Meeting Abstract

P2.64  Friday, Jan. 4  Comparative volumetric analyses of the retinogeniculostriate pathway in mammals HEESY, CP*; WILLMS, J; Midwestern University; Midwestern University cheesy@midwestern.edu

Studies of the relative sizes of brain components in mammals suggest that areas responsible for sensory processing, including visual processing, are correlated with aspects of ecology, especially foraging habits and diet. Some studies suggest that primate orbit convergence and binocular vision are correlated with overall size of the brain as well as components of the visual pathway, such as the lateral geniculate nucleus. However, the question remains whether components of the visual pathway (optic tract, lateral geniculate nucleus, and primary visual cortex) are correlated with orbit convergence and binocular visual field overlap in non-primate mammals. This study examines the relationship between orbit convergence, binocular field overlap, overall brain size, and the volumes of components of the visual pathway (optic tract, lateral geniculate nucleus, and primary visual cortex). Data on orbit orientation are combined with those on overall brain size in primates, carnivorans, chiropterans, insectivorans, artiodactyls, marsupials, and rodents. In addition, data on brain component volumes were collated for a subset of these taxa. Primates differ from other mammals in that orbit convergence is correlated with brain size in anthropoids, and less strongly in strepsirrhines. However, volumetric data on neural components of the visual pathway are correlated with convergence among the taxa included in this study. Binocular taxa have relatively larger optic tracts, lateral geniculate nuclei and primary visual cortices when brain volume is held constant. Primates are not unique in the relationship between binocularity and brain size; however, since primates are the most binocular of the mammals, they also have the relatively largest components of the visual pathway.