How does the brain sustain a visual percept?

Perception involves the processing of sensory stimuli and their translation into conscious experience. A novel percept can, once synthesized, be maint ained or discarded from awareness. We used event-related funtional magnetic resonance imaging to separate the neural responses associated with the mai ntenance of a percept, produced by single-image, random-dot stereograms, fr om the response evoked at the onset of the percept. The latter was associat ed with distributed bilateral activation in the posterior thalamus and regi ons in the occipito-temporal, parietal and frontal cortices. In contrast, s ustained perception was associated with activation of the pre-frontal corte x and hippocampus. This observation suggests that sustaining a visual perce pt involves neuroanatomical systems which are implicated in memory function and which are distinct from those engaged during perceptual synthesis.