Contrast Dependence of Suppressive Influences in Cortical Area MT of Alert Macaque
- 1 March 2005
- journal article
- Published by American Physiological Society in Journal of Neurophysiology
- Vol. 93 (3), 1809-1815
- https://doi.org/10.1152/jn.00629.2004
Abstract
Visual neurons are often characterized in terms of their tuning for various stimulus properties, such as shape, color, and velocity. Generally, these tuning curves are further modulated by the overall intensity of the stimulus, such that increasing the contrast increases the firing rate, up to some maximum. In this paper, we describe the tuning of neurons in the middle temporal area (MT or V5) of macaque visual cortex for moving stimuli of varying contrast. We find that, for some MT neurons, tuning curves for stimulus direction, speed, and size are shaped in part by suppressive influences that are present at high stimulus contrast but weak or nonexistent at low contrast. For most neurons, the suppression is direction-specific and strongest for large, slow-moving stimuli. The surprising consequence of this phenomenon is that some MT neurons actually fire more vigorously to a large low-contrast stimulus than to one of high contrast. These results are consistent with recent perceptual observations, as well as with information-theoretic models, which hypothesize that the visual system seeks to reduce redundancy at high contrast while maintaining sensitivity at low contrast.Keywords
This publication has 41 references indexed in Scilit:
- Visual Cortex Neurons of Monkeys and Cats: Temporal Dynamics of the Spatial Frequency Response FunctionJournal of Neurophysiology, 2004
- Estimating Target Speed from the Population Response in Visual Area MTJournal of Neuroscience, 2004
- Coding of Horizontal Disparity and Velocity by MT Neurons in the Alert MacaqueJournal of Neurophysiology, 2003
- Nature and Interaction of Signals From the Receptive Field Center and Surround in Macaque V1 NeuronsJournal of Neurophysiology, 2002
- Motion illusions as optimal perceptsNature Neuroscience, 2002
- Segregation of Object and Background Motion in Visual Area MT: Effects of Microstimulation on Eye MovementsNeuron, 2000
- Contrast dependence of contextual effects in primate visual cortexNature, 1997
- Visual cortex neurons in monkey and cat: Effect of contrast on the spatial and temporal phase transfer functionsVisual Neuroscience, 1995
- Human speed perception is contrast dependentVision Research, 1992
- The Standard Deviation of Luminance as a Metric for Contrast in Random-Dot ImagesPerception, 1990