Influence of stimulus speed upon the antagonistic surrounds of area MT/V5 neurons.
We investigated the effect of stimulus speed upon surround antagonism in macaque MT/V5 neurons, using probe stimuli placed at different positions in the surround. Their speed was varied, while the stimulation of the excitatory receptive field (RF) was held at optimal speed. Most Surrounds proved asymmetric, arising from a single region on one side of RF, although bilaterally and circularly symmetric surrounds were occasionally observed. Surround organization was generally retained at faster or slower surround speeds. Speed-dependent changes usually entailed diminished position dependence of surround influence, consequent to reduced surround effect at the position producing maximum inhibition. The effect of a stimulus covering the entire surround was much less dependent upon motion speed. Results show that surround non-uniformity is a robust finding in MT/V5 and endows neurons with multiple mechanisms for extracting surface orientation in depth.
Xiao
D K
DK
Katholieke Universiteit Leuven, School of Medicine, Laboratorium voor Neuro- en Psychofysiologie, Belgium.
Raiguel
S
S
Marcar
V
V
Orban
G A
GA
D000818:Animals; D004594:Electrophysiology / Q000379:methods; D008252:Macaca fascicularis; D008297:Male; D009039:Motion Perception; D009474:Neurons / Q000502:physiology*; D009949:Orientation; D010775:Photic Stimulation; D013997:Time Factors; D014793:Visual Cortex / Q000502:physiology*