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Electrophysiological Imaging of Functional Architecture in the Cortical Middle Temporal Visual Area of
 

Summary: Electrophysiological Imaging of Functional Architecture
in the Cortical Middle Temporal Visual Area of
Cebus apella Monkey
Antonia Cinira M. Diogo,1,3 Juliana G. M. Soares,1 Alex Koulakov,2 Thomas D. Albright,3 and Ricardo Gattass1
1Instituto de Biofi´sica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-900, Brazil, and 2Sloan-Swartz Center for
Theoretical Neurobiology and 3Howard Hughes Medical Institute and Systems Neurobiology Laboratories, The Salk Institute for Biological Studies, La Jolla,
California 92037
We studied the spatial organization of directionally selective neurons in the cortical middle temporal visual area (area MT) of the Cebus
monkey. We recorded neuronal activity from multielectrode arrays as they were stepped through area MT. The set of recording sites in
each array penetration described a plane parallel to the cortical layers. At each recording site, we determined the preferred direction of
motion.Responsesrecordedatsuccessivelocationsfromthesameelectrodeinthearrayrevealedgradualchangesinpreferreddirection,
along with occasional directional reversals. Comparisons of responses from adjacent electrodes at successive locations enabled electro-
physiological imaging of the two-dimensional pattern of preferred directions across the cortex. Our results demonstrate a systematic
organization for directionality in area MT of the New World Cebus monkey, which is similar to that known to exist in the Old World
macaque.Inaddition,ourresultsprovideelectrophysiologicalconfirmationofmapfeaturesthathavebeendocumentedinothercortical
areas and primate species by optical imaging. Specifically, the tangential organization of directional selectivity is characterized by slow
continuouschangesindirectionalpreference,aswellaslines(fractures)andpoints(singularities)thatfragmentcontinuousregionsinto
patches. These electrophysiological methods also allowed a direct investigation of neuronal selectivities that give rise to map features. In
particular, our results suggest that inhibitory mechanisms may be involved in the generation of fractures and singularities.
Key words: extrastriate cortex; directional selectivity; visual system; primates; multielectrode array; functional maps

  

Source: Albright, Tom - Vision Center Laboratory, Salk Institute for Biological Studies

 

Collections: Biology and Medicine