Scientists challenge a 70-year-old “lizard brain” myth

The prevailing notion that the human brain consists of a rational "logical brain" and an instinctual "lizard brain" has been challenged by recent research. This simplistic view fails to capture the complex evolutionary history of our brain. Assistant Professor Nabil Imam, from Georgia Tech's Institute for Neuroscience, Neurotechnology, and Society, explains that the brain's development is more intricate than a straightforward struggle between old and new structures.

Contrary to popular belief, brain regions like the neocortex, associated with higher-level thought, and the limbic system, linked to emotions, are not just stacked on top of one another. Instead, they are interconnected networks that expand and contract together over evolutionary time. Imam and his colleagues found that when one limbic system region becomes larger, the other limbic regions also tend to grow, while the neocortex generally remains smaller. This coordinated expansion suggests that these brain regions work together as an integrated unit.

The researchers used AI models to explore why the size of these brain systems changes consistently among species. They discovered that the brain has limited resources, such as space and energy, and that natural selection may favor whichever wiring system is most useful for survival in a particular environment. For example, species heavily reliant on smell, like the nine-banded armadillo, have a much larger limbic system, while those like the squirrel monkey, which rely on vision, have brains dominated by the neocortex.

These findings could help explain why our brain appears to balance sophisticated reasoning with basic instincts. Moreover, understanding this brain organization could lead to the development of AI systems that learn more like biological brains, requiring less data and energy. The researchers suggest that by translating this "nature" architecture into artificial intelligence, we could create systems that mimic the brain's efficient use of resources.