Baboons’ Brain Anatomy Predicts Hand Preference for Communication

Summary: A study on newborn baby baboons’ brain anatomy predicts their future hand preference for communication. Researchers found that baboons with left-side brain asymmetry in the planum temporale (PT) tend to use their right hand for gestures.

This discovery suggests a shared evolutionary trait between baboons and humans, dating back 25 million years. These findings could aid in clinical applications, such as determining language dominance before brain surgery.

Key Facts:

  1. Baboons with left-side PT asymmetry prefer right-hand gestures for communication.
  2. PT asymmetry in baboons mirrors that in humans, indicating a shared evolutionary trait.
  3. This research could help identify the dominant language hemisphere in brain surgery patients.

Source: CNRS

By studying the brain anatomy of newborn baby baboons, a research group including several CNRS scientists was able to predict what hand they would use to communicate after they had been weaned.

These researchers had already found that nearly 70% of newborn baboons, like human babies, had early asymmetry in the planum temporale (PT) area of the brain. The PT, which is also a key area for language in humans, was larger in the left brain hemisphere than in the right in this group of baby baboons.

This shows a baboon.
This study casts a new light on the links between gesture and language in the evolution of primates by demonstrating their cerebral prewiring. Credit: Neuroscience News

In the new study, which will be published in Nature Communications on the 5 June 2024, the scientists found that as these baboons grew up, they tended to develop a right-hand preference for gestural communication.

This tendency was independent of their right- or left-handedness for other, non-communicative actions such as manipulating objects to extract food. In contrast, the remaining 30% of young baboons – those who were showing no brain asymmetry for the PT or an asymmetry toward the right when newborn – had an equal likelihood of later communicating preferentially with their left or right hand.

This discovery implies that PT asymmetry is not just a neuroanatomical requirement for language development in humans but also one for the development of gestural communication in monkeys, suggesting a shared evolutionary heritage which could date back to their common ancestor 25 million years old.

The scientists based their conclusions on behavioral observations that they made on a group of young baboons previously examined for early brain asymmetry based on MRI images obtained at birth.

In this work, they identified the hand that the baboons preferentially used to make the most common gestures of their communication repertoire, namely rubbing or slapping a hand on the ground to threaten other baboons.

This study casts a new light on the links between gesture and language in the evolution of primates by demonstrating their cerebral prewiring.  This “gestural” path could have promising clinical implications for brain surgery patients, notably to determine the dominant hemisphere for language based on simple communicative gestures’ measurements, to minimize risks of post-operative aphasia.

About this evolutionary neuroscience research news

Author: Manon Landurant
Source: CNRS
Contact: Manon Landurant – CNRS
Image: The image is credited to Neuroscience News

Original Research: Open access.
Planum Temporale asymmetry in newborn monkeys predicts the future development of gestural communication’s handedness” by Adrien Meguerditchian et al. Nature Communications


Abstract

Planum Temporale asymmetry in newborn monkeys predicts the future development of gestural communication’s handedness

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.

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