 |
|
|
|
||||||||||||
 |
|||||||||||||||
|
 
University of Pennsylvania
We have found that the responses of about half of the direction selective cells in primary visual cortex can be strongly influenced, sometimes even overwhelmed, by moving stimuli situated entirely outside the CRF. The centers and surrounds have an opponent organization--surround motion in the null direction facilitates the center response and surround motion in the preferred direction inhibits the center response. By estimating spatiotemporal receptive field structure both with and without effective surround stimuli, we have determined that the surround effects are effected by changes in gain of the CRF mechanism rather than changes in RF structure. Thus the filters are scalable but not tunable. In the intracellular studies, we are using spike-triggered averaging of membrane potential locked to extracellular activity of groups of neurons recorded extracellularly at various distances in visual space and as a function of orientation difference. With this approach, we hope to establish patterns of connectivity and to explore the synaptic mechanisms underlying context dependency in visual cortex.
Graduate Groups |
 |
|||||||||||||
 |
|||||||||||||||
|
home | faculty | grads | undergrads | departments | institutes | courses | talks Contact: perception@psych.upenn.edu |
|||||||||||||||
