The frontal lobes are not disproportionately larger compared to other regions of the brain, suggesting other areas of the brain may play a role in humans’ unique cognitive abilities, according to new research published Monday in the Proceedings of the National Academy of Sciences
Researchers from Durham University and Reading University compared the size of the frontal lobes – regions of a mammal’s brain that are located at the front of each cerebral hemisphere – in both people and other animal species in what they are calling “the most accurate and conclusive study of this area of the brain” to date.
They discovered it is not large enough to be solely responsible for our species’ intelligence, and that other areas of the brain (such as the cerebellum) also played a role in the expansion of human intelligence
. Furthermore, the study authors assert these other regions could play surprisingly important roles, not just in cognitive ability but also in related medical disorders such as autism and dyslexia.
“Probably the most widespread assumption about how the human brain evolved is that size increase was concentrated in the frontal lobes,” lead author Professor Robert Barton
of the Durham University Department of Anthropology, said in a statement.
“It has been thought that frontal lobe expansion was particularly crucial to the development of modern human behavior, thought and language, and that it is our bulging frontal lobes that truly make us human. We show that this is untrue: human frontal lobes are exactly the size expected for a non-human brain scaled up to human size,” he added. “This means that areas traditionally considered to be more primitive were just as important during our evolution.”
Those other areas, Barton said, should start receiving more attention from scientists, as there is already some evidence linking damage to the cerebellum with autism and dyslexia.
Furthermore, he and his colleagues believe several of an individual’s most complex abilities are carried out using extensive neurological networks that link several different parts of the brain. They report the structure of those networks – not the size of any one specific brain region – is likely what is most essential in cognitive function.
Past research had attempted to determine whether or not a human’s frontal lobes are disproportionately larger compared to their size in apes, monkeys and other primates. However, Barton’s team said the results of those studies have been largely inconsistent due to the their methods and measurements.
The UK researchers looked at data sets from previous human and animal studies using phylogenetic methods. These methods, which focus on studying evolutionary relationships between organisms, produced results that were consistent throughout all of their data.
They said they used a new method which looked at the speed with which evolutionary changes occurred, and found the frontal lobes did not evolve particularly fast in the human line once it split from the chimpanzee lineage. Their research was funded by the Leverhulme Trust, which distributes grants for educational and research purposes.