We recorded single-neuron and multi-unit activity in cortical motion-processing area MT (V5) of anaesthetized paralyzed macaque monkeys in response to moving sinewave gratings modulated in both luminance and chromatic domain. The activity of MT neurons
was highly dependent on luminance contrast. In 3 of 4 animals we found (isoluminant) modulations that did not activate any neuron. With the equivalent visual stimuli, in contrast, speed judgments and onset parameters of evoked optokinetic eye movements in
human subjects were largely independent of luminance modulation. Motion of every grating (including isoluminant) was readily visible for all but one observer. Our results do not suggest a critical role of area MT in the processing of chromatic motion and
do not support the idea of MT as a universal substrate for visual motion representation in the primate cerebral cortex.