Spatial frequency properties in area 18 during inactivation of area 17 in cats |
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Authors: | D-Y Ruan A Chabli S Molotchnikoff |
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Institution: | (1) Département de Sciences Biologiques, Université de Montréal, C.P. 6128, succ. Centre-ville, Montréal, Québec, Canada H3C 3J7, CA;(2) Department of Biology, University of Sciences and Technology of China, Hefei, Anhui, 230026 PR China, CN |
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Abstract: | The aim of this investigation was to understand the functions of long horizontal connections projecting from area 17 to area
18 in cats. The animals were anesthetized and prepared for recording single-cell responses to sine-wave gratings in area 18.
Neuronal activity was analyzed under three conditions: prior to, during, and after inactivation of a circumscribed region
of area 17. The latter was depressed with micro-injections of GABA. Cells in both areas were in close retinotopic correspondence.
Cells were classified as simple and complex types. Globally, simple cells were less affected than complex units, and those
which were affected shifted their optimal spatial frequency to higher values. Complex neurons were more often influenced by
the interruption of area 17 input. Namely, the peaks of the tuning curves were displaced on the x-axis to a new optimal spatial frequency. This effect was obtained by a dual change: a decline in the discharge strength to
the optimal spatial frequency and an enhancement to nonoptimal spatial frequency. Contrast sensitivity function disclosed
similar shifts of optimal spatial frequencies. Likewise bandwith, spatial resolution, high cutoff, and low cutoff were modified
to a greater extent in complex cells. It appears that there is no relationship between areas 17/18 orientation difference
and the modifications observed in tuning curves to spatial frequencies. The results suggest that neurons of area 18 may carry
multiple-frequency channels and that area 17 facilitates the emergence of one particular spatial frequency.
Received: 26 February 1996 / Accepted: 27 August 1996 |
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Keywords: | Corticocortical relationships Area 17 Area 18 Spatial frequency Cat |
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