In this proposal, the candidate plans to expand his theoretical work and to integrate it with experiments of brain activation during waking and sleeping in human subjects. This will be accomplished using state-of- the-art functional magnetic resonance imaging (fMRI). The technique provides a non-invasive measure sensitive to cerebral blood flow. Preliminary studies by the applicant and co-workers include polysomnographic recordings during sleep fMRI. The electrophysiology gives an accurate assessment of state, and visual cortical activation has been observed during sleep. Full brain recordings are planned to map the time course of brain network activation in human wake and sleep with a simultaneous spatial resolution of several cubic millimeters and a temporal resolution of several hundred milliseconds. Differences in activation within and between brain states are anticipated to have relevance to specific cognitive processes. Visual learning tasks will be conducted on normal subjects before sleep and upon spontaneous and induced awakenings. The subjects will undergo sleep fMRI throughout the procedures and several hypotheses of visual processing and plasticity will be tested. The protocol will also be conducted in a group of depressed subjects wherein common neuromodulatory alterations are implicated to underlie sleep and disturbances of mood and cognition. Finally, the results of these studies will be used to develop better integrative models of state-dependent processing and specific experiments will be designed to help these new models.