session.

  1). On the stationary beam, haloperidol decreased segments crossed (F2,25=11.97, P < 0.001) without affecting fall latencies or number of falls (P > 0.05). On the coat-hanger, haloperidol increased all MTs (F2,25>3.89, P < 0.05) as well as number of falls (F2,25=4.54, P < 0.05), except MTs to the midway point or top of the diagonal bar (P > 0.05), probably because of a ceiling effect. It also diminished fall latencies (F2,25=5.83, P < 0.01).

Figure 1 :

 1 Figure 1: Effects of 0.05 or 0.1 mg/kg IP haloperidol on acquisition of the rotorod task in s over 4-trial blocks of 2 trials each in mice (mean fall latencies in s summed over trials).

Figure 2a, b :

 b Figure 2a,b: Effects of 0.05 or 0.1 mg/kg IP haloperidol on quadrant entries (A) and escape latencies (B) in s during acquisition of the hidden platform subtask over 5 days in mice (summed values of 4 trials).

Table 1 :

 1 Effects of haloperidol on exploratory activity in mice (means ± SEM).

	Measures	placebo	haloperidol 0.05 mg/kg	haloperidol 0.1 mg/kg
	Open-fi eld Fast ambulation	1344 ± 122	1012 ± 97***	468 ± 71***
	Slow ambulation	213 ± 15	204 ± 7	123 ± 13***
	Fast sterotypies	628 ± 74	682 ± 20	399 ± 47**
	Slow sterotypies	108 ± 5	131 ± 4***	95 ± 4*
	Fast rears	5 ± 1	7 ± 1	4 ± 2
	Slow rears	31 ± 4	26 ± 3	12 ± 2***
	Plus-maze
	Open	5.4 ± 0.5	4.4 ± 0.5	1.9 ± 0.5***
	arm entries
	Enclosed arm entries	10.9 ± 0.9	8.6 ± 0.6***	4.1 ± 0.7***
	Open/total arm entries	33.1 ± 1.2	33.6 ± 2.0	28.3 ± 5.7
	Open arm duration (s)	66.3 ± 8.1	53.9 ± 7.9	52.6 ± 16.4
	Enclosed arm duration (s)	233. 7 ± 8.1	246.1 ± 7.9	247.4 ± 16.4
	Open/total arm duration	22.1 ± 1.7	18.0 ± 2.6	17.5 ± 5.5
	Emergence trial 1	13 ± 2	18 ± 10	60 ± 31
	2-paw/4-paw (s)	14 ± 2	22 ± 11	67 ± 31
	Emergence trial 2	36 ± 7	31 ± 8	73 ± 30
	2-paw/4-paw (s)	52 ± 13	43 ± 14	97 ± 39

*P < 0.05; **P < 0.05 ; ***P < 0.001 vs placebo.

Table 2 :

 2 Effects of haloperidol on motor coordination in mice (means ± SEM).

	Measures	placebo	haloperidol 0.05 mg/kg	haloperidol 0.1 mg/kg
	Stationary beam Segments	81 ± 4	60 ± 9	28 ± 10***
	Fall latencies (s)	237 ± 4	240 ± 0	240 ± 0
	Falls	0.1 ± 0.1	0 ± 0	0 ± 0
	Coat-hanger MT1	52 ± 15	71 ± 17	149 ± 22***
	MT2	113 ± 23	124 ± 24	190 ± 19*
	2-paw MT	162 ± 18	203 ± 12*	228 ± 9**
	3-paw MT	178 ± 15	210 ± 12	233 ± 4**
	4-paw MT	184 ± 14	215 ± 12	234 ± 4**
	Midway MT	201 ± 14	222 ± 8	237 ± 3
	Top MT	214 ± 9	229 ± 7	237 ± 3
	Fall latencies (s)	223 ± 8	220 ± 8	176 ± 15**
	Falls	0.6 ± 0.3	0.8 ± 0.2	1.9 ± 0.4**

*P < 0.05; **P < 0.05 ; ***P < 0.001 vs placebo.


Aude Charollais

S Meyer

Charlene Ponty

Aurélie Lempereur

Marie-Hélène Stumpf

Patrick Berquin

Dorian Bannier

V Laudenbach

Robert Lalonde

Mohammed Rebai

Stumpf Mh

Comparative electrophysiological study of word reading in French: does the P1-N1 temporal window reveal a neurodevelopmental anomaly?

Keywords: Event-related potentials, Reading, Children, Adolescent, P100, N170, P1-N1 wave

des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Introduction

Reading is a human activity that develops as a consequence of genetic predispositions and a stimulating environment. In electrophysiology, variations in certain Event-Related Potentials (ERPs) in response to reading occur as a function of the paradigm Submit your Manuscript | www.austinpublishinggroup.com used. Waves may then reflect, allow to decompose or un-mask verbal and visual networks necessary for reading specialization [START_REF] Goswami | The effects of spelling consistency on phonological awareness: a comparison of English and German[END_REF]. The N170 wavelength appears as a marker of left-side lateralization as the organism matures and acquires reading competence [START_REF] Maurer | Neurophysiology in preschool improves behavioral prediction of reading ability throughout primary school[END_REF]. Its characteristics depend on the reading expertise of the subject and are sensitive to phonological remediation [START_REF] Jucla | Remediation effects on N170 and P300 in children with developmental dyslexia[END_REF]. Its latency, amplitude, and topography also vary as a function of reading exercises. Importantly, it shows inter-individual variability in every language tested [START_REF] Yum | An ERP study of effects of regularity and consistency in delayed naming and lexicality judgment in a logographic writing system[END_REF].

During grapheme-phoneme conversion when learning the alphabet, the left hemisphere specializes in word recognition. This specialization appears refined when comparing ERPs elicited by words and consonant strings (pseudo-words).

N170 varies as a function of the quantity of lexical storage [START_REF] Perfetti | Reading Ability: Lexical Quality to Comprehension[END_REF]. However, with augmenting lexical storage, N170 amplitudes increases only for long or more complex words. The amplitude of N170 varies also as a function of the expertise required to encode phono-alphabetic stimuli, which differentiates adult dyslexics from poor readers [START_REF] Mahé | Is the impaired N170 print tuning specific to developmental dyslexia? A matched reading-level study with poor readers and dyslexics[END_REF]. The stability of the N170 is highly dependent on methodological factors and the type of stimuli used, which renders its interpretation tricky.

In dyslexic children, neural tuning appears delayed and variations in amplitudes and latencies occur. Indeed, N170 characteristics of normal readers at 8 years of age were found in 11-year old dyslexic children [START_REF] Maurer | Impaired tuning of a fast occipito-temporal response for print in dyslexic children learning to read[END_REF]. For the least disabled, a certain form of cognitive economy was possible for frequent words, not different from normal readers but anomalies occurred for decoding processes depending on word length, word frequency and phonological regularity [START_REF] Mahé | Conflict control processing in adults with developmental dyslexia: an event related potentials study[END_REF]. These results may depend on methodological factors such as the type of task used and the nature of the stimuli, even considering that acquisition and automatization of phono-alphabetic coding is dependent on bimodal invariance as proposed by Hebb's law [START_REF] Goswami | The effects of spelling consistency on phonological awareness: a comparison of English and German[END_REF]. Also, interindividual variability may be the result of the specialization of neural networks subtending visual selective attention required for reading and linked to those of oral language and sound representations [START_REF] Dehaene | Illiterate to literate: behavioural and cerebral changes induced by reading acquisition[END_REF]. In other words, it may reflect different neurodevelopmental stages reached by the children before they learn to read.

We previously demonstrated that the N170 response to simple visual stimuli occurred as a function of age [START_REF] Charollais | ERP variabilities as a function of reading maturation[END_REF]. In particular, while P100, P200, and P300 components of ERPs were much larger in adolescent than normal adult readers, no difference was observed for N170 and N230 wavelengths, perhaps due to the fact that the underlying neural tuning has already occurred before adolescence or to the relative easiness of the reading task [START_REF] Charollais | ERP variabilities as a function of reading maturation[END_REF]. Here, we describe the N170 variability in dyslexic adolescents (as compared to normal controls) with the same simple approach, aiming to identify specific N170 variations (as compared to P100, P200 and P300).

Methods

The project was approved by the local ethics committee. Experiments were undertaken at the Regional Center for Learning Disorders. The children were recruited among those consulting for learning problems. An informed consent form was signed by at least one parent. Seventeen dyslexic children were evaluated according to the same procedure as reported previously [START_REF] Charollais | ERP variabilities as a function of reading maturation[END_REF]. Fifteen controls were taken from the general population.

Experiments took place in a dedicated room. The lexical decision task was utilized. Tasks measured by EEG occurred in the dark to fixate the subject's attention on the computer screen. EEG electrodes were connected to an amplifier provided by tMSI (Oldenzaal, the Netherlands). ERPs were recorded with a flexible headset containing 32 electrodes distributed on the scalp according to the international 10-20 system first formulated by Jasper [START_REF] Klem | The ten-twenty system of the International Federation[END_REF]. There were two IBMcompatible computers, one to provide stimuli and the other for data acquisition. The first sent and recorded stimuli via IPRIME software (version 2) and the second collected electrophysiological data or EEG amplified by an amplifier via ASA software (ASA 4.6, ANTNeuro, Enschede, the Netherlands). The impedance of each electrode was verified on ASA software.

For the lexical decision task paradigm, a list of words was presented to the subject as previously reported [START_REF] Charollais | ERP variabilities as a function of reading maturation[END_REF]. The list included words and pseudo-words such as Homo-Phones (HPs) and Written Pseudo-Logatoms (WPLs). HPs are pseudo-words that sound like a real word (e.g. in French « demin » instead of « demain » i.e. « tomorrow »). WPLs are pseudo-words that do not sound like a real word (e.g. « maisson » instead of « maison », i.e. « house »). HPs require an orthographic analysis and WPLs a phonologic analysis. Subjects silently read for 2 min while barring 6 misspelled words. The task consisted of deciding whether a word is real or not among 2-syllable 6-letter words and pseudo-words adapted by us from real words at the following site: www.manulex.org/fr/home.html. Reading speed and reading precision were measured.

Digit Symbol -Coding and Matrix Reasoning subtests of the Wechsler Intelligence Scale for Children-IV were also administered. During Digit-Symbol Coding, subjects copied symbols corresponding to numbers for 2 min, a measure of selective attention and information processing speed. During Matrix Reasoning, a partially filled grid was presented, which had to be completed in a logical manner, a measure of fluid intelligence.

There were 40 blocks of verbal stimuli and a pause every 20 min. Recording and stimulus presentation started at 500 msec, the exposure time was 1 sec, and the maximal allowed time for responding 2 sec.

Statistical analysis

Statistics were run using the Statistica software (Statsoft, Tulsa, CA, US). Comparisons between psycholinguistics (matrices, codes, reading speed, reading precision, leximetry VL ) was performed by ANOVA followed by post hoc analysis by Fischer exact test. A correlation between N170 value and reading speed was searched using Pearson's test.

Results

The results of sixteen dyslexic patients, 12,6±1 years-old (mean±SD), 8 boys, 8 girls, born at term, presenting with a mixed form of dyslexia, predominantly of the phonological type, at various levels of severity were exploited. Subject 17 was maintained in the analysis for all tests except the lexical decision task due to an incomplete compliance with the correct protocol. The group was compared with 15 normal readers (9 boys, 6 girls) controlled for age (13.4±1 years-old (mean±SD) and 17 normal-reading adults (22.8±2 years-old (mean±SD) 10 men, 7 women). Based on reading speed, subjects were subdivided into a severe form of dyslexia with 3 years Submit your Manuscript | www.austinpublishinggroup.com of schooling (n=12, 15.6±1.88 years-old), a moderate form with 4 years of schooling (n=4, 31.25±3.66 years-old), a standard form corresponding to their age level with 8 years of schooling (n=10, mean: 41.6, SD:2.06), a precocious form with 8 years of schooling (n=5, mean:60.6, SD:4.85), and an adult form with 11 years of schooling (n=17, mean: 67.31, SD:2.71). ANOVA revealed a global effect (F (4;42)=119,2; p<0.001) and paired comparisons revealed that each group differed from each (p<0,01) (Table 1) other except the precocious versus the adults at borderline level (p<0.051). Dyslexic subjects were at the lower standard level for the two WISC-IV subtests (Digit-Symbol Coding mean: 10 SD:1.5; Matrix Reasoning mean: 10 SD:1.5; For Matrix Reasoning (mean:12.4, SD:1.2) and Digit-Symbol Coding (mean:13, SD:1.44), precocious children were at the 75 th percentile, at the adult level, whereas standard children were at the average level. As a whole, dyslexic subjects were inferior to precocious and adult subgroups but similar to standard children, as expected from the definition of the anomaly by the World Health Organization.

After eliminating artifacts (-75µv to +75µv) and using grand averaging, we noticed patterns of interest at P7 (left temporo-parietal) and P8 (right temporo-parietal temporo-parietal) electrodes during the lexical decision task for each participant. Irrespective of reading speed, patterns for children contained more positive components than those of adults. The N170 component was absent in severe dyslexia and overlapped the P100 component in some children irrespective of reading speed. The N230 component was always present between 200 and 230 ms. We observed heterogeneity of the N170 component in all groups (Figure 1). No significant difference was detected between N170 patterns in dyslexics and normal readers. Nevertheless, qualitative differences are observable in ERP amplitudes and latencies as well as quantitative differences reflected in inter-individual patterns. We analyzed the positive and negative time course in the 80 to 200 msec range to understand heterogeneity of N170 characteristics (Figure 2). The deviation of the N170 wavelength amid the P100 in all groups performing lexical decisions indicated an association with reading speed in correlation analysis of Pearson test (r=-0,48). The point distribution shows variability in the latency of negativity within the 80-200 ms window in all groups but all the more late as the reading speed (VL) is low. In terms of reading expertise differentiating the groups, the latency distribution before onset of negativity is wider (Figure 3). These results are consistent with the presence of the N170 being superimposed on the P100 in all groups (inter-individual heterogeneity), more so in children. But topographic activity at the 80-200 ms temporal window was more informative in regard to reading activities (Figure 4). The activity of P1-N1 in the 80-200 msec window differentiated normal reading from dyslexic children. In sum, positive and negative activities appeared later and ampler in dyslexic than normal readers for reading simple words in the lexical decision task. The earlier-appearing and less ample positive and negative activities in normal reading children represent a tuning effect.

Discussion

In our entire sample, we report an association between reading speed and the P100-N170 time course as well as reading precision on ERPs, all the more so in dyslexic subjects. The N170 component was variable in these dyslexic subjects, as previously described [START_REF] Maurer | Emerging neurophysiological specialization for letter strings[END_REF]. Variations were masked by the grand averaging method even in normal samples. In non-dyslexic subjects with normal values for reading speed, there was overlap between P100 and N170 wavelengths. Our revealing the P1-N1 interaction may have been due to the fact that stimuli were easy to read even in 7-year-olds. The interaction seems age-related and linked with reading speed and possibly other functional variables. Hasko S showed a diminished area under the curve for the N170 component in developmental dyslexia only for words with false contrasts, interpreted as less efficient encoding relative to normal readers [START_REF] Hasko | What does the brain of children with developmental dyslexia tell us about reading improvement? ERP evidence from an intervention study[END_REF]. Our data take into account intersubject N170 variability and agree with the hypothesis that the N170 wavelength varies along with the P100 wavelength and depends on the nature of verbal stimuli.

Submit your

In addition to these two components, we observed the N230 in all our samples. The N230 wavelength is usually considered to reflect a sub-lexical encoding stage, its presence being explained by the use of our simple stimuli and the schoolwork accomplished by all subjects, including the severely dyslexic group, capable of retrieving common words despite the P1-N1 variability. These results accord with the idea that the P1-N1 relation serves as a dynamic stimulus-dependent variable dependent on maturation. The use of homophones and pseudo-logatoms is relevant in view of previous results presented by Eberhard-Moscicka et al. [START_REF] Jost | Neurocognitive mechanisms of learning to read: print tuning in beginning readers related to word-reading fluency and semantics but not phonology[END_REF] who emphasized the importance of the use of homophones in lexical storage, utilizing a rapid lexical tract as well as phonologic sub-orthographic abilities, a top-down effect [START_REF] Jost | Integration of spoken and written words in beginning readers: a topographic ERP study[END_REF]. In this view, word learning is facilitated by sub-orthographic representations but also by a sufficient lexical storage [START_REF] Gonzalez-Garrido | Orthographic recognition in late adolescents: an assessment through eventrelated brain potentials[END_REF].

The P1-N1 interaction likely develops with time, the P100 reflecting selective attention to visually specific stimuli along with a large N170 component, both diminishing in amplitude with age [START_REF] Hasko | The time course of reading processes in children with and without dyslexia: an ERP study[END_REF]. The N170 is identical for persons reading automatically accessible words and so does not vary as a result of selective attention. However, Submit your Manuscript | www.austinpublishinggroup.com it varies as a function of type of task used, so that the process of automatization may require both components acting together. This idea explains why the N170 wavelength may be mitigated or overlaps the P100 wavelength in slowly developing readers and why dyslexic subjects have a too ample N170 while reading.

The temporal course showed a tendency to be correlated with reading speed, including homophones and written pseudo-logatoms. The natural evolution of the N170, specializing in automatic reading, always diminishes in amplitude and latency with age. Nevertheless, it seems independent of reading quality but rather dependent on early visual extractions underlying the P100 [START_REF] Breznitz | Speed of processing of the visual-orthographic and auditory-phonological systems in adult dyslexics: the contribution of "asynchrony" to word recognition deficits[END_REF]. Thus, simple word reading in our three groups exposes a neurodevelopmental equilibrium between the P100 and the N170 to acquire automatization. These results should of course be evaluated with a larger sample of subjects as well as younger children with different types of reading problems, since the relatively small number of subjects per group limits our study as well as the small number of studies in which French-speaking subjects read very simple words. P1-N1 coupling may thereby serve as a neurodevelopmental marker of the quality of early reading skills independently of age and pathology. Some reports also indicate the There is an inverse correlation trend with reading speed. These results are consistent with the presence of the N170 being superimposed on the P100 in all groups (inter-individual heterogeneity), even more so in children. interdependence of P1-N1 coupling during reading exercises [START_REF] Cao | Early stage visual-orthographic processes predict long-term retention of word form and meaning: a visual encoding training study[END_REF].

Conclusion

Simple word reading during lexical decisions revealed heterogeneous P1-N1 wavelengths on the EEG in phonetic dyslexic subjects that were associated with reading speed, as were normal young and adult readers. The P1-N1 temporal course provides the best estimate of superimposed neural activity and its dynamic relation with a neurodevelopmental disorder. P1-N1 coupling may explain in part inter-individual variability of the N170 by revealing its construction. This early temporal window permits us to test very quickly early visual extraction from words. Precocious children do not have adult ERPs but instead an N170 overlapping the P100. This original result should permit us to test the hypothesis whether simple words provide a strong contrast to unmask specialization of neural networks underlying the reading process. P1-N1 coupling may be seen as a neurodevelopmental marker of reading skill, since it appears at an early age (7/8 years) and occurs rapidly (<200 msec). The correlation between P1-N1 components reflects a top-down pattern during reading automatization. Analysis of this marker may

Figure 1 :

 1 Figure 1: N170 heterogeneity. The N170 component overlapped with the P100 component for child readers reading as quickly as adults. The N170 is not much different between normal reading children and very severe dyslexic children.

Figure 2 :

 2 Figure 2: ERPs of normal reading and dyslexic children. It is noted that P1 and N1 components normally found in the 80 to 170 ms window was not found in the dyslexic brain. Instead, the pattern represents a P1 that overlapped the overall feature of the temporal window to the detriment of the N1.

Figure 3 :

 3 Figure 3: This point distribution shows a variability in the latency of negativity within the 80-200 msec window in all groups.There is an inverse correlation trend with reading speed. These results are consistent with the presence of the N170 being superimposed on the P100 in all groups (inter-individual heterogeneity), even more so in children.

Figure 4 :

 4 Figure 4: Positive and negative activities appeared later and ampler in dyslexic than normal readers for reading simple words in the lexical decision task. The earlier-appearing and less ample positive and negative activities in normal reading children represent a tuning effect.

Table 1 :

 1 Overall statistical results and two to two effect of the population for each test.

	TEST	SC	Degré de	MC	F	p
	VL		20378,78	4	5094,69	119,244	0,00
	HP		3115,95	4	778,99	84,880	0,00
	PLE		7022,40	4	1755,60	73,3525	0,00
	PL		6691,3	4	1672,8	54,745	0,000000
	LUM		21618,6	4	5404,7	45,798	0,000000
	Code		135,872	4	33,968	4,5521	0,003817
	Matrice	143,021	4	35,755	4,9172	0,002417
			COMPARISON 2/2
			VL / silent Read speed
	Reading level	EC Standard childs	EP Precocious Childs	AD Adults	DS severe Dyslexia	DM moderate dyslexia
	EC		0,000004	0,000000	0,000000	0,010565
	EP	0,000004		0,051506	0,000000	0,000000
	AD	0,000000	0,051506		0,000000	0,000000
	DS	0,000000	0,000000	0,000000		0,000169
	DM	0,010565	0,000000	0,000000	0,000169
			LUM/ Oral Reading speed
	Reading level	EC Standard childs	EP Precocious Childs	AD Adults	DS severe Dyslexia	DM moderate dyslexia
	EC		0,628517	0,140724	0,000000	0,001362
	EP	0,628517		0,096078	0,000000	0,011947
	AD	0,140724	0,096078		0,000000	0,000027
	DS	0,000000	0,000000	0,000000		0,000443
	DM	0,001362	0,011947	0,000027	0,000443
			PLE/ Non-word
	Reading level	EC Standard childs	EP Precocious Childs	AD Adults	DS severe Dyslexia	DM moderate dyslexia
	EC		0,000557	0,000000	0,000000	0,072652
	EP	0,000557		0,006590	0,000000	0,000030
	AD	0,000000	0,006590		0,000000	0,000000
	DS	0,000000	0,000000	0,000000		0,000513
	DM	0,072652	0,000030	0,000000	0,000513
			HP/ Homophone
	Reading level	EC Standard childs	EP Precocious Childs	AD Adults	DS severe Dyslexia	DM moderate dyslexia
	EC		0,000008	0,000000	0,000000	0,020599
	EP	0,000008		0,424810	0,000000	0,000000
	AD	0,000000	0,424810		0,000000	0,000000
	DS	0,000000	0,000000	0,000000		0,001408
	DM	0,020599	0,000000	0,000000	0,001408
			COMPARISON 2/2
			PL / reading precision
	Reading level	EC Standard childs	EP Precocious Childs	AD Adults	DS severe Dyslexia	DM moderate dyslexia
	EC		0,066692	0,000145	0,000000	0,082115
	EP	0,066692		0,209133	0,000000	0,003374
	AD	0,000145	0,209133		0,000000	0,000015
	DS	0,000000	0,000000	0,000000		0,000028

Manuscript | www.austinpublishinggroup.com Austin Neurol & Neurosci 2(1): id1019 (2017) -Page -05 Charollais A Austin Publishing Group Submit your Manuscript | www.austinpublishinggroup.com

Submit your Manuscript | www.austinpublishinggroup.com be extended to other populations such as pre-term subjects to explore neural tendencies during reading acquisition.