Computer analysis of human depth EEG in different sleep stages

This study compares delta (< 4 Hz), theta (4-8 Hz), alpha (8-12 Hz) and beta (12-20 Hz) band EEG signals during wakefulness, rapid-eye-movement (REM) sleep, and stage 1 and stage 2 non-REM sleep recorded from both surface and depth electrodes in patients with drug-resistant partial seizures. Computer analysis utilizing Fast Fourier Transforms (FFT) was performed with the Neurovision software developed for this purpose. Mean amplitudes were calculated for each of the frequency bands. Preliminary analysis was performed with emphasis on the presence and characteristics of theta activity in the hippocampus of the brain. Results demonstrate theta wave activity in the hippocampus with an increase of theta activity in REM sleep as compared to non-REM sleep (stages 1 and 2).