Understanding the Formation of Brain Cortex Folds in Humans and Animals

The human brain's unique ability to facilitate language, complex thought, memory, and creativity is partly due to the highly folded structure of the cerebral cortex. These folds, consisting of grooves (sulci) and ridges (gyri), not only expand the surface area of the brain but also play a critical role in higher cognitive functions. Interestingly, while most animals possess smooth brains, larger species such as humans, some primates, whales, dolphins, and pigs have developed this distinctive cortical folding. How these intricate folds develop has remained a significant scientific question.

Recent research published in Nature Communications sheds light on this process. The study focuses on the genetic and cellular mechanisms that contribute to cortical folding during brain development. Building on earlier work, scientists examined how variations in gene expression influence neuronal migration and progenitor cell expansion. They found that altering the genes responsible for cellular adhesion molecules affects neuron movement, leading to the formation of grooves similar to those in human brains. Additionally, increasing the number of progenitor cells—the precursors to neurons—exacerbates cortical folding, resulting in complex patterns of gyri and sulci.

This research reveals that a combination of rapid cell growth, neuronal migration, and cellular density jointly shape the cortex. Different types of progenitor cells, such as intermediate progenitors and apical progenitors, influence the formation of specific folds. For example, boosting intermediate progenitors favors sulci formation, while increasing apical progenitors promotes gyrification. These findings were achieved through advanced genetic models, single-cell sequencing, and computer simulations.

According to researcher Seung Hee Chun, the process involves multiple factors working together rather than a single cause. "Our study suggests that cell movement, how tightly neurons migrate, and their density all contribute to forming the brain's characteristic wrinkles," she explains. Understanding these mechanisms not only improves knowledge of brain development but also opens avenues for exploring differences in brain structure among individuals, which may relate to functional and behavioral diversity.

The implications extend to understanding brain evolution and health, as variations in cortical folding are associated with neurological and developmental disorders. Future research may explore how genetic, cellular, and mechanical influences collectively shape the brain's complex architecture, providing insights into both evolution and disease.