We wish to seek evidence of a neuroanatomical basis for the separation of the sedative/hypnotic and amnesic effects of propofol by imaging electrophysiologic and regional cerebral blood flow (rCBF) changes to identify these. Our main hypothesis is that there are differing neuroanatomical regions mediating drug-induced sedation and amnesia, and that these can be identified by specific changes in electrophysiology and rCBF. Electrophysiologic changes will be mapped using a validated electroencephalographic (EEG) mapping technique, Low Resolution brain Electromagnetic Tomography (LORETA). (1) Changes in brain activity will be identified with high spatial resolution using magnetic resonance imaging (MRI) and statistical parametric mapping (SPM). (2) To identify key regions out of possibly many exhibiting changes in brain activity during propofol administration, we plan to manipulate drug-induced sedation by using thiopental, a sedative drug with few memory effects active at the same receptors as propofol.