Durant S, Wall M, Zanker J, 2011, "The effect of motion density in natural scenes on MT/MST brain activity at different contrast levels" Perception 40 ECVP Abstract Supplement, page 96
The effect of motion density in natural scenes on MT/MST brain activity at different contrast levels
S Durant, M Wall, J Zanker
A striking finding from single cell studies is the rapid saturation of response of motion-sensitive area MST with the density of optic flow information (Duffy and Wurtz, 1991). Similar results are found in MT and are reflected psychophysically in human perception in the saturation of motion aftereffects. We measured the effect of motion density on human neural response at different contrast levels, using stimuli formed from natural dynamic scenes. We manipulated the visible proportion of greyscale natural dynamic scenes (25 by 34 deg) by displaying the scenes behind a grey mask punctured by randomly placed 1 deg diameter transparent static hard-edged apertures. We found that areas V1, V2, V3 and V4 showed a large increase in response with the number of apertures, whereas in areas MT and MST the amount of apertures had a much smaller effect. We found the same pattern of results at 10% contrast as at 100%, despite a reduced response overall at low contrast. We found no difference between moving and counterphase-flickering stimuli, suggesting that MT/MST saturates rapidly for dynamic stimuli in general. This suggests that the human brain is well adapted to exploit the dynamic signals from the sparse motion distributions in natural scenes.
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