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The Journal of Neuroscience, May 1, 2003, 23(9):3881
Electrophysiological Imaging of Functional Architecture in
the Cortical Middle Temporal Visual Area of Cebus
apella Monkey
Antonia Cinira M.
Diogo1, 3,
Juliana G. M.
Soares1,
Alex
Koulakov2,
Thomas D.
Albright3, and
Ricardo
Gattass1
1 Instituto de Biofísica Carlos Chagas Filho,
Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-900, Brazil, and 2 Sloan-Swartz Center for Theoretical
Neurobiology and 3 Howard 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. Responses recorded at successive locations from the same electrode in the array revealed gradual changes
in preferred direction, along with occasional directional reversals.
Comparisons of responses from adjacent electrodes at successive
locations enabled electrophysiological 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. In addition, our results
provide electrophysiological confirmation of map features that have
been documented in other cortical areas and primate species by optical
imaging. Specifically, the tangential organization of directional
selectivity is characterized by slow continuous changes in directional
preference, as well as lines (fractures) and points (singularities)
that fragment continuous regions into 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
Copyright © 2003 Society for Neuroscience 0270-6474/03/2393881-18$05.00/0
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