Each cell in the visual system has a receptive field, a portion of the retina to which it responds. Each cell in the visual system responds to specific features of a stimulus in its receptive field, such as shape, color, or movement. Separate pathways in the visual system attend to different aspects of the visual system. Certain kinds of brain damage can impair specific aspects of visual perception. Visual cortex is that part of the cerebral cortex that receives the most direct input from the visual system.
Binocular rivalry in human vision-- National Eye Institute (2001-2005)
Randolph Blake, Ph.D., Principal Investigator
Visual system organization and development--National Eye Institute (1978-2008)
Vivien Casagrande, Ph.D., Principal Investigator
Mechanisms of retinal synaptic plasticity--National Eye Institute (1991-2003)
Douglas McMahon, Ph.D., Principal Investigator
This project investigates the mechanisms by which glutamatergic and electrical synapses are modulated by light adapting signals in retinal neurons and circuits.
Saccade target selection--frontal cortex--National Eye Institute (1991-2005)
Jeffrey Schall, Ph.D., Principal Investigator
The goal of these experiments is to understand how the brain selects targets for eye movements. A recently published paper in the Journal of Neurophysiology describes Schall's findings on the time course of the visual discrimination process. His research demonstrated a measurement of when the activity of single neurons in the front cortex registers the location of the target within an array of distracting stimuli. This time represents the outcome and conclusion of perceptual processing. He further showed that the reaction time of the monkeys to shift gaze to the target was not accounted for by the duration of the perceptual processing. Much of the delay and most of the variability of reaction time was attributed to a stage of response preparation that followed perceptual processing. This work represents the first direct demonstration based on neuronal activity that reaction time can be partitioned into separate stages. If the time of target discrimination that he has determined is a reliable measure of the conclusion of perceptual processing, then it is possible to address a key theoretical question regarding the precise relation of the stages of processing. Does information flow discretely form one state to the next only when the earlier stage is completed? Or does information flow continuously form one stage to the next as each bit is processed? More particularly, when and how does sensory processing influence response preparation? Recordings from multiple single neurons can provide data that is more definitive than heretofore.
National Eye
Institute
Vision Science:
An Internet Resource for Research in Human and Animal Vision