What separates us from other primates?

The psychologists behind a new MRI study say it is key components in the ventrolateral frontal cortex area of the human brain, and how these components were connected up with other brain areas. When compared to equivalent MRI data from 25 macaque monkeys, the authors determined that it is unlike anything in the brains of some of our closest evolutionary relatives. 

The ventrolateral frontal cortex area of the brain is involved in many of the highest aspects of cognition and language, and is only present in humans and other primates. Some parts are implicated in psychiatric conditions like ADHD, drug addiction or compulsive behavior disorders. Language is affected when other parts are damaged after stroke or neurodegenerative disease. A better understanding of the neural connections and networks involved should help the understanding of changes in the brain that go along with these conditions. 

"We tend to think that being able to plan into the future, be flexible in our approach and learn from others are things that are particularly impressive about humans. We've identified an area of the brain that appears to be uniquely human and is likely to have something to do with these cognitive powers," says senior researcher Professor Matthew Rushworth of Oxford University's Department of Experimental Psychology.The brain is a mosaic of interlinked areas. We wanted to look at this very important region of the frontal part of the brain and see how many tiles there are and where they are placed. 

"We also looked at the connections of each tile – how they are wired up to the rest of the brain – as it is these connections that determine the information that can reach that component part and the influence that part can have on other brain regions."

From the MRI data, the researchers were able to divide the human ventrolateral frontal cortex into 12 areas that were consistent across all the individuals.

"Each of these 12 areas has its own pattern of connections with the rest of the brain, a sort of "neural fingerprint", telling us it is doing something unique," says Professor Rushworth.

The researchers were then able to compare the 12 areas in the human brain region with the organization of the monkey prefrontal cortex. Overall, they were very similar with 11 of the 12 areas being found in both species and being connected up to other brain areas in very similar ways.

However, one area of the human ventrolateral frontal cortex had no equivalent in the macaque – an area called the lateral frontal pole prefrontal cortex.

"We have established an area in human frontal cortex which does not seem to have an equivalent in the monkey at all,' says first author Franz-Xaver Neubert of Oxford University. 'This area has been identified with strategic planning and decision making as well as "multi-tasking"."

The Oxford research group also found that the auditory parts of the brain were very well connected with the human prefrontal cortex, but much less so in the macaque. The researchers suggest this may be critical for our ability to understand and generate speech.

Published in Neuron. Source: University of Oxford