The Journal of Neuroscience, June 15, 2000, 20(12):4708-4720
Modeling LGN Responses during Free-Viewing: A Possible Role of
Microscopic Eye Movements in the Refinement of Cortical Orientation
Selectivity
Michele
Rucci1,
Gerald
M.
Edelman2, and
Jonathan
Wray2
1 Department of Cognitive and Neural Systems, Boston
University, Boston, Massachusetts 02215, and 2 The
Neurosciences Institute, San Diego, California 92121
Neural activity appears to be essential for the normal development
of the orientation-selective responses of cortical cells. It has been
proposed that the correlated activity of LGN cells is a crucial
component for shaping the receptive fields of cortical simple cells
into adjacent, oriented subregions alternately receiving ON- and
OFF-center excitatory geniculate inputs. After eye opening, the
spatiotemporal structure of neural activity in the early stages of the
visual pathway depends not only on the characteristics of the
environment, but also on the way the environment is scanned. In this
study, we use computational modeling to investigate how eye movements
might affect the refinement of orientation tuning in the presence of a
Hebbian scheme of synaptic plasticity. Visual input consisting of
natural scenes scanned by varying types of eye movements was used to
activate a spatiotemporal model of LGN cells. In the presence of
different types of movement, significantly different patterns of
activity were found in the LGN. Specific patterns of correlation
required for the development of segregated cortical receptive field
subregions were observed in the case of micromovements, but were not
seen in the case of saccades or static presentation of natural visual
input. These results suggest an important role for the eye movements
occurring during fixation in the refinement of orientation selectivity.
Key words:
visual development; microsaccade; natural visual
experience; computer model; cat; visual fixation; Hebbian
plasticity
Copyright © 2000 Society for Neuroscience 0270-6474/00/20124708-13$05.00/0