A new study conducted by researchers at the University of Bath has found that enlargement of the visual cortex of the brain in primates is associated with increased visual acuity, suggesting that increases in the size of brain regions are associated with enhanced function. The study has been published in Frontiers in Neuroanatomy.
While an overall relationship between brain size and cognitive ability is apparent in primates, little is known about the relevance of the size of specific cortical regions in regard to function. In order to shed some light on this poorly understood area, researchers compared the visual cortex of numerous primate species, including humans, and used assessments of visual acuity and the perception of visual illusions provided by other studies as measures of cortical function.
The researchers found that as the size of the visual cortex increased, the number of neurons in this region also increased. However, with this increase in size actually came a decrease in overall neuron density. This is likely because the cell bodies (neuronal soma) are more sparsely distributed, resulting in more space being occupied by interneuronal connections. They suggest that this increase in cell number and neuronal connections may allow greater brain plasticity.
“Primates with a bigger visual cortex have better visual resolution, the precision of vision, and reduced visual illusion strength,” said lead author Alexandra de Sousa in a news-release. “In essence, the bigger the brain area, the better the visual processing ability.” She explains that the increase in neuronal connections that likely occur in larger brains allow for increasingly complex interneuronal communications to be made that allow for more accurate visual perception.
According to co-author Michael Proulx, this study provides a framework that ties brain structure and function together. “The theory of brain size that we discuss can be tested in the future with more behavioral tests of other species, gathering more comparative neuroanatomical data, and by testing other senses and multi-sensory perception, too,” he added.