1Anthropology Department, University of California, San Diego, 2Anthropology Department, University of South Carolina, Columbia, 3Anthropology Department, The George Washington University, Washington DC, 4National Museum of Health and Medicine, Armed Forces Institute of Pathology, Washington, DC
Saturday All day, Plaza Level
We examined the development of the spatial organization of neurons in four regions of cortex (frontal pole [BA10], primary motor [M1], primary somatosensory [S1], and prestriate visual cortex [V2]) in fourteen chimpanzees and sixteen humans of both sexes. Horizontal spacing distance (HSD) and gray level ratio (GLR) of neurons in layer III were measured in Nissl-stained specimens that ranged in age from birth to 11 years of age. In chimpanzees, HSD increases during the first few years of life in BA10, M1, and S1, while spacing distance in V2 does not. In humans, HSD in the frontal pole increases during the protracted development of the human frontal lobe, while there were no age-related changes in the other three regions. The HSD of neurons has been linked to modular and vertical characteristics of the cortex. Differences in the width of spacing between cortical areas reflect differences in anatomical organization. Our previous study of adults suggested that the human brain is characterized by an increase in the space available for interconnectivity with neurons in the prefrontal cortex compared to apes. This may be a consequence of the prolonged developmental trajectory of the human frontal lobe.
Work funded by the Chancellor’s Interdisciplinary Collaboratory Scholarship at UCSD and by the Kavli Institute for Brain and Mind at UCSD.