Impaired Suppression of Delay-Period Alpha and Beta Is Associated With Impaired Working Memory in Schizophrenia

BACKGROUND: Although patients with schizophrenia (PSZ) frequently exhibit reduced working memory capacity relative to healthy control subjects (HCS), the mechanisms that underlie this impairment are unknown. The present study aimed to assess one putative mechanism: impaired suppression of alpha and beta frequency bands during the delay period of a visual working memory task. METHODS: An electroencephalogram was recorded from 30 PSZ and 31 HCS while they completed a change detection task in which they were required to remember a briefly presented array of colored squares over an 1800-ms delay interval. RESULTS: PSZ had significantly reduced alpha- and beta-band suppression during the delay interval compared with HCS, and these significant differences emerged early (100-200 ms after onset of the memory array). Furthermore, the magnitude of suppression was significantly associated with task performance across both groups. Finally, the magnitude of suppression in alpha and beta frequency bands was significantly associated with a range of cognitive measures among HCS, but not PSZ. CONCLUSIONS: These results implicate impaired alpha/beta suppression during the consolidation period of working memory tasks as a promising neural mechanism that constrains capacity in PSZ.