Modulation of responses to optic flow in area 7a by retinotopic and oculomotor cues in monkey |
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Authors: | Read HL; Siegel RM |
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Institution: | Center for Molecular and Behavioral Neuroscience, Rutgers University, Newark, NJ 07102, USA. |
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Abstract: | Perception of two- and three-dimensional optic flow critically depends upon
extrastriate cortices that are part of the 'dorsal stream' for visual
processing. Neurons in area 7a, a sub-region of the posterior parietal
cortex, have a dual sensitivity to visual input and to eye position. The
sensitivity and selectivity of area 7a neurons to three sensory cues -
optic flow, retinotopic stimulus position and eye position - were studied.
The visual response to optic flow was modulated by the retinotopic stimulus
position and by the eye position in the orbit. The position dependence of
the retinal and eye position modulation (i.e. gain field) were quantified
by a quadratic regression model that allowed for linear or peaked receptive
fields. A local maximum (or minimum) in both the retinotopic fields and the
gain fields was observed, suggesting that these sensory qualities are not
necessarily linearly represented in area 7a. Neurons were also found that
simply encoded the eye position in the absence of optic flow. The spatial
tuning for the eye position signals upon stationary stimuli and optic flow
was not the same, suggesting multiple anatomical sources of the signals.
These neurons can provide a substrate for spatial representation while
primates move in the environment.
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