FIGURE-GROUND ACTIVITY IN PRIMARY VISUAL-CORTEX IS SUPPRESSED BY ANESTHESIA

By means of their small receptive fields (RFs), neurons in primary vis ual cortex perform highly localized analyses of the visual scene, far removed from our normal unified experience of vision, Local image elem ents coded by the RF are put into more global context, however, by mea ns of modulation of the responses of the V1 neurons, Contextual modula tion has been shown to follow closely the perceptual interpretation of the scene as a whole, This would suggest that some aspects of context ual modulation can be recorded only in awake and perceiving animals. I n this study, multi-unit activity was recorded with implanted electrod es from primary visual cortex of awake, fixating monkeys viewing textu red displays in which figure and ground regions were segregated by dif ferences in; either orientation or motion, Contextual modulation was i solated from local RF processing, by keeping RP stimulation identical across trials while sampling responses for various positions of the RF relative to figure and ground, Contextual modulation was observed to unfold spatially and temporally in a way that closely resembles the fi gure-ground percept, When recording was repeated, but with the animals anesthetized, the figure-ground related modulatory activity was selec tively suppressed, RF tuning properties, however, remained unaffected, The results show that the modulatory activity is functionally distinc t from the RF properties, V1 thus hosts distinct regimes of activity t hat are mediated by separate mechanisms and that depend differentially on the animal being awake or anesthetized.