Coralie Debracque
email: coralie.debracque@unige.ch

Thibaud Gruber

Romain Lacoste

Adrien Meguerditchian

Didier Grandjean

Didier. 1Ψ Grandjean

Cerebral activity in female baboons (Papio anubis) during the perception of conspecific and heterospecific agonistic vocalizations: A functional Near Infrared Spectroscopy study

Keywords: fNIRS, cerebral activity, monkey, agonistic vocalisations, conspecific, heterospecific

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Introduction

Since the 1990s [START_REF] George | Brain Activity during Transient Sadness and Happiness in Healthy Women[END_REF][START_REF] Pihan | The Cortical Processing of Perceived Emotion: A DC-Potential Study on Affective Speech Prosody[END_REF], many neuroimaging studies have investigated the activity of the human temporal cortex during emotional voice processing.

Hence, functional Magnetic Resonance Imaging (fMRI) and more recently functional Near Infrared Spectroscopy (fNIRS) data pointed out the role of the bilateral superior temporal gyrus (STG), superior temporal sulcus (STS) and middle temporal gyrus (MTG) in the processing of emotional prosody [START_REF] Grandjean | Brain Networks of Emotional Prosody Processing[END_REF][START_REF] Grandjean | The Voices of Wrath: Brain Responses to Angry Prosody in Meaningless Speech[END_REF][START_REF] Grandjean | The Voices of Wrath: Brain Responses to Angry Prosody in Meaningless Speech[END_REF][START_REF] Kotz | Predicting Vocal Emotion Expressions from the Human Brain[END_REF][START_REF] Plichta | Auditory Cortex Activation Is Modulated by Emotion: A Functional near-Infrared Spectroscopy (FNIRS) Study[END_REF][START_REF] Wildgruber | A Cerebral Network Model of Speech Prosody Comprehension[END_REF][START_REF] Zatorre | Spectral and Temporal Processing in Human Auditory Cortex[END_REF]) and more specifically in the recognition of positive and negative emotions [START_REF] Bach | The Effect of Appraisal Level on Processing of Emotional Prosody in Meaningless Speech[END_REF][START_REF] Frühholz | Multiple Subregions in Superior Temporal Cortex Are Differentially Sensitive to Vocal Expressions: A Quantitative Meta-Analysis[END_REF][START_REF] Johnstone | The Voice of Emotion: An FMRI Study of Neural Responses to Angry and Happy Vocal Expressions[END_REF][START_REF] Zhang | Speech Prosodies of Different Emotional Categories Activate Different Brain Regions in Adult Cortex: An FNIRS Study[END_REF].

Despite calls for an evolutionary-based approach to emotions that consider the adaptive functions and the phylogenetic continuity of emotional expression and identification [START_REF] Bryant | The Evolution of Human Vocal Emotion[END_REF][START_REF] Greenberg | Evolutionary Perspectives on Emotion: Making Sense of What We Feel[END_REF], few comparative studies have investigated the human temporal cortex activity during the recognition of emotional cues in human voices (conspecific) and other species vocalizations (heterospecific), expressed especially by non-human primates (NHP), our closest relatives [START_REF] Perelman | A Molecular Phylogeny of Living Primates[END_REF]. In the few studies published so far, fMRI conjunction analysis has interestingly identified commonalities in the human cerebral response to human and other animal vocalizations including macaques (Macaca mulatta) and domestic cats (Felis catus). More activations were indeed found in the medial posterior part of the human right orbitofrontal cortex (OFC) during the listening of agonistic vocalizations expressed by both humans and other animals compared to affiliative ones [START_REF] Belin | Human Cerebral Response to Animal Affective Vocalizations[END_REF]). On the contrary, Fritz and colleagues demonstrated a greater involvement of the human STS and the right planum temporale (PT) for the identification of human emotional voices contrasted to chimpanzee (Pan troglodytes) and then macaques calls [START_REF] Fritz | Human Behavioural Discrimination of Human, Chimpanzee and Macaque Affective Vocalisations Is Reflected by the Neural Response in the Superior Temporal Sulcus[END_REF]. Similar results were found in the STS and STG when human emotional voices were compared to various animal sounds, non-vocal stimuli or nonbiological noises [START_REF] Bodin | Functionally Homologous Representation of Vocalizations in the Auditory Cortex of Humans and Macaques[END_REF][START_REF] Pernet | The Human Voice Areas: Spatial Organization and Inter-Individual Variability in Temporal and Extra-Temporal Cortices[END_REF] suggesting a sensitivity of the superior regions of the human temporal cortex but not of the frontal cortex for conspecific voices.

Is this sensitivity of the temporal cortex to emotional cues expressed by conspecifics found in NHP? In other words, are the cerebral mechanisms of vocal emotion perception shared across primate species, or has the auditory cortex of Homo sapiens evolved differently?

The previous literature on primates emphasizes brain continuity between humans and NHP for the auditory processing of conspecific emotions. For instance, fMRI studies in macaques have revealed a greater involvement of the STG for the perception of conspecific emotional calls compared to heterospecific ones including calls from other primate and non-primate species, environmental sounds and scrambled vocalizations [START_REF] Joly | Processing of Vocalizations in Humans and Monkeys: A Comparative FMRI Study[END_REF][START_REF] Ortiz-Rios | Functional MRI of the Vocalization-Processing Network in the Macaque Brain[END_REF][START_REF] Petkov | A Voice Region in the Monkey Brain[END_REF]. Following this, positron emission tomography (PET scan) studies have shown the predominant role of the right PT in chimpanzees [START_REF] Taglialatela | Visualizing Vocal Perception in the Chimpanzee Brain[END_REF]) and of the STS in macaques [START_REF] Gil-Da-Costa | Toward an Evolutionary Perspective on Conceptual Representation: Species-Specific Calls Activate Visual and Affective Processing Systems in the Macaque[END_REF] for the processing of conspecific emotional calls. Additionally, neurobiological findings in macaques and marmosets (Callithrix jacchus) have suggested a greater involvement of the STG and of the primary auditory cortex in the passive listening of emotional conspecific calls compared to environmental sounds, scrambled or time-reversed vocalizations [START_REF] Belin | Voice Processing in Human and Non-Human Primates[END_REF][START_REF] Ghazanfar | The Auditory Behaviour of Primates: A Neuroethological Perspective[END_REF][START_REF] Poremba | Species-Specific Calls Evoke Asymmetric Activity in the Monkey's Temporal Poles[END_REF]). Overall, as for humans, the literature in NHP suggests a sensitivity of the great ape and monkey temporal cortex for the processing of conspecific emotional vocalizations. Despite these results, the question of the specific status of conspecific emotions in NHP remains poorly explored with respect to heterospecific vocalizations. In particular, because of the species-dependent results in humans highlighted above and the phylogenetic proximity across primate species, it seems necessary to include heterospecific stimuli from other NHP to reconstruct the phylogenetic evolution of primate vocal emotion processing [START_REF] Bryant | The Evolution of Human Vocal Emotion[END_REF].

The present study investigated temporal cortex involvement in three female baboons: Talma, Rubis and Chet, during exposure to conspecific vs. heterospecific agonistic vocalizations, using fNIRS. Building on a growing interest over the past decade [START_REF] Boas | Twenty Years of Functional Near-Infrared Spectroscopy: Introduction for the Special Issue[END_REF][START_REF] Pan | Applications of Functional Near-Infrared Spectroscopy in Fatigue, Sleep Deprivation, and Social Cognition[END_REF], we used fNIRS because of its non-invasiveness, its poor sensitivity to motion artefacts [START_REF] Balardin | Imaging Brain Function with Functional Near-Infrared Spectroscopy in Unconstrained Environments[END_REF]) and its suitability for comparative research [START_REF] Debracque | Validating the Use of Functional Near-Infrared Spectroscopy in Monkeys: The Case of Brain Activation Lateralization in Papio Anubis[END_REF][START_REF] Fuster | Near-Infrared Spectroscopy (NIRS) in Cognitive Neuroscience of the Primate Brain[END_REF][START_REF] Kim | Application of Functional Near-Infrared Spectroscopy to the Study of Brain Function in Humans and Animal Models[END_REF][START_REF] Lee | Prefrontal Cortical Activity Associated with Visual Stimulus Categorization in Non-Human Primates Measured with near-Infrared Spectroscopy[END_REF][START_REF] Wakita | Measurement of Neuronal Activity in a Macaque Monkey in Response to Animate Images Using Near-Infrared Spectroscopy[END_REF]. According to the existing literature on NHP and humans suggesting a sensitivity of the primates' temporal cortex for conspecific calls, we expected i) more activation in the temporal cortex for the passive listening of baboon sounds compared to chimpanzee stimuli; and ii) a greater involvement of the temporal cortex for the perception of agonistic conspecific vocalizations in comparison to the other sounds.

Material & Methods

Subjects

The few existing studies using fNIRS in NHP mostly include a single subject [START_REF] Fuster | Near-Infrared Spectroscopy (NIRS) in Cognitive Neuroscience of the Primate Brain[END_REF][START_REF] Wakita | Measurement of Neuronal Activity in a Macaque Monkey in Response to Animate Images Using Near-Infrared Spectroscopy[END_REF]. Three healthy female baboons (Talma -13.5 years old; Rubis -18.4 years old; and Chet -11.8 years old) were included in the present study, contingent with their yearly health check-up; this sample size was consistent with prior work on the perception of affective stimuli by female macaques [START_REF] Lee | Prefrontal Cortical Activity Associated with Visual Stimulus Categorization in Non-Human Primates Measured with near-Infrared Spectroscopy[END_REF]). In addition, as male baboons have large and thick masticatory muscles above their temporal cortex, they were excluded from the experimental protocol. Sexual dimorphism being particularly pronounced in baboons (Phillips-Conroy and Jolly 1981), the female sex was assigned to the subjects based on their facial morphology and red buttocks. Moreover, preventing any ambiguity about the subjects' sex, the three female baboons had already given birth to offspring that they breastfed.

Following this, based on the annual health assessment and the daily behavioural surveys made by the veterinary and animal welfare staff, the subjects had normal hearing abilities and did not present a structural neurological impairment (confirmed with respective T1w anatomical brain images -0.7 x 0.7 x 0.7 resolutioncollected in vivo under anesthesia in the 3Tesla MRI Brunker machine). All procedures were approved by the "C2EA -71 Ethical Committee of neurosciences" (INT Marseille) and performed in accordance with the relevant French law, CNRS guidelines and the European Union regulations. The subjects were born in captivity and housed in social groups at the Station de Primatologie in which they have free access to both outdoor and indoor areas. All enclosures are enriched by wooden and metallic climbing structures as well as substrate on the group to favour foraging behaviours. Water is available ad libitum and monkey pellets, seeds, fresh fruits and vegetables were given every day. The three subjects were lightly anesthetized with propofol and passively exposed to auditory stimuli as described below (see also [START_REF] Debracque | Validating the Use of Functional Near-Infrared Spectroscopy in Monkeys: The Case of Brain Activation Lateralization in Papio Anubis[END_REF] for the complete protocol).

Stimuli

Auditory stimulations consisted of agonistic vocalizations produced by baboon (conspecificsee Figure 1a) and chimpanzee (heterospecificsee Figure 1b) individuals as well as energy matched white noises to control for this low-level acoustic feature and for its unfolding (i.e. the temporal structure of energy of the vocalizations). Aggressor screams and distress calls expressed in an agonistic (i.e. conflictual) context are commonly used in the literature to investigate affective states associated with threat and distress respectively in primate vocalizations [START_REF] Briefer | Vocal Expression of Emotions in Mammals: Mechanisms of Production and Evidence[END_REF][START_REF] Kret | Emotional Expressions in Human and Non-Human Great Apes[END_REF]. More specifically, studies on the baboons' vocal repertoire have shown the link between agonistic vocalizations produced during conflicts and the threatening or distressful emotional state of the caller [START_REF] Kemp | Origins of human language: Continuities and discontinuities with nonhuman primates, Speech Production and Perception[END_REF][START_REF] Seyfarth | Agonistic and Affiliative Signals: Resolutions of Conflict[END_REF].

Each auditory stimulus had a duration of 20 seconds, and was repeated six times (see [START_REF] Debracque | Validating the Use of Functional Near-Infrared Spectroscopy in Monkeys: The Case of Brain Activation Lateralization in Papio Anubis[END_REF] for more details). The auditory stimuli were pseudo-randomized, alternating vocalizations and white noises; and were separated by 15 seconds of silence. Additionally, auditory stimulations were broadcasted either binaurally or monaurally in the right or left ear. chimpanzee vocalizations used as stimuli in the present study. These graphical representations were extracted using the PhonTools package [START_REF] Barreda | phonTools: Tools for Phonetic and Acoustic Analyses [computer program[END_REF] on R. studio (Team 2020).

fNIRS

Recordings

Brain activations were measured using two light and wireless fNIRS devices (Portalite, Artinis Medical Systems B.V., Elst, The Netherlands). Based on tissue transillumination [START_REF] Bright | Reports of Medical Cases Selected with a View of Illustrating the Symptoms and Cure of Diseases by Reference to Morbid Anatomy, Case Ccv[END_REF], fNIRS measures using near infrared lights blood oxygenation changes (e.g. [START_REF] Hoshi | Hemodynamic Signals in FNIRS[END_REF][START_REF] Jöbsis | Noninvasive, Infrared Monitoring of Cerebral and Myocardial Oxygen Sufficiency and Circulatory Parameters[END_REF]) related to the hemodynamic response function constituted of Oxyhemoglobin (O2Hb) and deoxyhemoglobin. fNIRS is a non-invasive technique poorly sensitive to motion artefacts [START_REF] Balardin | Imaging Brain Function with Functional Near-Infrared Spectroscopy in Unconstrained Environments[END_REF]) and fully wearable. The fNIRS optical probes were placed on the right and left temporal cortices of the subjects using T1 MRI scanner images previously acquired at the Station de Primatologie on baboons (see Figure 2). Data were obtained at 50 Hz with two wavelengths (760 and 850 nm) using three measurement, i.e. channels per hemisphere (ch1, ch2, ch3) with three inter-distance probes (3 -3.5 -4 cm) investigating three different cortical depths (1.5 -1.7 -2 cm respectively).

Reducing the potential disturbing impact of the fNIRS protocol on the subjects, each experimental session was planned during the baboons' routine health inspection at the Station de Primatologie. As part of the health check, subjects were isolated from their social group and anesthetized with an intramuscular injection of ketamine (5 mg/kg -Ketamine 1000®) and medetomidine (50µg/kg -Domitor®). Then Sevoflurane (Sevotek®) at 3 to 5% and atipamezole (250 µg/kg -Antisedan®) were administered before recordings. Each baboon was placed in ventral decubitus position on the table and the head of the individual was maintained using foam positioners, cushions and Velcro strips to remain straight and to reduce potential motion occurrences. Vital functions were monitored (SpO2, Respiratory rate, ECG, EtCO2, T°) and a drip of NaCl was put in place during the entire anaesthesia. Before fNIRS recordings, temporal areas on the baboons' scalp were shaved and sevoflurane inhalation was stopped.

Subjects were further sedated with a minimal amount of intravenous injection of Propofol (Propovet®) with a bolus of around 2mg/kg every 10 to 15 minutes or by infusion rate of 0.1 -0.4 mg/kg/min. After the recovery period, subjects were put back in their social group and monitored by the veterinary staff.

Analysis

SPM_fNIRS toolbox [START_REF] Tak | Sensor Space Group Analysis for FNIRS Data[END_REF]) and custom made codes on Matlab 7.4 R2009b (The MathWorks Inc. 2009) were used to perform first level analysis on raw fNIRS data following this procedure: i) O2Hb concentration changes were calculated using the Beer-Lambert law [START_REF] Delpy | Estimation of Optical Pathlength through Tissue from Direct Time of Flight Measurement[END_REF]; ii) motion artifacts were removed manually in each individual and each channel. In total, 10 seconds (1.3%) were removed from the O2Hb signal of Rubis and 35 seconds (4.8%) for Talma and Chet; iii) a low-pass filter based on the HRF [START_REF] Friston | To Smooth or Not to Smooth? Bias and Efficiency in FMRI Time-Series Analysis[END_REF] was applied to reduce physiological confounds; iv) a baseline correction was applied in subtracting the pre-stimulus baseline from the post-stimulus O2Hb concentration changes of each trial and v) O2Hb signal was averaged for Talma in a window of 4 to 12 s post stimulus onset for each trial; and for Rubis and Chet in a window of 2 to 8 s post stimulus onset in order to select the range of maximum O2Hb concentration changes following Debracque et al 2021. Shortly, the differences of concentration range are explained by the presence of tachycardia episodes for both Rubis and Chet during the experiment, involving an HRF almost twice as fast as the one found for Talma.

The second level analysis was made on R. studio (Team 2020) using the permuco package [START_REF] Frossard | Permutation Tests for Regression, ANOVA and Comparison of Signals : The Permuco Package[END_REF]. Through the same data sample, we already demonstrated in [START_REF] Debracque | Validating the Use of Functional Near-Infrared Spectroscopy in Monkeys: The Case of Brain Activation Lateralization in Papio Anubis[END_REF] the robustness of our method and results regarding hemispheric lateralization following motor and auditory stimulations. In the present paper, we wanted to investigate a higher level of brain process, i.e. the perception of conspecific and heterospecific sounds. Hence, in each Hemisphere (right, left), we used non-parametric permutation tests with 5000 iterations to assess O2Hb concentration changes for each subject (Talma, Rubis, Chet) as they enable repeated measures ANOVA in small sample sizes by multiplying the design and response variables (Kherad-Pajouh and Renaud 2015). Stimuli (call, white noise); Species (baboon, chimpanzee); Channels (ch1, ch2, ch3) and Stimulus sides (right, left, both ears) were selected as fixed factors. As recommended, contrast effects of Species and Stimuli within channels were assessed with 2000 permutations (Kherad-Pajouh and Renaud 2015). Both p. values for permutation F (pperm) and parametric F are reported.

Results

First, regarding the subject Talma, permutation tests revealed significant differences of O2Hb concentration changes between the three Channels for the right (F(2,3) = 161.5 , p | pperm <.001) and left hemisphere (F(2,3) = 33.91 , p | pperm <.001). The main factor Species was also found significant for the left hemisphere only (right: F(1,2) = 0.34, p| pperm =.057; left: F(1,2) = 4.24, p| pperm <.05). The main factor Stimuli as well as the interactions Stimuli*Species, Stimuli*Channels, Species*Channels and Stimuli*Species*Channels did not reach significance within the right or left hemisphere (see Supplementary Material). Following these analyses, contrasts within each channel showed that for Talma's left hemisphere, the perception of baboon sounds led to lower O2Hb concentration changes compared to chimpanzee sounds in ch1, ch2 and ch3 (right: F(1,2) = 0.15, p| pperm =.69; left: F(1,2) = 4.07, p| pperm =.05 -see Figure 3a).

Second, for the subject Chet, significant differences of O2Hb concentration changes between the three Channels were found for the right (right: F(2,3) = 3,99 , p | pperm <.05) and left hemisphere (F(2,3) = 25.68 , p | pperm <.001). The main factor Species was also found significant for the right hemisphere only (right: F(1,2) = 5.03, p | pperm <.05; left: F(1,2) = 0.24, p | pperm =.62). Additionally, statistics showed a significant two-way interaction between Stimuli and Species for the left hemisphere only (right: F(1,2) = 0.01 , p | pperm =1; left: F(1,2) = 4.13 , p | pperm =.05). The main factor Stimuli as well as the interactions Stimuli*Channels, Species*Channels and Stimuli*Species*Channels did not reach significance within the right or left hemisphere (see Supplementary Material). Finally, contrasts within each channel revealed that for Chet, while her right hemisphere had a tendency to be more activated for the perception of baboon sounds compared to chimpanzee stimuli in ch1, ch2 and ch3 (right: F(1,2) = 3.74 , p | pperm =.07 ; left: F(1,2) = 0.22 , p | pperm =.65); her left hemisphere had a tendency to be more activated for the passive listening of baboon agonistic calls and chimpanzee white noises when compared to baboon white noises and chimpanzee agonistic calls in ch1, ch2 and ch3 (right: F(1,2) = 0.01 , p | pperm =1; left: F(1,2) = 3.75 , p | pperm =.07 -see Figure 3b).

Third, for the subject Rubis, only a significant difference of O2Hb concentration changes between the three Channels was found for the right hemisphere (right: F(2,3) = 8, 99 , p | pperm <.001; left: F(2,3) = 2.15 , p | pperm =.12 -see Figure 3c). None of the other main effects or interactions reached significance within the left or right hemisphere (see Supplementary material).

Note that for Talma, Rubis and Chet, the factor Stimulus sides (sounds broadcasted either binaurally or monaurally in the right or left ear) did not reach significance and thus, do not statistically explain differences in O2Hb concentration changes underpinning the perception of baboon and chimpanzee sounds by our three subjects (see [START_REF] Debracque | Validating the Use of Functional Near-Infrared Spectroscopy in Monkeys: The Case of Brain Activation Lateralization in Papio Anubis[END_REF] for more details related to auditory asymmetries).

In sum, across the three channels, more O2Hb concentration changes were found in Talma's left temporal cortex for the perception of chimpanzee sounds compared to baboon stimuli. Conversely, for Chet, permutation analyses revealed more O2Hb concentration changes in the right temporal cortex for the passive listening of baboon sounds, especially baboon agonistic calls comparing to chimpanzee stimuli. Additionally, her left temporal cortex was more activated by baboon agonistic calls and chimpanzee white noises than for chimpanzee agonistic calls and baboon white noises. For Rubis, the perception of baboon and chimpanzee sounds did not affect the O2Hb concentration changes of her bilateral temporal cortex. Finally, to the exception of Rubis' left hemisphere, the different cortical depths of the channels (1.5 -1.7 -2 cm) had an impact on the O2Hb measurement of Talma, Chet and Rubis' temporal cortices. [START_REF] Wickham | ggplot2: Create Elegant Data Visualisations Using the Grammar of Graphics [computer program[END_REF]) on R.studio [START_REF] Team | RStudio: Integrated Development for R. RStudio[END_REF] was used for visualizing the data.

Discussion

The present fNIRS study in baboons underlines a highly heterogeneous process for the auditory perception of conspecific and heterospecific affective stimuli.

Using valid statistical methods and analyses [START_REF] Debracque | Validating the Use of Functional Near-Infrared Spectroscopy in Monkeys: The Case of Brain Activation Lateralization in Papio Anubis[END_REF][START_REF] Lee | Prefrontal Cortical Activity Associated with Visual Stimulus Categorization in Non-Human Primates Measured with near-Infrared Spectroscopy[END_REF] as well as the inclusion of three subjects instead of one, as is usually the case in the relevant literature [START_REF] Fuster | Near-Infrared Spectroscopy (NIRS) in Cognitive Neuroscience of the Primate Brain[END_REF][START_REF] Wakita | Measurement of Neuronal Activity in a Macaque Monkey in Response to Animate Images Using Near-Infrared Spectroscopy[END_REF], fNIRS data revealed large inter-individual differences between Talma and Chet for the significant main effect Species. The left temporal cortex of Talma was overall more activated for chimpanzee sounds (calls and white noise) than for baboon ones; in contrast, results were reversed in the right temporal cortex of Chet, where statistical analyses highlighted an increase of O2Hb concentration changes for the passive listening of agonistic baboon sounds, especially baboon agonistic calls compared to chimpanzee sounds. In addition, in her left temporal cortex, we documented an increase in O2Hb concentration led by both the perception of agonistic baboon calls and chimpanzee white noises. No significant results were found for Rubis, although this may have been a consequence of her constant tachycardia during the health check and experiment (see [START_REF] Debracque | Validating the Use of Functional Near-Infrared Spectroscopy in Monkeys: The Case of Brain Activation Lateralization in Papio Anubis[END_REF].

Beyond this apparent absence of congruence in our fNIRS data, our results underlined in fact a highly heterogeneous process for auditory perception in baboons. Well-known in neuroscience research with human participants, inter-individual differences are for instance at play in the location of voice selective areas in human auditory cortex [START_REF] Belin | Voice-Selective Areas in Human Auditory Cortex[END_REF]. In the same line, Pernet and colleagues also demonstrated using fMRI, a great inter-individual variability in the involvement of human STG and STS for the listening of conspecific emotional voices compared to non-vocal sounds [START_REF] Pernet | The Human Voice Areas: Spatial Organization and Inter-Individual Variability in Temporal and Extra-Temporal Cortices[END_REF].

As for humans, the location of the voice selective areas as well as the cortical response of the superior temporal cortex in baboons would be subject to a high heterogeneity. This claim is in line with the results of Xu and colleagues (2019) who have shown in five anaesthetized and awake macaques great inter-individual variabilities in the functional connectivity of different cortical regions [START_REF] Xu | Interindividual Variability of Functional Connectivity in Awake and Anesthetized Rhesus Macaque Monkeys[END_REF].

Interestingly, the authors compared macaques' fMRI data to human ones and concluded on a similar heterogeneity in functional connectivity across primate species. As highly cited human neuroimaging studies (Szucs and Ioannidis 2020), future non-invasive comparative research should include more subjects to take in consideration this inter-individual variability in brain mechanisms. The necessity to increase NHP subjects to address limits in statistical power faces ethical aspects related to animal welfare in the case of invasive neuroimaging studies. The development of fNIRS [START_REF] Debracque | Validating the Use of Functional Near-Infrared Spectroscopy in Monkeys: The Case of Brain Activation Lateralization in Papio Anubis[END_REF] and longitudinal studies in comparative neuroscience [START_REF] Song | Strengths and Challenges of Longitudinal Non-Human Primate Neuroimaging[END_REF]) would thus allow answering parts of these challenges.

Often explored using fMRI or Pet scan (e.g. [START_REF] Bodin | Functionally Homologous Representation of Vocalizations in the Auditory Cortex of Humans and Macaques[END_REF][START_REF] Gil-Da-Costa | Toward an Evolutionary Perspective on Conceptual Representation: Species-Specific Calls Activate Visual and Affective Processing Systems in the Macaque[END_REF][START_REF] Ortiz-Rios | Functional MRI of the Vocalization-Processing Network in the Macaque Brain[END_REF], our fNIRS data remain however inconclusive regarding the processing of conspecific vocalizations compared to white noises. In contrast, comparative research on macaques and marmoset (Callithrix jacchus) showed a greater sensitivity of the temporal cortex in its anterior part than in its posterior area for the contrast conspecific calls vs. control sounds [START_REF] Bodin | Functionally Homologous Representation of Vocalizations in the Auditory Cortex of Humans and Macaques[END_REF]. Future fNIRS studies would help determinate whether this lack of effect replication from our present study might be addressed by improving the probe location on the scalp of baboons and its spatial sensitiveness to this expected effect.

Finally, out of the scope of this paper, permutation test analyses highlighted consistent fNIRS data for the channels 1 and 2 compared to channel 3 on both, right and left hemispheres. This result suggests that, for fNIRS in baboons, the best inter-probe distant to assess cortical activations in temporal cortex would be between 3cm and 3.5cm. Interestingly, these distances are commonly used for fNIRS experiments in human adults [START_REF] Ferrari | A Brief Review on the History of Human Functional Near-Infrared Spectroscopy (FNIRS) Development and Fields of Application[END_REF].

To conclude, our fNIRS data mainly pointed out the existence of a highly heterogonous process across individuals for the perception of conspecifics emotional vocalizations in baboons. Whereas such an inter-individual heterogeneity is also well documented in humans, we do thus not excluded a potential phylogenetic continuity with non-human primates in the brain processing of conspecific emotional vocalizations which might be inherited from our common ancestor. Our results remain however inconclusive, notably in regards to the lack of contrasts conspecific agonistic vocalizations vs. white noises (control sounds), which are often explored meaningfully using fMRI or Pet scan (e.g. [START_REF] Bodin | Functionally Homologous Representation of Vocalizations in the Auditory Cortex of Humans and Macaques[END_REF][START_REF] Gil-Da-Costa | Toward an Evolutionary Perspective on Conceptual Representation: Species-Specific Calls Activate Visual and Affective Processing Systems in the Macaque[END_REF][START_REF] Ortiz-Rios | Functional MRI of the Vocalization-Processing Network in the Macaque Brain[END_REF]. This highlights one of the limitations of our study. fNIRS, Pet scan and fMRI measure hemodynamic changes, however the later have a much higher spatial resolution [START_REF] Gosseries | Functional neuroimaging (fMRI, PET and MEG): what do we measure?[END_REF]) than fNIRS [START_REF] Scholkmann | A Review on Continuous Wave Functional Near-Infrared Spectroscopy and Imaging Instrumentation and Methodology[END_REF]. Secondly, another limitation is that our experiment focused on baboons and it is unclear whether it will replicate in other NHP species such as Americas' monkeys. In fact, [START_REF] Fitch | Primate Laterality and the Biology and Evolution of Human Handedness: A Review and Synthesis[END_REF] have already suggested differences between monkeys in terms of mechanisms for the processing of conspecific and heterospecific vocalizations [START_REF] Fitch | Primate Laterality and the Biology and Evolution of Human Handedness: A Review and Synthesis[END_REF]. A final limitation of our study is that only agonistic vocalizations were included in the present fNIRS protocol. Similarly to humans, NHP might have some distinctive brain mechanisms for negative and positive emotions (e.g. [START_REF] Davidson | Anterior Cerebral Asymmetry and the Nature of Emotion[END_REF][START_REF] Frühholz | Multiple Subregions in Superior Temporal Cortex Are Differentially Sensitive to Vocal Expressions: A Quantitative Meta-Analysis[END_REF][START_REF] Zhang | Speech Prosodies of Different Emotional Categories Activate Different Brain Regions in Adult Cortex: An FNIRS Study[END_REF].

Overall, our study does not exclude the existence of common evolutionary roots for auditory processing across primate species to explain the inter-individual variability generally reported in those studies and underlines the importance of comparative research in monkeys to understand brain mechanisms at play in modern humans.

Figure 1 :

 1 Figure 1: Representative waveforms and spectrograms of 20s-long agonistic a) baboon and b)

Figure 2 :

 2 Figure 2: fNIRS optode and channel locations according to 89 baboons T1 MRI template (Love et al. 2016). Blue and green crosses represent optical receivers and transmitters respectively. Ch1, Ch2 and Ch3 indicate the three channels on the right and left temporal cortex.

Figure 3 :

 3 Figure 3: Right and left temporal cortex activations for the baboons a) Talma, b) Chet and c) Rubis during the perception of agonistic baboon (conspecific) and chimpanzee (heterospecific) vocalizations as well as their energy matched white noises. The mean concentration changes of O2Hb (y axis) are represented in micro molar (µM) for each fNIRS channel (x axis). Colourful dots and dark lines represent stimuli and confidence intervals respectively. Results of the permutation tests within channels are shown with * p<.05; p=.07. The ggplot2 package[START_REF] Wickham | ggplot2: Create Elegant Data Visualisations Using the Grammar of Graphics [computer program[END_REF]) on R.studio[START_REF] Team | RStudio: Integrated Development for R. RStudio[END_REF]

Acknowledgements

We thank the Swiss National Foundation and the European Research Council for funding this work.

We warmly thank the vet Pascaline Boitelle, the animal care staff as well as Jeanne Caron-Guyon, Lola Rivoal, Théophane Piette and Jérémy Roche for assistance during the recordings. CD also thanks Dr.

Ben Meuleman for his wise advices on permutation test analyses.

Declarations

Funding

This work was supported by the Swiss National Science Foundation (SNSF, grant P1GEP1_181492 to CD), the European Research Council (grant 716931 -GESTIMAGE -ERC-2016-STG to AM) as well as the French grant "Agence Nationale de la Recherche" (ANR-16-CONV-0002, ILCB to AM) and the Excellence Initiative of Aix-Marseille University (A*MIDEX to AM). TG was additionally supported by a career grant of the SNSF during the final writing of this article (grant PCEFP1_186832).

Availability of data and material

Raw data are freely available to any researcher.

Code availability

Custom Matlab and R. studio codes are available on request.

Conflict of interest

The authors have no conflicts of interest to declare that are relevant to the content of this article.

Ethics approval

All animal procedures were approved by the "C2EA -71 Ethical Committee of neurosciences" (INT Marseille) under the application number APAFIS#13553-201802151547729, and were conducted at the Station de Primatologie CNRS (UPS 846, Rousset-Sur-Arc, France) within the agreement number C130877 for conducting experiments on vertebrate animals. All methods were performed in accordance with the relevant French law, CNRS guidelines and the European Union regulations (Directive 2010/63/EU).

Consent to participate

Not applicable.

Consent for publication

Not applicable.


Coralie Debracque
email: coralie.debracque@unige.ch

Thibaud Gruber

Romain Lacoste

Adrien Meguerditchian

Didier Grandjean

Didier. 1Ψ Grandjean

Cerebral activity in monkeys Papio anubis during the perception of conspecific and heterospecific agonistic vocalizations: A functional Near Infrared Spectroscopy study

Keywords: fNIRS, cerebral activity, monkey, agonistic vocalisations, conspecific, heterospecific

published or not. The documents may come

Introduction

Since the 1990s [START_REF] George | Brain Activity during Transient Sadness and Happiness in Healthy Women[END_REF][START_REF] Pihan | The Cortical Processing of Perceived Emotion: A DC-Potential Study on Affective Speech Prosody[END_REF], many neuroimaging studies have investigated the human temporal cortex activity in emotional voice processing. Hence, functional Magnetic Resonance Imaging (fMRI) and more recently functional Near Infrared Spectroscopy (fNIRS) data pointed out the role of the bilateral superior temporal gyrus (STG), superior temporal sulcus (STS) and middle temporal gyrus (MTG) in the processing of emotional prosody [START_REF] Grandjean | Brain Networks of Emotional Prosody Processing[END_REF][START_REF] Grandjean | The Voices of Wrath: Brain Responses to Angry Prosody in Meaningless Speech[END_REF][START_REF] Grandjean | The Voices of Wrath: Brain Responses to Angry Prosody in Meaningless Speech[END_REF][START_REF] Kotz | Predicting Vocal Emotion Expressions from the Human Brain[END_REF][START_REF] Plichta | Auditory Cortex Activation Is Modulated by Emotion: A Functional near-Infrared Spectroscopy (FNIRS) Study[END_REF][START_REF] Wildgruber | A Cerebral Network Model of Speech Prosody Comprehension[END_REF][START_REF] Zatorre | Spectral and Temporal Processing in Human Auditory Cortex[END_REF]) and more specifically in the recognition of positive and negative emotions [START_REF] Bach | The Effect of Appraisal Level on Processing of Emotional Prosody in Meaningless Speech[END_REF][START_REF] Frühholz | Multiple Subregions in Superior Temporal Cortex Are Differentially Sensitive to Vocal Expressions: A Quantitative Meta-Analysis[END_REF][START_REF] Johnstone | The Voice of Emotion: An FMRI Study of Neural Responses to Angry and Happy Vocal Expressions[END_REF]Zhang, Zhou, and Yuan 2018).

Yet, despite calls for an evolutionary-based approach to emotions that consider the adaptive functions and the phylogenetic continuity of emotional expression and identification [START_REF] Bryant | The Evolution of Human Vocal Emotion[END_REF][START_REF] Greenberg | Evolutionary Perspectives on Emotion: Making Sense of What We Feel[END_REF], few comparative research investigated the human temporal cortex activity during the recognition of emotional cues in human voices (conspecific) and other species vocalizations (heterospecific), expressed especially by non-human primates (NHP), our closest relative [START_REF] Perelman | A Molecular Phylogeny of Living Primates[END_REF]. In the few studies published so far, fMRI analysis has revealed more activations in human auditory cortex for the recognition of agonistic vocalizations expressed by humans as well as macaques (Macaca mulatta) and domestic cats (Felis catus) comparing to affiliative ones. This result was largely driven by a decrease of activity in auditory cortex during the listening of macaque and cat vocalizations compared to human vocalizations [START_REF] Belin | Human Cerebral Response to Animal Affective Vocalizations[END_REF]. Additionally, Fritz and colleagues demonstrated a greater involvement of the human STS and the right planum temporale (PT) for the identification of human emotional voices contrasted to chimpanzee (Pan troglodytes) and then macaques calls [START_REF] Fritz | Human Behavioural Discrimination of Human, Chimpanzee and Macaque Affective Vocalisations Is Reflected by the Neural Response in the Superior Temporal Sulcus[END_REF]. Interestingly, similar results were found in the STS and STG when human emotional voices were compared to various animal sounds, non-vocal stimuli or non-biological noises [START_REF] Bodin | Functionally Homologous Representation of Vocalizations in the Auditory Cortex of Humans and Macaques[END_REF][START_REF] Pernet | The Human Voice Areas: Spatial Organization and Inter-Individual Variability in Temporal and Extra-Temporal Cortices[END_REF] suggesting a specific sensitivity of the superior regions of the human temporal cortex for conspecific voices.

Is this sensitivity of the temporal cortex to emotional cues expressed by conspecific found in NHP? In other words, are the cerebral mechanisms of vocal emotion perception shared across primate species, or has the auditory cortex of Homo sapiens evolved differently?

The previous literature on primates emphasizes the brain continuity between humans and NHP for the auditory processing of conspecific emotions. For instance, fMRI studies in macaques have revealed a greater involvement of the STG for the perception of conspecific emotional calls compared to heterospecific ones including calls from other primate and animal species, environmental sounds and scrambled vocalizations [START_REF] Joly | Processing of Vocalizations in Humans and Monkeys: A Comparative FMRI Study[END_REF][START_REF] Ortiz-Rios | Functional MRI of the Vocalization-Processing Network in the Macaque Brain[END_REF][START_REF] Petkov | A Voice Region in the Monkey Brain[END_REF]. Following this, positron emission tomography (PET scan) studies have shown the predominant role of the right PT in chimpanzees [START_REF] Taglialatela | Visualizing Vocal Perception in the Chimpanzee Brain[END_REF]) and of the STS in macaques [START_REF] Gil-Da-Costa | Toward an Evolutionary Perspective on Conceptual Representation: Species-Specific Calls Activate Visual and Affective Processing Systems in the Macaque[END_REF]) for the processing of conspecific emotional calls. Additionally, neurobiological findings in macaques and marmosets (Callitrix jacchus) have suggested a greater involvement of the STG and of the primary auditory cortex in the passive listening of emotional conspecific calls comparing to environmental sounds, scrambled or time-reversed vocalizations [START_REF] Belin | Voice Processing in Human and Non-Human Primates[END_REF][START_REF] Ghazanfar | The Auditory Behaviour of Primates: A Neuroethological Perspective[END_REF][START_REF] Poremba | Species-Specific Calls Evoke Asymmetric Activity in the Monkey's Temporal Poles[END_REF]. Despite these results, the question on the specific status of conspecific emotions in NHP remains poorly explored with respect to heterospecific vocalizations. In particular, because of the species-dependent results in humans highlighted above and the phylogenetic proximity across primate species, it seems necessary to include heterospecific stimuli from other NHP to reconstruct the phylogenetic evolution of primate vocal emotion processing [START_REF] Bryant | The Evolution of Human Vocal Emotion[END_REF].

The present study investigated temporal cortex involvement in three female baboons: Talma, Rubis and Chet, during exposure to conspecific vs. heterospecific affective vocalizations, using fNIRS. Building on a growing interest over the past decade [START_REF] Boas | Twenty Years of Functional Near-Infrared Spectroscopy: Introduction for the Special Issue[END_REF][START_REF] Pan | Applications of Functional Near-Infrared Spectroscopy in Fatigue, Sleep Deprivation, and Social Cognition[END_REF], we used fNIRS because of its non-invasiveness, its poor sensitivity to motion artefacts [START_REF] Balardin | Imaging Brain Function with Functional Near-Infrared Spectroscopy in Unconstrained Environments[END_REF]) and its suitability for comparative research [START_REF] Debracque | Validating the Use of Functional Near-Infrared Spectroscopy in Monkeys: The Case of Brain Activation Lateralization in Papio Anubis[END_REF][START_REF] Fuster | Near-Infrared Spectroscopy (NIRS) in Cognitive Neuroscience of the Primate Brain[END_REF][START_REF] Kim | Application of Functional Near-Infrared Spectroscopy to the Study of Brain Function in Humans and Animal Models[END_REF][START_REF] Lee | Prefrontal Cortical Activity Associated with Visual Stimulus Categorization in Non-Human Primates Measured with near-Infrared Spectroscopy[END_REF][START_REF] Wakita | Measurement of Neuronal Activity in a Macaque Monkey in Response to Animate Images Using Near-Infrared Spectroscopy[END_REF]. According to the existing literature on NHP and humans suggesting a sensitivity of the primates' temporal cortex for conspecific calls, we expected i) more activation in the temporal cortex for the passive listening of baboon sounds compared to chimpanzee stimuli; and ii) a greater involvement of the temporal cortex for the perception of agonistic conspecific vocalizations in comparison to the other sounds.

Material & Methods

Subjects

Three healthy female baboons (Talma, Rubis and Chet, mean age = 14.6 years, SD ± 3.5 years) were included in the present study. Based on the annual health assessment and the daily behavioural surveys made by the veterinary and animal welfare staff, the subjects had normal hearing abilities and did not present a structural neurological impairment (confirmed with respective T1w anatomical brain images -0.7 x 0.7 x 0.7 resolution -collected in vivo under anesthesia in the 3Tesla MRI Brunker machine).

All procedures were approved by the "C2EA -71 Ethical Committee of neurosciences" (INT Marseille) and performed in accordance with the relevant French law, CNRS guidelines and the European Union regulations. The subjects were born in captivity and housed in social groups at the Station de Primatologie in which they have free access to both outdoor and indoor areas. All enclosures are enriched by wooden and metallic climbing structures as well as substrate on the group to favour foraging behaviours. Water is available ad libitum and monkey pellets, seeds, fresh fruits and vegetables were given every day. The three subjects were lightly anesthetized with propofol and passively exposed to auditory stimuli as described below (see also [START_REF] Debracque | Validating the Use of Functional Near-Infrared Spectroscopy in Monkeys: The Case of Brain Activation Lateralization in Papio Anubis[END_REF] for the complete protocol).

Stimuli

Auditory stimulations consisted of agonistic vocalizations expressed by baboon (conspecific -see Figure 1a) and chimpanzee (heterospecific -see Figure 1b) species as well as energy matched white noises to control for this low-level acoustic feature and for its unfolding (i.e. the temporal structure of energy of the vocalizations). Each stimulus had a duration of 20 seconds, and was repeated six times (see [START_REF] Debracque | Validating the Use of Functional Near-Infrared Spectroscopy in Monkeys: The Case of Brain Activation Lateralization in Papio Anubis[END_REF] for more details). The auditory stimuli were pseudo-randomized, alternating vocalizations and white noises; and were separated by 15 seconds of silence. Additionally, auditory stimulations were broadcasted either binaurally or monaurally in the right or left ear. chimpanzee vocalizations used as stimuli in the present study. These graphical representations were extracted using the PhonTools package [START_REF] Barreda | phonTools: Tools for Phonetic and Acoustic Analyses [computer program[END_REF] on R. studio (Team 2020).

fNIRS

Recordings

Brain activations were measured using two light and wireless fNIRS devices (Portalite, Artinis Medical Systems B.V., Elst, The Netherlands) enabling the measurement of Oxyhemoglobin (O2Hb). Optical probes were placed on the right and left temporal cortices of the subjects using T1 MRI scanner images previously acquired at the Station de Primatologie on baboons (see Figure 2). Data were obtained at 50 Hz with two wavelengths (760 and 850 nm) using three channels per hemisphere (ch1, ch2, ch3) with three inter-distance probes (3 -3.5 -4 cm) investigating three different cortical depths (1.5 -1.7 -2 cm respectively).

Reducing the potential disturbing impact of the fNIRS protocol on the subjects, each experimental session was planned during the baboons' routine health inspection at the Station de Primatologie. As part of the health check, subjects were isolated from their social group and anesthetized with an intramuscular injection of ketamine (5 mg/kg -Ketamine 1000®) and medetomidine (50µg/kg -Domitor®). Then Sevoflurane (Sevotek®) at 3 to 5% and atipamezole (250 µg/kg -Antisedan®) were administered before recordings. Each baboon was placed in ventral decubitus position on the table and the head of the individual was maintained using foam positioners, cushions and Velcro strips to remain straight and to reduce potential motion occurrences. Vital functions were monitored (SpO2, Respiratory rate, ECG, EtCO2, T°) and a drip of NaCl was put in place during the entire anaesthesia. Before fNIRS recordings, temporal areas on the baboons' scalp were shaved and sevoflurane inhalation was stopped.

Subjects were further sedated with a minimal amount of intravenous injection of Propofol (Propovet®) with a bolus of around 2mg/kg every 10 to 15 minutes or by infusion rate of 0.1 -0.4 mg/kg/min. After the recovery period, subjects were put back in their social group and monitored by the veterinary staff.

Analysis

SPM_fNIRS toolbox [START_REF] Tak | Sensor Space Group Analysis for FNIRS Data[END_REF]) and custom made codes on Matlab 7.4 R2009b (The MathWorks Inc. 2009) were used to perform first level analysis on raw fNIRS data following this procedure: i) O2Hb concentration changes were calculated using the Beer-Lambert law [START_REF] Delpy | Estimation of Optical Pathlength through Tissue from Direct Time of Flight Measurement[END_REF]; ii) motion artifacts were removed manually in each individual and each channel. In total, 10 seconds (1.3%) were removed from the O2Hb signal of Rubis and 35 seconds (4.8%) for Talma and Chet; iii) a low-pass filter based on the HRF [START_REF] Friston | To Smooth or Not to Smooth? Bias and Efficiency in FMRI Time-Series Analysis[END_REF] was applied to reduce physiological confounds; iv) a baseline correction was applied in subtracting the pre-stimulus baseline from the post-stimulus O2Hb concentration changes of each trial and v) O2Hb signal was averaged for Talma in a window of 4 to 12 s post stimulus onset for each trial; and for Rubis and Chet in a window of 2 to 8 s post stimulus onset in order to select the range of maximum O2Hb concentration changes following Debracque et al 2021. Shortly, the differences of concentration range are explained by the presence of tachycardia episodes for both Rubis and Chet during the experiment, involving an HRF almost twice as fast as the one found for Talma.

The second level analysis was made on R. studio (Team 2020) using the permuco package [START_REF] Frossard | Permutation Tests for Regression, ANOVA and Comparison of Signals : The Permuco Package[END_REF]. In each Hemisphere (right, left), we used non-parametric permutation tests with 5000 iterations to assess O2Hb concentration changes for each subject (Talma, Rubis, Chet) as they enable repeated measures ANOVA in small sample sizes by multiplying the design and response variables (Kherad-Pajouh and Renaud 2015). Stimuli (call, white noise); Species (baboon, chimpanzee); Channels (ch1, ch2, ch3) and Sides (right, left, both ears) were selected as fixed factors. As recommended, contrast effects of Species and Stimuli within channels were assessed with 2000 permutations (Kherad-Pajouh and Renaud 2015). Both p. values for permutation F (pperm) and parametric F are reported.

Results

The main effect Channels was significant in nearly all subjects and hemispheres: Talma 2,3) = 25.68 , p | pperm <.001). It was not significant for Rubis' left hemisphere (F(2,3) = 2.15 , p | pperm =.12). Hence, we reported the effects of Species and Stimuli according to channels in Figure 3. Note that for all subjects, the factor Sides did not reach significance and thus, do not statistically explain differences for Stimuli and Species (see [START_REF] Debracque | Validating the Use of Functional Near-Infrared Spectroscopy in Monkeys: The Case of Brain Activation Lateralization in Papio Anubis[END_REF] for more details related to auditory asymmetries). All results are reported in Supplementary Materials.

Regarding the right hemisphere, permutation tests revealed for Chet a significant main effect of the factor Species (F(1,2) = 5.03, p | pperm <.05).

Regarding the left hemisphere, the main factors Species was found significant for the baboon Talma (F(1,2) = 4.24, p| pperm <.05). In addition, a significant two-way interaction was found significant for the subject Chet between Stimuli and Species (F(1,4) = 4,13 , p | pperm =.05).

In sum, across the three channels, more O2Hb concentration changes were found in Talma's left hemisphere for the perception of chimpanzee sounds compared to baboon stimuli. Conversely, for Chet, permutation analyses revealed more O2Hb concentration changes in the right hemisphere for the passive listening of baboon sounds comparing to chimpanzee ones. Additionally, her left hemisphere was more activated by baboon calls vs. chimpanzee calls and by chimpanzee white noises vs. baboon white noises. [START_REF] Wickham | ggplot2: Create Elegant Data Visualisations Using the Grammar of Graphics [computer program[END_REF]) on R.studio [START_REF] Team | RStudio: Integrated Development for R. RStudio[END_REF] was used for visualizing the data.

Discussion

The present fNIRS study suggests, in two out of our three tested baboons, a sensitivity of the baboons' temporal cortex for conspecific sounds with documented differential activations in contrast to heterospecific sounds. This finding is quite consistent with the few existing fMRI data in macaques showing the distinctive role of STG in the perception of emotions in conspecific and heterospecific calls [START_REF] Joly | Processing of Vocalizations in Humans and Monkeys: A Comparative FMRI Study[END_REF][START_REF] Petkov | A Voice Region in the Monkey Brain[END_REF]. Similar to humans [START_REF] Belin | Human Cerebral Response to Animal Affective Vocalizations[END_REF][START_REF] Fritz | Human Behavioural Discrimination of Human, Chimpanzee and Macaque Affective Vocalisations Is Reflected by the Neural Response in the Superior Temporal Sulcus[END_REF], this first result suggests a different involvement of temporal regions in NHP for the processing of emotions in conspecifics and heterospecific primate vocalizations. From an evolutionary perspective, this would be a mechanism inherited from the common ancestor of Homo sapiens and other Catharrini around 40 million years ago [START_REF] Harrison | Catarrhine Origins[END_REF], although it may be earlier if Platyrrhini share this feature too.

Despite the significant main effect Species for two subjects, fNIRS data revealed also inter-individual differences between Talma and Chet. First, we failed to record significant results for Rubis, although this may have been a consequence of her constant tachycardia during the health check and experiment (see [START_REF] Debracque | Validating the Use of Functional Near-Infrared Spectroscopy in Monkeys: The Case of Brain Activation Lateralization in Papio Anubis[END_REF]. Second, the left temporal cortex of Talma was overall more activated for chimpanzee sounds (calls and white noise) than for baboon ones; in contrast, results were reversed in the left temporal cortex of Chet, where statistical analyses highlighted an increase of O2Hb concentration changes in the left temporal cortex for the passive listening of agonistic baboon sounds compared to chimpanzee sounds. In addition, in her right temporal cortex, we documented an increase in O2Hb concentration led by the perception of agonistic baboon call.

Differences between individuals in temporal cortex sensitivity could explain this absence of congruence in our fNIRS data. Xu and colleagues (2019), have in fact, demonstrated in five anaesthetized and awake macaques great individual variabilities in functional connectivity across cortical regions [START_REF] Xu | Interindividual Variability of Functional Connectivity in Awake and Anesthetized Rhesus Macaque Monkeys[END_REF]. Interestingly, the authors compared macaques' fMRI data to human ones and concluded to a similar heterogeneity in functional connectivity across primate species. In the same line, Pernet and colleagues also demonstrated, using fMRI, high inter-individuality differences between human STG and STS for the listening of conspecific emotional voices compared to non-vocal sounds [START_REF] Pernet | The Human Voice Areas: Spatial Organization and Inter-Individual Variability in Temporal and Extra-Temporal Cortices[END_REF]. Hence, as for highly cited human neuroimaging studies [START_REF] Szucs | Sample Size Evolution in Neuroimaging Research: An Evaluation of Highly-Cited Studies (1990-2012) and of Latest Practices (2017-2018) in High-Impact Journals[END_REF], future noninvasive comparative research should include more subjects to take in consideration this inter-individual variability in brain mechanisms. Yet, the necessity to increase NHP subjects to address limits in statistical power faces ethical aspects related to animal welfare in the case of invasive neuroimaging studies. The development of fNIRS [START_REF] Debracque | Validating the Use of Functional Near-Infrared Spectroscopy in Monkeys: The Case of Brain Activation Lateralization in Papio Anubis[END_REF] and longitudinal studies in comparative neuroscience [START_REF] Song | Strengths and Challenges of Longitudinal Non-Human Primate Neuroimaging[END_REF]) would thus allow answering parts of these challenges.

Often explored using fMRI or Pet scan (e.g. [START_REF] Bodin | Functionally Homologous Representation of Vocalizations in the Auditory Cortex of Humans and Macaques[END_REF][START_REF] Gil-Da-Costa | Toward an Evolutionary Perspective on Conceptual Representation: Species-Specific Calls Activate Visual and Affective Processing Systems in the Macaque[END_REF][START_REF] Ortiz-Rios | Functional MRI of the Vocalization-Processing Network in the Macaque Brain[END_REF], our fNIRS data remain inconclusive regarding any differences in temporal cortex activity between the passive listening of agonistic baboon vocalizations and white noises. Indeed, comparative research on macaques and marmoset (Callithrix jacchus) showed a greater sensitivity of the temporal cortex in its anterior part than in its posterior area for the contrast conspecific calls vs. control sounds [START_REF] Bodin | Functionally Homologous Representation of Vocalizations in the Auditory Cortex of Humans and Macaques[END_REF]. Future fNIRS studies should improve the probe location on the scalp of baboons or any other NHP species.

Finally, out of the scope of this paper, permutation tests and descriptive analyses highlighted consistent fNIRS data for the channels 1 and 2 compared to channel 3 on both, right and left hemispheres. This result suggests that, for fNIRS in baboons, the best inter-probe distant to assess cortical activations would be between 3cm and 3.5cm. Interestingly, these distances are commonly used for fNIRS experiments in human adults [START_REF] Ferrari | A Brief Review on the History of Human Functional Near-Infrared Spectroscopy (FNIRS) Development and Fields of Application[END_REF].

Overall, highlighting the evolutionary continuity between humans and NHP, our results suggest the existence in baboons of differences in temporal cortex activity between the processing of conspecific and heterospecific sounds. Yet, fNIRS data also pointed out high inter-individual variability in these results and remain inconclusive in regards to the contrast conspecific agonistic vocalizations vs. white noises (control sounds), which are often explored meaningfully using fMRI or Pet scan (e.g. [START_REF] Bodin | Functionally Homologous Representation of Vocalizations in the Auditory Cortex of Humans and Macaques[END_REF][START_REF] Gil-Da-Costa | Toward an Evolutionary Perspective on Conceptual Representation: Species-Specific Calls Activate Visual and Affective Processing Systems in the Macaque[END_REF][START_REF] Ortiz-Rios | Functional MRI of the Vocalization-Processing Network in the Macaque Brain[END_REF]. Moreover, the present study has some limitations. Firstly, our experiment focused on baboons and it is unclear whether it will replicate in other monkey species. In fact, [START_REF] Fitch | Primate Laterality and the Biology and Evolution of Human Handedness: A Review and Synthesis[END_REF] have already suggested differences between monkey in terms of mechanisms for the processing of conspecific and heterospecific vocalizations [START_REF] Fitch | Primate Laterality and the Biology and Evolution of Human Handedness: A Review and Synthesis[END_REF]. Finally, only agonistic vocalizations were included in the present fNIRS protocol. Yet, similar to humans, NHP might have some distinctive brain mechanisms for negative and positive emotions (e.g. [START_REF] Davidson | Anterior Cerebral Asymmetry and the Nature of Emotion[END_REF][START_REF] Frühholz | Multiple Subregions in Superior Temporal Cortex Are Differentially Sensitive to Vocal Expressions: A Quantitative Meta-Analysis[END_REF]Zhang et al. 2018).

Consequently, future studies should consider the inclusion of positive emotions, more individuals or the use of fNIRS and longitudinal studies, as well as various monkey species in order to maximize the generalization of their neuroimaging data on auditory processing of emotions in NHP.

as the French grant "Agence Nationale de la Recherche" (ANR-16-CONV-0002, ILCB to AM) and the Excellence Initiative of Aix-Marseille University (A*MIDEX to AM). TG was additionally supported by a grant of the SNSF during the final re-writing of this article (grant PCEFP1_186832).

Figure 1 :

 1 Figure 1: Representative waveforms and spectrograms of 20s-long agonistic a) baboon and b)

Figure 2 :

 2 Figure 2: fNIRS optode and channel locations according to 89 baboons T1 MRI template (Love et al. 2016). Blue and green crosses represent optical receivers and transmitters respectively. Ch1, Ch2 and Ch3 indicate the three channels on the right and left temporal cortex.

  (right: F(2,3) = 161 ,5 , p | pperm <.001; left: F(2,3) = 33.91 , p | pperm <.001); Rubis (right: F(2,3) = 8, 99 , p | pperm <.001); and Chet (right: F(2,3) = 3,99 , p | pperm <.05; left: F(

Figure 3 :

 3 Figure 3: Right and left temporal cortex activations for the baboons a) Talma, b) Chet and c) Rubis during the perception of agonistic baboon (conspecific) and chimpanzee (heterospecific) vocalizations as well as their energy matched white noises. The mean concentration changes of O2Hb (y axis) is represented in micro molar (µM) for each fNIRS channel (x axis). Colourful dots and dark lines represent stimuli and confidence intervals respectively. Results of the permutation tests within channels are shown with * p<.05; p=.07. The ggplot2 package[START_REF] Wickham | ggplot2: Create Elegant Data Visualisations Using the Grammar of Graphics [computer program[END_REF]) on R.studio[START_REF] Team | RStudio: Integrated Development for R. RStudio[END_REF]

Acknowledgements

We thank the Swiss National Foundation and the European Research Council for funding this work.

We warmly thank the vet Pascaline Boitelle, the animal care staff as well as Jeanne Caron-Guyon, Lola Rivoal, Théophane Piette and Jérémy Roche for assistance during the recordings. CD also thanks Dr.

Ben Meuleman for his wise advices on permutation test analyses.

Funding

This work was supported by the Swiss National Science Foundation (SNSF, grant P1GEP1_181492 to CD), the European Research Council (grant 716931 -GESTIMAGE -ERC-2016-STG to AM) as well (which was not certified by peer review) is the author/funder. All rights reserved. No reuse allowed without permission.

Availability of data and material

Raw data are freely available to any researcher.

Code availability

Custom Matlab and R. studio codes are available on request.

Declarations

Conflict of interest

The authors have no conflicts of interest to declare that are relevant to the content of this article.

Ethics approval

All animal procedures were approved by the "C2EA -71 Ethical Committee of neurosciences" (INT Marseille) under the application number APAFIS#13553-201802151547729, and were conducted at the Station de Primatologie CNRS (UPS 846, Rousset-Sur-Arc, France) within the agreement number C130877 for conducting experiments on vertebrate animals. All methods were performed in accordance with the relevant French law, CNRS guidelines and the European Union regulations (Directive 2010/63/EU).

Consent to participate

Not applicable.

Consent for publication

Not applicable.