Search

The planum temporale (PT), a key language area, is specialized in the left hemisphere in prelinguistic infants and considered as a marker of the pre-wired language-ready brain. However, studies have reported a similar structural PT left-asymmetry not only in various adult non-human primates, but also in newborn baboons. Its shared functional links with language are not fully understood. Here we demonstrate using previously obtained MRI data that early detection of PT left-asymmetry among 27 newborn baboons (Papio anubis, age range of 4 days to 2 months) predicts the future development of right-hand preference for communicative gestures but not for non-communicative actions. Specifically, only newborns with a larger left-than-right PT were more likely to develop a right-handed communication once juvenile, a contralateral brain-gesture link which is maintained in a group of 70 mature baboons. This finding suggests that early PT asymmetry may be a common inherited prewiring of the primate brain for the ontogeny of ancient lateralised properties shared between monkey gesture and human language.The planum temporale is a key structure in the human language network. Here the authors show that planum temporale asymmetry at birth in baboons predicts the development of communicative right-hand use, which suggests some common features in the wiring of communicative properties between species. [ABSTRACT FROM AUTHOR]

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 brain's readiness for language acquisition. Nevertheless, this latter interpretation was questioned by a recent report in non-human 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 remains unclear but critical to investigate potential continuities of cortical specialization with human infants. Here we report a population-level leftward asymmetry of the PT grey matter volume in in vivo 34 newborn baboons P. anubis, which showed intra-individual positive correlation with PT surface's 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. [ABSTRACT FROM AUTHOR]