Different mechanisms underlie three inhibitory phenomena in cat area 17

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review

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Author(s)

  • Frank Sengpiel
  • Roland J. Baddeley
  • Tobe C.B. Freeman
  • Richard Harrad
  • Colin Blakemore

Detail(s)

Original languageEnglish
Pages (from-to)2067-2080
Journal / PublicationVision Research
Volume38
Issue number14
Online published6 Jul 1998
Publication statusPublished - Jul 1998
Externally publishedYes

Abstract

Recently, it has been proposed that all suppressive phenomena observed in the primary visual cortex (V1) are mediated by a single mechanism, involving inhibition by pools of neurons, which, between them, represent a wide range of stimulus specificities. The strength of such inhibition would depend on the stimulus that produces it (particularly its contrast) rather than on the firing rate of the inhibited cell. We tested this hypothesis by measuring contrast-response functions (CRFs) of neurons in cat V1 for stimulation of the classical receptive field of the dominant eye with an optimal grating alone, and in the presence of inhibition caused by (1) a superimposed orthogonal grating (cross-orientation inhibition); (2) a surrounding iso-oriented grating (surround inhibition); and (3) an orthogonal grating in the other eye (interocular suppression). We fitted hyperbolic ratio functions and found that the effect of cross-orientation inhibition was best described as a rightward shift of the CRF ('contrast-gain control'), while surround inhibition and interocular suppression were primarily characterised as downward shifts of the CRF ('response-gain control'). However, the latter also showed a component of contrast-gain control. The two modes of suppression were differently distributed between the layers of cortex. Response-gain control prevailed in layer 4, whereas cells in layers 2/3, 5 and 6 mainly showed contrast-gain control. As in human observers, surround gratings caused suppression when the central grating was of high contrast, but in over a third of the cells tested, enhanced responses for low-contrast central stimuli, hence actually decreasing threshold contrast.

Research Area(s)

  • Contrast, Gain control, Inhibition, Primary visual cortex, Suppression

Citation Format(s)

Different mechanisms underlie three inhibitory phenomena in cat area 17. / Sengpiel, Frank; Baddeley, Roland J.; Freeman, Tobe C.B. et al.
In: Vision Research, Vol. 38, No. 14, 07.1998, p. 2067-2080.

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review