STATE-DEPENDENT RECEPTIVE-FIELD RESTRUCTURING IN THE VISUAL-CORTEX

To extract important information from the environment on a useful time scale, the visual system must be able to adapt rapidly to constantly c hanging scenes. This requires dynamic control of visual resolution pos sibly at the level of the responses of single neurons. Individual cell s in the visual cortex respond to Light stimuli on particular location s (receptive fields) on the retina, and the structure of these recepti ve fields can change in different contexts(1-4). Here we show experime ntally that the shape of receptive fields in the primary visual cortex of anaesthetized cats undergoes significant modifications, which are correlated with the general state of the brain as assessed by electroe ncephalography: receptive fields are wider during synchronized states and smaller during non-synchronized states. We also show that cortical receptive fields shrink over time when stimulated with hashing light spots. Finally, by using a network model we account for the changing s ize of the cortical receptive fields by dynamically rescaling the leve ls of excitation and inhibition in the visual thalamus and cortex. The observed dynamic changes in the sizes of the cortical receptive field could be a reflection of a process that adapts the spatial resolution within the primary visual pathway to different states of excitability .