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Published November 1, 1980 | public
Journal Article

Interhemispheric connections of visual cortex in the owl monkey, Aotus trivirgatus, and the bushbaby, Galago senegalensis

Abstract

Anatomical techniques have been used to map within visual cortex the pattern of degenerating axonal terminals produced by surgical section of the splenium of the corpus callosum in the owl monkey, Aotus trivirgatus , and the bushbaby, Galago senegalensis . Previous studies in other species have shown that callosal inputs terminate preferentially in regions where the vertical meridian of the visual field is represented. Such a correspondence can serve as a useful aid for locating the boundaries of visual areas. The goals of this study have been (1) to assess the degree of correspondence between callosal inputs and previously identified vertical meridian representations in the owl monkey and bushbaby, and (2) to gain information from the pattern of callosal inputs concerning the existence and organization of as yet unidentified extrastriate visual areas. In both the owl monkey and the bushbaby, a discrete band of degenerating axonal terminals corresponds precisely to the vertical meridian representation at the V1‐V2 border, and a less precise increase in the density of degenerating axonal terminals corresponds to the vertical meridian representation of extrastriate area MT. A well‐defined band of degeneration on the ventral surface of the owl monkey's cerebral hemisphere corresponds to a previously unknown vertical meridian representation which is shared by two newly identified extrastriate visual areas. Elsewhere in visual cortex the pattern of callosal connections is more complex. Although this pattern may still reflect visual topography, it is not immediately useful for distinguishing areal boundaries.

Additional Information

© 1980 Alan R. Liss, Inc. We thank Jon Kaas for his permission to use unpublished data that he participated in collecting. We are grateful to D.C. Van Essen for use of his histology facilities and A. J. Hudspeth for the use of his microscope. J.F. Baker, A. J. Hudspeth, J. H. R. Maunsell, S. E. Petersen, and D. C. Van Essen made helpful suggestions at various stages in the development of this manuscript. This work was supported by NIH grants NS-12121, NS-00178, and NSF grant BNS-77-15605 to J. M. Allman, a Pew Charitable Trust grant to the Division of Biology, and a Danforth Graduate Fellowship to W. T. Newsome.

Additional details

Created:
August 19, 2023
Modified:
October 20, 2023