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Abstract:
Abstract: One of the areas in monkey cortex involved in
calculating egomotion through a dynamic environment is the parietal
area VIP (Schaafsma and Duysens, J. Neurophys 1996). The purpose of
the present study is to see whether VIP is able to account for flow
components due to eye movements in the flow pattern, as has
recently been shown (by Bradley et al, Science, 1996) for MST,
which provides input to VIP. An awake rhesus monkey was required to
either fixate a stationary target projected on a translating dot
pattern, or track the target across a stationary dot pattern. Both
the translation of the pattern and the movement of the target could
occur in one of eight directions, at a constant speed of 16
deg/sec. The resulting flow fields on the monkey's retina were
highly similar in the two conditions, but the physical origin of
the flow differed. Preliminary results show that some neurones
(30%) respond to the retinal flow field, regardless of the physical
causes of this flow (active or passive), whereas, a smaller
proportion of neurones (20%) respond significantly differently
during fixation than when the monkey is tracking a target. The
remaining cells were in between. These findings indicate that VIP
can indeed distinguish between actively induced and passively
viewed optic flow.
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