Evolution of the cerebellar cortex: The selective expansion of prefrontal-projecting cerebellar lobules

It has been suggested that interconnected brain areas evolve in tandem because evolutionary pressures act oil complete functional systems rather than oil individual brain areas. The cerebellar cortex has reciprocal connections with both the prefrontal cortex and motor cortex. forming independent loops with each. Specifically, III Capuchin monkeys cerebellar cortical lobules Crus I and Crus 11 connect with prefrontal cortex. whereas the primary motor cortex connects with cerebellar lobules V, VI. VIIb). and VIIIa Comparisons of extant primate species suggest that the prefrontal cortex has expanded more than cortical motor areas in human evolution Given the enlargement of the prefrontal cortex relative to motor Cortex in humans, our hypothesis Would predict corresponding volumetric increases in the parts of the cerebellum Connected to the prefrontal cortex, relative to cerebellar lobules connected to the motor cortex We tested the hypothesis by comparing the volumes of cerebellar lobules in Structural MRI scans in capuchins chimpanzees and humans The fractions of cerebellar volume occupied by Crus I and Crus 11 were significantly larger in humans compared to chimpanzees and capuchins Our results therefore support the hypothesis that in the corticocerebellar system, functionally related structures evolve in concert with each other The evolutionary expansion of these prefrontal-projecting cerebellar territories might contribute to the evolution Of the higher cognitive functions of humans (C) 2009 Elsevier Inc All rights reserved