Biology subjects

Meguerditchian, A.

Publications and source records attributed to Meguerditchian, A..

9 recordsLinked to original sources

bioRxiv2025

Light propofol anaesthesia for non-invasive auditory EEG recording in unrestrained non-human primates.

Non-invasive electroencephalographic (EEG) experiments have been instrumental in advancing our understanding of the brain mechanisms involved in the production and perception of sounds and human speech. Performing similar experiments in non-human primates (NHPs) would help further deepen our knowledge by allowing us to investigate the evolutionary roots of these processes. However, performing EEG on NHPs is a challenge, given its sensitivity to motion artefacts, device cost and durability, and animal training requirements. For these reasons, most attempts have used invasive intracranial recordings, which led us to develop an alternative that minimises stress and prioritises animal welfare. By using mild propofol sedation, neurophysiological experimentation can easily be integrated into the routine sanitary checks of captive animals and allows the optimisation of both EEG quality and animal welfare. To assess the influence of propofol on brain activity in NHPs, we sedated three olive baboons (Papio anubis), scored their sleep stages under different doses, and recorded auditory event-related potentials (ERP)in response to grunts. Analyses of the EEG recordings with regards to sleep stage and ERP components indicate that at low dose (< 0.1mg/kg/h), propofol induces a light sleep state conducive to recording stimulus-elicited auditory activity. Overall, this experiment confirms the use of propofol sedation as an appropriate technique to study auditory processes through unrestrained, non-invasive EEG in NHPs.

neuroscience↗

bioRxiv2022

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

Are conspecific emotional vocalizations special? Although often investigated in non-human primates using functional magnetic resonance imaging or positron emission tomography, it remains unclear whether the listening of conspecific vocal emotions leads to similar or different cerebral activations when compared to heterospecific calls (i.e. expressed by another primate species). Using a neuroimaging technique rarely employed in monkeys so far, functional Near Infrared Spectroscopy (fNIRS), the present study investigated cortical temporal activities during exposure to both conspecific and heterospecific calls in three female adult baboons (Papio anubis). The three subjects were lightly anesthetized and passively exposed to agonistic baboon and chimpanzee (Pan troglodytes) vocalizations, as well as energy matched white noises in order to control for this low-level acoustic feature. Despite inter-individual variabilities, permutation test analyses on the extracted OxyHemoglobin signal revealed for two subjects out of three significant differences between the passive listening of baboon versus chimpanzee stimuli. Additionally, in one subject, a modulation of the left temporal cortex activity was found for the perception of baboon calls contrasted to chimpanzee vocalizations as well as for the passive listening of baboon white noises compared to chimpanzee ones. Although the lack of generalization of those findings in all three subjects prevents us to drawn any conclusion and that more subjects would be needed, the hypothesis that baboons cortical temporal regions may be more sensitive to the processing of conspecific sounds compared to heterospecific stimuli is not excluded. Our study highlights that fNIRS may be a promising alternative to further investigate the auditory mechanisms at play in the right and left baboons temporal cortices for the processing of emotional vocalizations.

neuroscience↗

bioRxiv2021

Age- and sex-related differences in baboon (Papio anubis) gray matter covariation

Age-related changes in cognition, brain morphology, and behavior are exhibited in several primate species. Baboons, like humans, naturally develop Alzheimers disease-like pathology and cognitive declines with age and are an underutilized model for studies of aging. To determine age-related differences in gray matter covariation of 89 olive baboons (Papio anubis), we used source-based morphometry (SBM) to analyze data from magnetic resonance images. We hypothesized that we would find significant age effects in one or more SBM components, particularly those which include regions influenced by age in humans and other nonhuman primates (NHPs). A multivariate analysis of variance revealed that individual weighted gray matter covariation scores differed across the age classes. Elderly baboons contributed significantly less to gray matter covariation components including the brainstem, superior parietal cortex, thalamus, and pallidum compared to juveniles, and middle and superior frontal cortex compared to juveniles and young adults (p<0.05). Future studies should examine the relationship between the changes in gray matter covariation reported here and age-related cognitive decline.

neuroscience↗

bioRxiv2021

Maternal cradling bias drives early handedness in infant monkeys: A longitudinal study of grasping lateralization in baboons

The most emblematic behavioral manifestation of human brain asymmetries is handedness. While the precise mechanisms behind the development of handedness are still widely debated, empirical evidences highlight that besides genetic factors, environmental factors may play a crucial role. As one of these factors, maternal cradling behavior may play a key role in the emergence of early handedness in the offspring. In the present study we followed 41 olive baboon (Papio anubis) infants living in different social groups with their mother for which direction (e.g., left- or right-arm) and degree of maternal cradling-side bias were available from our previous published study. We assessed hand preferences for an unimanual grasping task at 3 developmental stages: (1) 0-4, (2) 4-6 and (3) 9-10 months of age. We found that individual hand preferences for grasping exist as soon as the first months of age, with a population-level left-handedness predominance, being stable until 6 months; to wit the period during which juveniles are mainly carried by their mothers. More importantly, this early postnatal handedness is positively correlated with maternal cradling lateralization. Interestingly, hand preferences assessed later in the development, once juveniles are no longer carried (i.e., from 9 to 10 months of age), are less consistent with the earlier developmental stages and no longer dependent from the maternal cradling bias. Our findings suggest that the ontogenetic dynamics of the infants hand preference and its changes might ultimately rely on the degree of infant dependence from the mother across development. Research HighlightsO_LIEarly postnatal individual hand preferences are detected for unimanual food grasping within the first four months of age. C_LIO_LIEarliest measures of infant hand preference are positively correlated with measures of maternal cradling lateralization. C_LIO_LIHand preferences assessed later in the development, from 9 to 10 months of age are less consistent with the earlier developmental stages and independent from maternal cradling bias. C_LI

animal behavior and cognition↗

bioRxiv2021

Planum Temporale grey matter volume asymmetries in new-born monkeys (Papio anubis)

The Planum Temporale (PT) is one of the key hubs of the language network in the human brain. The gross asymmetry of this perisylvian region toward the left brain was considered as the most emblematic marker of hemispheric specialization of language processes in the brain. Interestingly, this neuroanatomical signature was documented also in newborn infants and preterms, suggesting the early brains readiness for language acquisition. Nevertheless, this latter interpretation was questioned by a recent report in nonhuman primates of a potential similar signature in newborn baboons Papio anubis based on PT surface measures. Whether this "tip of the iceberg" PT asymmetry is actually reflecting asymmetry of its underlying grey matter volume remain unclear but critical to investigate potential continuities of cortical specialization with human infants. Here we report a population-level leftward asymmetry of the Planum Temporale grey matter volume in in vivo 34 newborn baboons Papio anubis, which showed intra-individual positive correlation with PT surfaces asymmetry measures but also a more pronounced degree of leftward asymmetry at the population-level. This finding demonstrates that PT leftward structural asymmetry in this Old World monkey species is a robust phenomenon in early primate development, which clearly speaks for a continuity with early human brain specialization. Results also strengthen the hypothesis that early PT asymmetry might be not a human-specific marker for the pre-wired language-ready brain in infants.

neuroscience↗

bioRxiv2021

On the Gestural Origin of Language Lateralisation: Manual Communication reflects Broca's Asymmetry in Monkeys

Manual gestures and speech recruit a common neural network, involving Brocas area in the left hemisphere. Such speech-gesture integration gave rise to theories on the critical role of manual gesturing in the origin of language. Within this evolutionary framework, research on gestural communication in our closer primate relatives has received renewed attention for investigating its potential language-like features. Here, using in-vivo anatomical MRI in 50 baboons, we found that communicative gesturing is related to Broca homologues marker in monkeys, namely the ventral portion of the Inferior Arcuate sulcus (IA sulcus). In fact, both direction and degree of gestural communications handedness - but not handedness for object manipulation - are associated and correlated with contralateral depth asymmetry at this exact IA sulcus portion. In other words, baboons that prefer to communicate with their right hand have a deeper left-than-right IA sulcus, than those preferring to communicate with their left hand and vice versa. Interestingly, in contrast to handedness for object manipulation, gestural communications lateralisation is not associated to the Central sulcus depth asymmetry, suggesting a double dissociation of handedness types between manipulative action and gestural communication. It is thus not excluded that this specific gestural lateralisation signature within the baboons frontal cortex might reflect a phylogenetical continuity with language-related Broca lateralisation in humans.

neuroscience↗

bioRxiv2020

Corpus callosum morphology across the lifespan in baboons (Papio anubis): a cross-sectional study of relative mid-sagittal surface area and thickness

The axons forming the corpus callosum enable integration and coordination of cognitive processing between the cerebral hemispheres. In the aging human brain, these functions are affected by progressive axon and myelin deteriorations, which results in a substantial atrophy of the midsagittal corpus callosum in old age. In non-human primates, these degenerative processes are less pronounced as previous morphometric studies on capuchin monkey, rhesus monkeys, and chimpanzees do not find old-age callosal atrophy. The objective of the present study was to extend these previous findings by studying the aging trajectory of the corpus callosum of the olive baboon (Papio anubis) across the lifespan. For this purpose, total relative (to forebrain volume) midsagittal area, subsectional area, and regional thickness of the corpus callosum was assessed in 91 male and female animals using non-invasive MRI-based morphometry. The studied age range was 2.5 to 26.6 years, and the sample included 11 old-age animals (above the age of 20 years). Fitting lifespan trajectories using general additive modelling (GAM) we found that the relative area of the total corpus callosum and the anterior subsection follow a positive linear trajectory. That is, both measures increased slowly but continuously from childhood into old age, and no stagnation of growth or decline was observed in old age. Thus, comparable with all other non-human primates studied to-date, baboons do not show callosal atrophy in old age. This observation lends supports to the notion that atrophy of the corpus callosum is a unique characteristic of human brain aging.

neuroscience↗

bioRxiv2020

Brain activation lateralization in monkeys (Papio Anubis) following asymmetric motor and auditory stimulations through functional Near Infrared Spectroscopy

Hemispheric asymmetries have long been seen as characterizing the human brain; yet, an increasing number of reports suggest the presence of such brain asymmetries in our closest primate relatives. However, most available data in non-human primates have so far been acquired as part of neurostructural approaches such as MRI, while comparative data in humans are often dynamically acquired as part of neurofunctional studies. In the present exploratory study in baboons (Papio Anubis), we tested whether brain lateralization could be recorded non-invasively using a functional Near-Infrared Spectroscopy (fNIRS) device in two contexts: motor and auditory passive stimulations. Under light propofol anaesthesia monitoring, three adult female baboons were exposed to a series of (1) left-versus right-arm passive movement stimulations; and (2) left-versus right-ear versus stereo auditory stimulations while recording fNIRS signals in the related brain areas (i.e., motor central sulcus and superior temporal cortices respectively). For the motor condition our results show that left-arm versus right-arm stimulations induced typical contralateral difference in hemispheric activation asymmetries in the three subjects for all three channels. For the auditory condition, we also revealed typical human-like patterns of hemispheric asymmetries in one subject for all three channels, namely (1) typical contralateral differences in hemispheric asymmetry between left-ear versus right-ear stimulations, and (2) a rightward asymmetry for stereo stimulations. Overall, our findings support the use of fNIRS to investigate brain processing in non-human primates from a functional perspective, opening the way for the development of non-invasive procedures in non-human primate brain research.

neuroscience↗

bioRxiv2019

Sulcal organization in the medial frontal cortex reveals insights into primate brain evolution

Although the relative expansion of the frontal cortex in primate evolution is generally accepted, the nature of the human uniqueness, if any, and between-species anatomo-functional comparisons of the frontal areas remain controversial. To provide a novel interpretation of the evolution of primate brains, sulcal morphological variability of the medial frontal cortex was assessed in old-world monkeys (macaque, baboon) and Hominoidea (chimpanzee, human). We discovered that both Hominoidea do possess a paracingulate sulcus, which was previously thought to be uniquely human and linked to higher cognitive functions like mentalizing. Also, we revealed systematic sulcal morphological organisations of the medial frontal cortex that can be traced from multiple old-world monkey to Hominoidea species, demonstrating an evolutionary conserved organizational principle. Our data provide a new framework to compare sulcal morphology, cytoarchitectonic areal distribution, connectivity, and function across the primate order, leading to clear predictions on how other primate brains might be anatomo-functionally organized.

neuroscience↗