Primitive Brain Areas as Important as Frontal Lobe for Human Intelligence

Human intelligence cannot be explained by the size of the brain's frontal lobes, which are known for advanced thinking. Instead, researchers have found that more primitive brain areas may explain the intellect of humans.

The frontal lobe in humans has long been believed to be the source of our superior intelligence. It's positioned at the front of the brain, and contains most of the dopamine-sensitive neurons in the cerebral cortex. The dopamine system itself is actually associated with reward, attention, short-term memory tasks, planning and motivation. The frontal lobe is also involved with the ability to recognize future consequences and the ability to choose between good and bad actions. In fact, researchers believe that its expansion eventually allowed us to evolve into the modern humans of today.

"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 makes us human," said lead author, Robert Barton, in a news release. "Probably the most widespread assumption about how the human brain evolved is that size increase was concentrated in the front lobes."

In this latest study, researchers examined the comparative size of the front lobes in humans and other species. They found that, surprisingly, the frontal lobes of humans are not disproportionately enlarged to other areas of the brain. In fact, the size of our front lobes cannot solely account for humans' superior cognitive abilities.

So what can account for our cognitive abilities? The researchers suggested that more "primitive" areas, such as the cerebellum, may have been equally important in the expansion of the human brain.

"This means that areas traditionally considered to be more primitive were just as important during our evolution," said Barton in a news release. "These other areas should now get more attention. In fact, there is already some evidence that damage to the cerebellum, for example, is a factor in disorders such as autism and dyslexia."

In fact, it's very possible that our high-level abilities are carried out by more extensive brain networks linking many different areas of the brain-including the "primitive" ones. It could be the structure of these extended networks more than the size of any isolated brain region that is critical for cognitive functioning. These findings have important implications for the study of disorders such as autism.

The study is published in the journal Proceedings of the National Academy of Sciences.