A new study published today found new connections in the human brain

Neuroscientists now know more about how our language-ready brains developed over time. Compared to chimpanzee brains, the way our language areas are connected has changed more than was thought before. Researchers from Radboud University and the University of Oxford publish their findings in PNAS today.

“At first glance,” according to co-first author Joanna Sierpowska, “the brains of humans and chimpanzees look very much alike. The perplexing difference between them and us is that we humans communicate using language, whereas non-human primates do not.”  Researchers have been trying for years to figure out what in the brain might have made this unique ability possible.

However, up until this point, their focus has primarily been on the arcuate fasciculus, a particular nerve tract that connects the frontal and temporal lobes and is known to play a role in language function in addition to revealing important variances between species.

The interconnectedness of two temporal lobe cortical areas, which are equally crucial for language usage, is the new topic of emphasis, adds Sierpowska.

Detection of white matter

To explore the differences between the human and chimpanzee brains, researchers scanned 50 human brains and 29 chimpanzee brains in a manner similar to humans, but under well-controlled anesthesia and as part of their routine veterinary exams.

In particular, they used a method called diffusion-weighted imaging (DWI), which takes pictures of white matter, which is made up of nerve pathways that link different parts of the brain.

These images were used to examine and compare the connectivity of two language-related brain hubs (the anterior and posterior middle portions of the temporal lobe). “In humans, both of these areas are considered crucial for learning, using and understanding language and harbor numerous white matter pathways,” adds Sierpowska. 

“It is also known that damage to these brain areas has detrimental consequences for language function. However, until now, the question of whether their pattern of connections is unique to humans remained unanswered.”

New neural connections in the human brain

While the connectivity of the posterior middle temporal areas in chimps is primarily limited to the temporal lobe, the researchers discovered that in humans, a new connection towards the frontal and parietal lobes evolved via the arcuate fasciculus as an anatomical avenue.

In fact, the temporal lobes’ connection has expanded as a result of modifications to both human language areas.

The findings of the study show “that the arcuate fasciculus surely is not the only driver of evolutionary changes preparing the brain for a full-fledged language capacity”, adds co-author Vitoria Piai.

According to Piai, these “findings are purely anatomical, so it is hard to say anything about brain function in this context”.

The fact that this network of connections is so unique to humans, however, implies that it may be a critical part of brain organization that enables our unique language talents.

Image Credit: Getty

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