While working on a topic about visual-vestibular interaction, a
question concerning the dissociation of the procession of visual
features popped into my mind. I was hoping anyone in this newsgroup
might be able to help me or suggest any relevant literature.
Movement- and colour detection happens at different and distant parts in
the brain (ventral stream and dorsal stream respectively). We know that
movement detectors in the brain are colourblind to a certain extent but
that the corresponding areas interact with other visual areas (inter
alia colour detectors) via intercortical connections.
A subject that looks at moving black and white stimuli (like moving
black and white vertical bars) perceives these stimuli as moving. I was
wondering what happens if these stimuli consist of isoluminant coloured
bars (like for instance red and green bars) instead of B/W stimuli.
Movement detectors need different luminant stimuli in order to see a
contrast between stimuli and therefore perceive a change in the visual
field. Hence, if the difference in luminance of the stimuli is a
necessary condition to perceive motion, coloured moving stimuli with the
same luminance should be perceived as stationary. My concern is the
interaction between the ventral and dorsal stream. Do movement detectors
receive information about colour despite their colour-blindness? If this
is the case, then movement would be detected although the stimuli are
equiluminant. However, one way to obtain motion-blindness might be to
use a random-dot kinematogram of equiluminant red and green dots. In
this kind of stimulation, the perception of motion and contrast is
induced by correlating the movement of a fixed number of dots of
otherwise uncorrelated moving dots. I haven't found any literature
concerning my questions. Does anyone know about publications concerning
the perception of movement of isoluminant coloured stimuli, maybe
involving random-dot kinematograms?
If anyone knows where to obtain or download software to produce
isoluminant stimuli like gratings or coloured random-dot-kinematograms,
I would appreciate a short message telling me the URL.
Thanks a lot for any help.
Tobi
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Tobias Kalenscher
e-mail: kalensch at uni-duesseldorf.de
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