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Evolution Amplified Processing with Temporally Dispersed Slow Neuronal Connectivity in Primates
Roberto Caminiti, Hassan Ghaziri, Ralf Galuske, Patrick R. Hof and Giorgio M. Innocenti
Proceedings of the National Academy of Sciences of the United States of America
Vol. 106, No. 46 (Nov. 17, 2009), pp. 19551-19556
Published by: National Academy of Sciences
Stable URL: http://www.jstor.org/stable/25593230
Page Count: 6
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The corpus callosum (CC) provides the main route of communication between the 2 hemispheres of the brain. In monkeys, chimpanzees, and humans, callosal axons of distinct size interconnect functionally different cortical areas. Thinner axons in the genu and in the posterior body of the CC interconnect the prefrontal and parietal areas, respectively, and thicker axons in the midbody and in the splenium interconnect primary motor, somatosensory, and visual areas. At all locations, axon diameter, and hence its conduction velocity, increases slightly in the chimpanzee compared with the macaque because of an increased number of large axons but not between the chimpanzee and man. This, together with the longer connections in larger brains, doubles the expected conduction delays between the hemispheres, from macaque to man, and amplifies their range about 3-fold. These changes can have several consequences for cortical dynamics, particularly on the cycle of interhemispheric oscillators.
Proceedings of the National Academy of Sciences of the United States of America © 2009 National Academy of Sciences