Connections between brain regions unique to humans provide speech function

(ORDO NEWS) — Scientists have compared the brains of humans and chimpanzees and have identified new connections, unique to humans, between language areas of the brain that were previously unknown. The discovery gives a more complete picture of which structures of our brain provide speech function.

At first glance, the human brain is very similar to the brain of its closest relative, the chimpanzee. However, unlike all other primates, we communicate through speech. The question of what structures and mechanisms of the brain provide people with a unique speech function has occupied researchers for many years.

Until now, the attention of scientists has been attracted mainly by the arcuate bundle – the nerve tract connecting the frontal and temporal lobes of the brain. It varies greatly between humans and related primates, and is also known to be involved in speech function.

Now scientists from the University of Nijmegen (Netherlands) and the University of Oxford (UK) have decided to shift their attention to the connection between the two language areas of the cerebral cortex located in the temporal lobe.

The authors of the work scanned the brains of 50 people and 29 chimpanzees. In particular, they used diffusion-weighted magnetic resonance imaging (DW-MRI), which allows visualization of the white matter and nerve pathways connecting brain regions.

Using these images, the scientists examined the relationship between the anterior and posterior midtemporal lobe and compared it across the two species. In humans, both of these sites are considered critical for language learning, use, and comprehension, and contain numerous white matter pathways.

It is also known that damage to these areas of the brain can seriously impair speech function. However, until now, the question of whether their wiring diagram is unique to humans has remained open.

Now scientists have shown that the connections between regions of the human brain were much more developed than in chimpanzees.

In addition, the connection of the posterior temporal regions in chimpanzees is limited mainly to the temporal lobe, in humans there is also a new connection with the frontal and parietal lobes, using the arcuate fasciculus as an anatomical pathway.

This architecture is unique to humans and may be the crucial aspect of brain organization that has enabled our language abilities.

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