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Effects of selective pressure block of Y-type optic nerve fibers on the receptive-field properties of neurons in area 18 of the visual cortex of the cat

Published online by Cambridge University Press:  02 June 2009

B. Dreher ,
A. Michalski ,
B. G. Cleland  and
W. Burke
B. Dreher
Affiliation:
Department of Anatomy, The University of Sydney, N.S.W. 2006, Australia
A. Michalski
Affiliation:
Department of Anatomy, The University of Sydney, N.S.W. 2006, Australia
B. G. Cleland
Affiliation:
Department of Physiology, The University of Sydney, N.S.W. 2006, Australia
W. Burke
Affiliation:
Department of Anatomy, The University of Sydney, N.S.W. 2006, Australia Department of Physiology, The University of Sydney, N.S.W. 2006, Australia
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Abstract

Recordings were made from single neurons in area 18 of anesthetized cats (N2O/O2 mixture supplemented by continuous intravenous infusion of barbiturate) in which one optic nerve had been pressure blocked to selectively block conduction in the largest (Y-type) fibers. Cortical neurons were stimulated visually via the normal eye or via the eye with the pressure-blocked optic nerve (“Y-blocked eye”). Several properties of the receptive fields such as their spatial organization (S or C cells), orientation tuning, and the presence and strength of end-zone inhibition appear to be unaffected by removal of the Y input. By contrast, the removal of the Y input resulted in a small but significant reduction in the size of the discharge field and in the direction-selectivity index. In three respects, peak response discharge rate, eye dominance, and velocity sensitivity, removal of the Y input had strong and highly significant effects. Thus, the mean peak discharge frequency of responses evoked by the stimulation of binocular neurons via the Y-blocked eye was significantly lower than that of responses evoked by the stimulation via the normal eye. Accordingly, the eye-dominance histogram was shifted markedly towards the normal eye (more so than in the homologous experiment conducted on area 17 — Burke et al., 1992). Finally, the mean preferred velocity of responses of cells activated via the normal eye was in the vicinity of 145 deg/s, whereas for cells activated via the Y-blocked eye the value was about 35 deg/s. Overall, the results of the present study imply that (1) apart from Y-type excitatory input there are significant excitatory non-Y-inputs to area 18; these inputs at least partially consist of indirect X-type input relayed via area 17; (2) in neurons of area 18 that receive both Y-type and non-Y-type excitatory inputs, the Y-type input has a major influence on strength of the response and velocity sensitivity and a lesser influence on the direction selectivity and size of the discharge fields; and (3) area 18 contains mechanisms determining such receptive-field properties as S- or C-type organization, orientation tuning, and direction selectivity which can be accessed either by the Y input or by non-Y input.

Keywords

Cortical area V2BinocularityOrientation selectivityDirection selectivityVelocity sensitivityConvergence of X and Y inputsAssociational connections
Type
Research Articles
Information
Visual Neuroscience , Volume 9 , Issue 1 , July 1992 , pp. 65 - 78
Copyright
Copyright © Cambridge University Press 1992

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