Vision

Action potentials generated by neurons in the cerebral cortex eventually give rise to conscious sensations. Understanding this process requires both a description of what information is represented in the activity of single neurons, and a description of the mechanism by which that representation is generated. Binocular stereopsis (the ability to perceive depth by combining images from the two eyes) is an attractive model system to study both the nature and mechanism of the cortical representation for several reasons:

• It seems likely that we can explain the mechanisms that underlie disparity selectivity in single neurons of the primary visual cortex.


• The psychophysical properties have been extensively studied in humans and monkeys. Many of these properties are not straightforwardly reflected in the activity of single neurons, at least in V1.


• Extensive computational work offers mechanisms that can bridge the gap between 1) and 2).


• Several lines of evidence indicate that neurons in extrastriate cortex are more closely linked to the perception of stereoscopic depth than V1 neurons. Understanding how these responses are derived from neurons in V1 may then lead to a mechanistic description of how the brain generated the signals that give rise to the perception of depth.

With a view to generating this description, we record action potentials from single cortical neurons in awake animals trained to perform stereoscopic discrimination tasks. Quantitative modelling is then used to describe both the response properties of individual neurons, and their relationship to psychophysical judgments.

Staff	Title	E-mail
Bruce G. Cumming	Vision Section Chief	bgc@lsr.nei.nih.gov
Ali Moeeny	Post Doctoral Fellow	moeenya@nei.nih.gov
Boris M. Sheliga	Staff Scientist	bms@nei.nih.gov