Chronic insomnia is thought to occur as a result of hyperarousal. While there is a wealth of data to support this position, there is a lack of research to define how hyperarousal interferes with sleep initiation, maintenance, and the perception of sleep quality and quantity. We propose to use Event-related Potential (ERP) techniques to evaluate information processing at sleep onset and during sleep. ERP measures of information processing have been well established in good sleepers; they have not been, however, applied to the problem of insomnia. The goal of the project is to examine the premise that the occurrence and severity of insomnia is fundamentally related to a neurobiologic preparedness to "attend to" and "identify" environmental stimuli. Following an extensive screening, patients with insomnia and good sleepers will participate in two experimental conditions, requiring that they spend four nights in the sleep laboratory over a two week period. ERP data will be gathered prior to, following, and during sleep. The ultimate objectives for this line of research are to determine 1) if insomnia is associated with a failure to inhibit information processing at sleep onset and/or during sleep, 2) if the failure to inhibit information processing at sleep onset and/or during sleep is associated with the occurrence and/or severity of insomnia symptoms, 3) what brain regions are functioning differently so as to give rise to information processing abnormalities, and 4) the extent to which pharmacologic and/or Cognitive Behavioral treatment for insomnia alters information processing abnormalities and/or the associated brain activity. Insomnia is the most prevalent sleep disorder in the general population and may be the most common of all the medical and psychiatric disorders. While considered by some to be merely an annoyance, there is a great deal of evidence that chronic insomnia is a significant risk factor for medical and psychiatric illness. Thus, it is critical to undertake research which may define "what insomnia is" (beyond the subjective experience of the disorder). This may allow for not only the development of better treatments but also for a better understanding of and "how and why" insomnia confers risk for other illnesses. [unreadable] [unreadable] [unreadable]