Report

The Contribution of Noise to Contrast Invariance of Orientation Tuning in Cat Visual Cortex

+ See all authors and affiliations

Science  08 Dec 2000:
Vol. 290, Issue 5498, pp. 1968-1972
DOI: 10.1126/science.290.5498.1968

You are currently viewing the abstract.

View Full Text

Via your Institution

Log in through your institution

Log in through your institution


Abstract

Feedforward models of visual cortex appear to be inconsistent with a well-known property of cortical cells: contrast invariance of orientation tuning. The models' fixed threshold broadens orientation tuning as contrast increases, whereas in real cells tuning width is invariant with contrast. We have compared the orientation tuning of spike and membrane potential responses in single cells. Both are contrast invariant, yet a threshold-linear relation applied to the membrane potential accurately predicts the orientation tuning of spike responses. The key to this apparent paradox lies in the noisiness of the membrane potential. Responses that are subthreshold on average are still capable of generating spikes on individual trials. Unlike the iceberg effect, contrast invariance remains intact even as threshold narrows orientation selectivity. Noise may, by extension, smooth the average relation between membrane potential and spike rate throughout the brain.

  • * To whom correspondence should be addressed. E-mail: ferster{at}northwestern.edu

View Full Text

Related Content