DISCRIMINATION OF GLOBAL-MOTION SIGNAL STRENGTH

The ability of observers to discriminate differences in global-motion- signal strength(that is the proportion of coherently moving dots in a field of randomly moving dots) was determined for both first and secon d-order stimuli. Observers could accurately discriminate differences i n signal intensity for all reference signal levels tested; 20-100%. A similar pattern of performance was obtained for both types of stimuli. The observed first-order signal-discrimination performance is compati ble with the results of electrophysiological studies that have investi gated the dependence of the firing rate of V5 cells (also called the m iddle temporal area) upon global-motion signal intensity. (C) 1998 Els evier Science Ltd. All rights reserved.