S8. Alpha Desynchronization Impairment in People With Schizophrenia During Working Memory Reflects Abnormality at the Consolidation Stage of Memory Formation
Year: 2019
Type: article
Abstract: Although people with schizophrenia (PSZ) exhibit robust and reliable reductions in visual working memory capacity compared to healthy control subjects (HCS), the mechanisms that give rise to this impairment are not yet known. Recently, we and others have reported evidence that event-related desynchronization within the alpha frequency band of the electroencephalogram (9–13 Hz; alpha-ERD) during the delay period of a visual working memory task is significantly associated with working memory capacity among HCS (Erickson et al., 2017). Importantly, we found that this signal is robustly impaired in PSZ; as a group, they exhibit substantially reduced alpha-ERD during working memory formation and maintenance (Cohen’s d > 1.0). These observations implicate alpha-ERD impairment as a primary mechanism by which working memory is constrained in PSZ. However, it is not yet known at which stage of visual memory formation alpha-ERD emerge in PSZ. There are several sub-processes that support successful working memory, including perception, attention, consolidation, maintenance, and response selection. Impairment at any of these stages could be reflected in reduced alpha-ERD and lower working memory capacity estimates, but a typical working memory paradigm cannot distinguish between these stages of memory formation. In the present study, we examined alpha-ERD in 8 PSZ and 8 HCS in three EEG tasks designed to isolate the following sub-processes of working memory, separately: perception (participants passively view a sample array), attention (participants view and attend to the sample array in search of a target color, but are not required to memorize the colors), and memory consolidation/maintenance (participants view, attend, and memorize colors from sample array). EEG was time-locked to the onset of the sample array in each of the three conditions, and time-frequency analysis was performed by convolving a Hanning-tapered three-cycle Morlet wavelet with the EEG from each channel. Power in the alpha frequency band (9–13 Hz) was then baseline corrected to the proportional change in post-stimulus power relative to the 1500 ms before the onset of the sample array on a logarithmic scale (dB). Consistent with previous findings (Erickson et al., in preparation), we observed that alpha-ERD was significantly larger when participants were asked to remember the sample array colors compared to when they were asked to passively perceive or attend to the items in both groups (F = 3.85; p < 0.05). Additionally, we also find preliminary evidence for a replication of previous findings that PSZ have reduced alpha-ERD in the memory condition compared to HCS (p = 0.06; Cohen’s d = 1.02). Importantly, however, PSZ exhibit normal alpha-ERD in the perception and attention task conditions (p’s = 0.84 and 0.12, respectively), indicating a specificity of alpha-ERD impairment to task conditions that require memory consolidation and storage. Taken together, these results suggest that the alpha-ERD impairment observed during visual working memory tasks do not reflect failure at early visual stages of perception and attention. Rather, it appears that alpha-ERD impairments only emerge during consolidation. Such findings have important implications for future treatment development aimed to remediate working memory capacity in PSZ.
Source: Schizophrenia Bulletin
Authors: Molly Erickson, Dillon Smith, Laura Crespo, Steven Silverstein
Institution: Rutgers, The State University of New Jersey
Language: English
Subfield: Psychiatry and Mental health
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W2937180623