Ontogeny of gesture & brain lateralization in baboons: A developmental model of hemispheric specialization for language? – BABONTO

Human language is an unique communicative system involving mostly the left hemisphere of the brain. Such a lateralization is visible at the structural level, even at birth, in key cortical language areas, such as the perisylvian Planum Temporale (PT) and its main connecting fiber tract with Broca’s area - the arcuate fasciculus (AF). To address the question of its origins, the studies of the communicative gestural system of our primate cousins, including our own research in baboons, have showed similar key intentional and referential properties of language as well as some similar underlying left structural hemispheric specialization. While our previous MRI brain imaging studies in baboons Papio anubis reported human-like left PT structural asymmetry in both adults and newborns, we also found that their handedness for communicative gesturing – but not for manipulation – was related to contralateral brain asymmetry of a marker of Broca’s homolog, suggesting that those brain asymmetries were not human- or language-specific but associated to gestures in monkeys. Within this evolutionary framework on the gestural origin of language lateralization, the respective ontogeny of those brain/behaviors specialization for communication and their potential causal links are unknow in both human and nonhuman primates. In order to address those unexplored questions, the present project will take advantage on previous anatomical and diffusion brain MRI images collected at 4 time points from birth to adolescence in 30 growing baboons. We have an unique opportunity and time-frame window to keep following longitudinally until adulthood the development of behaviors of this cohort living in social groups. We aim thus at investigating the ontogeny of gestural and brain lateralization for language homolog structures (Broca, PT) and their white mater tract (AF), as well as their potential causal relationship, from birth to advanced adulthood, covering thus the first 10 years of life span.