High Frequency EEG Activity during Sleep: Characteristics in Schizophrenia and Depression

Abstract

Previous studies indicate that high frequency power (>20Hz) in the electroencephalogram (EEG) are associated with feature binding and attention. It has been hypothesized that hallucinations and perceptual abnormalities might be linked to irregularities in fast frequency activity. This study examines the power and distribution of high frequency activity (HFA) during sleep in healthy control subjects and unmedicated patients with schizophrenia and depression. This is a post-hoc analysis of an archival database collected under identical conditions. Groups were compared using multivariate analyses of covariance (MANCOVA) using group frequency by stage analysis. A multiple regression analyzed the association between HFA power and clinical symptoms. Schizophrenic (SZ) and major depressive disorder (MDD) patients showed significantly greater high frequency (HF) power than healthy controls (HC) in all sleep stages (p<0.0001). SZs also exhibited significantly greater HF power than MDD patients in all sleep stages except wakefulness (W) (p<0.05). In all groups, gamma (35-45Hz) power was greater in W, decreased during slow wave sleep (SWS) and decreased further during rapid eye movement (REM). Beta 2 (20-35 Hz) power was greater in W and REM than in SWS. Only positive symptoms exhibited an association with HF power. Elevated HFA during sleep in unmedicated patients with SZ and MDD is associated with positive symptoms of illness. It is not clear how HFA would change in relation to clinical improvement, and further study is needed to clarify the association of HFA to the state/trait characteristics of SZ and MDD.

Cognitive Disorganization in Hippocampus: A Physiological Model of the Disorganization in Psychosis

“…These data add to the growing consensus that disturbed neural coordination at gamma (and beta) frequencies may underlie disorganized processing in different sensory modalities (Kwon et al, 1999;Spencer et al, 2003) during sleep and rest (Tekell et al, 2005). This predicts that the TTX-altered coactivity would occur at gamma frequencies if it reflects a schizophrenia-related phenomenon.…”

“…Furthermore, if the TTX-induced coactivity is related to the cognitive disorganization associated with disorganization in schizophrenia, one also expects the coactivity to manifest at the timescale of gamma because altered gamma is associated with schizophrenia (Kwon et al, 1999;Spencer et al, 2003) and correlates with disorganization symptoms (Spencer et al, 2004;Tekell et al, 2005).…”

Diagnose of Depression in Subjects with Sleep Disorders using Analysis of REM Sleep Electroencephalogram signals

“…The gamma activity in most of the case was higher in depressed subjects but has showed no significant differences in this study. These findings are in agreement with results of [15,19] which reported increase of beta and gamma activity in depressed subjects.…”

“…They also shown that the power density in the entire frequency range (0.25 to 25 Hz) exhibited a decreasing trend over the first three NREM/REM sleep cycles for both groups, but in each cycle depressed people had lower values than controls [6], although this result was breached in later years by Mendelson et al [7]. Tekell and colleagues in their work demonstrated increase of high frequencies activity in these patients [15]. It was shown that high frequencies and beta are greater in depressed women compared with depressed men, especially in right hemisphere [16].…”

Electrophysiological Deficits in Schizophrenia: Models and Mechanisms

“…Finally, lower levels of beta oscillatory activity have been observed in patients with schizophrenia (Rutter et al, 2009). In sleep studies, unmedicated patients had higher beta power at all stages of the sleep compared to healthy individuals (Tekell et al, 2005). Alternatively, deficient power and synchronization of evoked and induced EEG rhythms in the beta and gamma bands have frequently been reported (Clementz et al, 1997, Cho et al, 2006, Uhlhaas et al, 2006.…”