Understanding the pathophysiology of schizophrenia is one of the most compelling challenges facing current psychiatric research. Several electrophysiological and neuroimaging studies have explored the brain activity of schizophrenics and controls while these subjects performed various cognitive tasks to identify brain abnormalities specific for schizophrenia. In this study, schizophrenics and controls will be investigated while asleep. Sleep EEG recordings minimize possible waking-related confounding factors, including level of attention and presence of psychotic symptoms, and offer the opportunity to study sleep-specific rhythms such as sleep spindles. In a recent study with a 256 channel high density EEG (hd-EEG), Ferrarelli et al. (AJP 2007) revealed that schizophrenics (n=18) had a significant reduction in several spindle parameters in a centroparietal area compared to controls (n=17) during the first sleep episode. Other recent studies by Massimini et al. have demonstrated the feasibility of combining TMS with hd-EEG to investigate changes of effective connectivity in healthy subjects between waking and sleep (Science 2005, PNAS in press). In this study, hd-EEG recordings will be performed in schizophrenics and controls with two aims: 1) studying spontaneous brain activity, particularly spindles, during sleep 2) exploring the dynamics of evoked responses during sleep, especially the modulation of spindle activity following an evoked potential. Hd-EEG will be used to assess the stability of the spindle pattern over time and to investigate larger groups, including patients without schizophrenia taking antipsychotics. Evoked activity during sleep will be explored using both auditory tones and TMS to induce slow oscillations or K-complexes, which are often followed by spindles. It is expected that a comprehensive investigation of spontaneous and evoked spindle activity will provide a parameter which minimizes the overlap between schizophrenics and controls.