Chromatic sensitivity of neurones in area MT of the anaesthetised macaque monkey compared to human motion
perception
I. Riecansky, A. Thiele, C. Distler & K.-P. Hoffmann
Exp.Brain Res.167:504-525, 2005
- We recorded activity from neurones in cortical motion-processing areas, middle temporal area (MT) and middle
posterior superior temporal sulcus (MST), of anaesthetised and paralysed macaque monkeys in response to moving
sinewave gratings modulated in luminance and chrominance. The activity of MT and MST neurones was highly dependent
on luminance contrast. In three of four animals isoluminant chromatic modulations failed to activate MT/MST neurones
significantly. At low luminance contrast a systematic dependence on chromaticity was revealed, attributable mostly
to residual activity of the magnocellular pathway. Additionally, we found indications for a weak S-cone input,
but rod intrusion could also have made a contribution. In contrast to the activity of MT and MST neurones, speed
judgments and onset amplitude of evoked optokinetic eye movements in human subjects confronted with equivalent
visual stimuli were largely independent of luminance modulation. Motion of every grating (including isoluminant)
was readily visible for all but one observer. Similarity with the activity of MT/MST cells was found only for motion-nulling
equivalent luminance contrast judgments at isoluminance. Our results suggest that areas MT and MST may not be involved
in the processing of chromatic motion, but effects of central anaesthesia and/or the existence of intra- and inter-species
differences must also be considered.
|
