The invariance of directional tuning with contrast and coherence.
The responses of motion mechanisms depend not only on the direction of a stimulus, but also on its contrast, coherence and speed. We examined how contrast, coherence and directional selectivity interact by measuring directional tuning psychophysically across a wide range of coherence and contrast levels. We fit data with a simple model that estimated directional tuning bandwidth using contrast and coherence gain parameters that were based on neurophysiological estimates. This model estimated a bandwidth of approximately 90 degrees for directionally selective mechanisms. Bandwidth was invariant across a wide range of contrasts and coherences, as predicted by models of contrast normalization.
Department of Psychology, UC San Diego, La Jolla, CA, USA. ifine@dohenyeyeinstitute.org
I
I
Fine
C M
CM
Anderson
G M
GM
Boynton
K R
KR
Dobkins
D015350:Contrast Sensitivity / Q000502:physiology*; D006801:Humans; D008960:Models, Psychological; D009039:Motion Perception / Q000502:physiology*; D009482:Neurophysiology; D011601:Psychophysics