Antonino Casile, Michele Rucci
Neural activity appears to be a crucial component for shaping the recep- tive ﬁelds of cortical simple cells into adjacent, oriented subregions alter- nately 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 pres- ence of a Hebbian scheme of synaptic plasticity. Levels of correlation be- tween 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 re- sults suggest an important role for the eye movements occurring during visual ﬁxation in the reﬁnement of orientation selectivity.