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Abstract:
Neural activity appears to be a crucial component for shaping
the receptive fields of cortical simple cells into adjacent,
oriented subregions alternatively receiving ON- and OFF-center
excitatory geniculate inputs. It is known that the orientation
selective responses of V1 neurons are refined by visual
experience. After eye opening, the spatiotemporal structure of
neural activity in the early stages of the visual pathway depends
both on the visual environment and on how the environment is
scanned. We have used computational modeling to investigate how
eye movements might affect the refinement of the orientation
tuning of simple cells in the presence of a Hebbian scheme of
synaptic plasticity. Levels of correlation between the activity
of simulated cells were examined while natural scenes were
scanned so as to model sequences of saccades and fixational eye
movements, such as microsaccades, tremor and ocular drift. The
specific patterns of activity required for a quantitatively
accurate development of simple cell receptive fields with
segregated ON and OFF subregions were observed during fixational
eye movements, but not in the presence of saccades or with static
presentation of natural visual input. These results suggest an
important role for the eye movements occurring during visual
fixation in the refinement of orientation selectivity.
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