This study will evaluate how the state of being completely deprived of sleep has an effect on recordings of magnetoencephalography (MEG) and electroencephalography (EEG), in relation to how alert someone is and how sleepy someone perceives himself or herself to be. EEG measures electronic potential differences on the scalp. On the other hand, MEG is a non-invasive technique for recording the activity of neurons in the brain, through recording of magnetic fields caused by synchronized neural currents. It has the ability to detect seizures. Because magnetic signals of the brain vary, this technique must balance two key problems: weakness of the signal and strength of the noise. The EEG is sensitive to extra-cellular volume currents, whereas the MEG primarily registers intra-cellular currents. Because electrical fields are quite dependent on the conductive properties of the tissues, and magnetic fields are significantly less distorted by tissue, the MEG has better spatial resolution. There is a great deal of evidence that EEG and MEG provide complementary data about underlying currents of ions.

The complex relationship of sleep and epilepsy is well known. Sleep has been used for many years as a powerful EEG activator. Many researchers have supported the hypothesis that there is a specific activating effect of sleep deprivation on epileptic discharges. Sleep deprivation is defined as a sleepless state of longer than 24 hours. The increased use of MEG in diagnosis could improve the procedure for evaluating patients before surgery for epilepsy, by making invasive studies less necessary.

Patients 18 years of age or older, with a diagnosis of epilepsy and with a documented last routine EEG (at least 2 weeks earlier) and routine EEG on the day of a baseline MEG-EEG without interictal epileptiform discharges (IEDs) may be eligible for this study.

Participants will be rated according to the Epworth, Stanford, and Karolinska Sleepiness Scales, to determine their subjective sleepiness. They will be randomly assigned to stay awake all night or sleep in the hospital overnight. That is, a sleep deprivation and non-sleep deprivation synchronized MEG-EEG recording will be performed in random order. Then the sequence of sleep deprivation and non-sleep deprivation will be reversed within 14 to 21 days. During the recordings, the patient will either sit or lie with his or her head in a helmet covering the entire head, with openings for the eyes and ears. Brain magnetic fields will be recorded with a 275-channel OMEGA system. Throughout the session, visual and two-way audio communication will be maintained with the patient. Recording sessions will last 90 to 180 minutes, with the patient allowed to take breaks after at least 10 minutes in a scanner. Attempts will be made to encourage patients to stay awake and sleep for about the same amount of time during each recording, to acquire comparable amounts of sleep and awake recordings.