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

Abstract

Background Although people with schizophrenia (PSZ) frequently exhibit reduced working memory capacity relative to healthy comparison subjects (HCS), the mechanisms that underlie this impairment are not yet known. 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 The electroencephalogram (EEG) 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 Overall, we found that PSZ had significantly reduced alpha and beta-band suppression during the delay interval compared to HCS, and that these significant differences emerged early (100-200 ms after the 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.

Functional Dissociation of Confident and Not-Confident Errors in the Spatial Delayed Response Task Demonstrates Impairments in Working Memory Encoding and Maintenance in Schizophrenia

“…The present findings of impairments of WM in schizophrenia at the level of encoding and maintenance processes are consistent with findings from electrophysiological( 33 – 39 , 62 ) and event-related fMRI studies ( 17 , 18 , 27 , 38 , 40 , 41 , 55 ) that explicitly examined WM encoding-related and WM maintenance-related neural abnormalities in schizophrenia and in unaffected first-degree relatives of PSZ ( 27 , 40 ). These studies suggest that a PFC dysfunction—which has been discussed as a core mechanism underlying WM deficits in schizophrenia ( 1 , 5 )—contribute not only to impaired WM maintenance but also to impaired WM encoding.…”

Mnemonic and attentional roles for states of attenuated alpha oscillations in perceptual working memory: a review

“…This yielded an unambiguous pattern of results: during retention of visual sequences, alpha (as well as beta) oscillations were almost exclusively attenuated in visual brain areas, whereas during retention of somatosensory sequences, this was the case in somatosensory brain areas (van Ede et al ., ). In both modalities, these WM related attenuations of alpha and beta oscillations scaled with load (see also Fukuda et al ., ; Erickson et al ., ). These results could not simply be accounted for by differences in sensory processing, as sensory stimulation was equated between control and WM trials, between visual and somatosensory WM trials and between trials with different WM loads (van Ede et al ., , for details).…”

“…However, the sign of these modulations is opposite. When participants engage in verbal retention (even when information is encoded visually, as in Jensen et al ., ; Tuladhar et al ., ), the amplitude of posterior (putatively visual) alpha increases with load, whereas when they engage in visual retention (as argued in van Ede et al ., ), alpha amplitude now decreases with load (for more demonstrations of alpha attenuation during WM see also: Medendorp et al ., ; Fukuda et al ., ; Erickson et al ., ). The direction of modulation thus appears to be highly dependent on the nature of the memoranda (as well as the source of the alpha oscillations under consideration; as in e.g.…”

Alpha‐band desynchronization reflects memory‐specific processes during visual change detection

“…A number of studies have reported robust event-related desynchronization of alpha and beta (α/β-ERD) following the onset of a visual array of stimuli to be memorized, which is associated with successful recall for those items among healthy individuals at test (Astrand, 2018;Bashivan, Bidelman, & Yeasin, 2014;Chen, Chen, Kuang, & Huang, 2015;Foster, Sutterer, Serences, Vogel, & Awh, 2016;Fukuda, Mance, & Vogel, 2015;Pavlov & Kotchoubey, 2017;Sauseng et al, 2009;van Dijk, van der Werf, Mazaheri, Medendorp, & Jensen, 2010;Zammit, Falzon, Camilleri, & Muscat, 2018). Furthermore, disrupted α/β-ERD has been observed in clinical samples with known WM capacity impairments such as schizophrenia and attention deficit hyperactivity disorder (Erickson, Albrecht, Robinson, Luck, & Gold, 2017;Lenartowicz, Mazaheri, Jensen, & Loo, 2018). Taken together, α/β-ERD during memory formation and maintenance appears to be directly linked to the quantity or quality of those representations, and failure of this mechanism constrains WM capacity in certain forms of psychopathology.…”