Spontaneously emerging cortical representations of visual attributes

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Abstract
Spontaneous cortical activity—ongoing activity in the absence of intentional sensory input—has been studied extensively1, using methods ranging from EEG (electroencephalography)2,3,4, through voltage sensitive dye imaging5,6,7, down to recordings from single neurons8,9. Ongoing cortical activity has been shown to play a critical role in development10,11,12,13,14, and must also be essential for processing sensory perception, because it modulates stimulus-evoked activity5,15,16, and is correlated with behaviour17. Yet its role in the processing of external information and its relationship to internal representations of sensory attributes remains unknown. Using voltage sensitive dye imaging, we previously established a close link between ongoing activity in the visual cortex of anaesthetized cats and the spontaneous firing of a single neuron6. Here we report that such activity encompasses a set of dynamically switching cortical states, many of which correspond closely to orientation maps. When such an orientation state emerged spontaneously, it spanned several hypercolumns and was often followed by a state corresponding to a proximal orientation. We suggest that dynamically switching cortical states could represent the brain's internal context, and therefore reflect or influence memory, perception and behaviour.