Schizophrenia Spectrum and Psychotic Disorders

Deficits of Short-Term Memory Among Individuals With First-Episode Schizophrenia During Visual Tasks

Jessica Nye, PhD
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This study investigates whether contralateral delay activity occurs early in schizophrenia, possibly indicating that visual short-term memory deficits are a core feature of the disorder.

Researchers from the University of Pittsburgh School of Medicine found that dysfunctional working memory maintenance was a central component of schizophrenia and may be a possible therapeutic target. These results were published in the Journal of Psychiatric Research.

Participants for this study were either healthy controls (n=38) or those experiencing first-episode schizophrenia (FESz; n=40). Participants were assessed by neuropsychological scores and for contralateral delay activity (CDA) during low and high memory load visual tasks.

Patients with FESz and controls were well balanced for demographics, but differed significantly concerning years of education (P =.047), and MATRICS Consensus Cognitive Battery (MCCB) processing speed (P =.001), attention (P =.006), verbal learning (P =.028), reasoning (P =.043), social cognition (P =.003), and total MCCB scores (P <.001).

In general, as MCCB scores increased so did the difference in memory capacity among both controls (r=0.51; P =.005) and patients (r=0.40; P =.041). Similarly, as MCCB scores increased so did the difference in CDA dependent on the source-level (FESz: r=0.46; P =.018 vs controls: r=0.56; P =.005). Conversely, greater positive symptom severity scores were indicative of reduced differences in memory capacity (r=-0.49; P =.042) and source-level CDA (r=-0.45; P =.043) among patients with FESz.

Patients with FESz had a lower capacity for visual short-term memory compared with controls (F[1,50]=4.6; P =.037). This variance was driven more by differences between groups for high load (FESz: mean, 1.75±0.72 vs controls: mean, 2.11±0.54; P =.040) than for low load (FESz: mean, 0.85±0.20 vs controls: mean, 0.93±0.12; P =.094).

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Electroencephalogram-measured CDA showed no major difference between groups; however, CDA was larger for high rather than for low memory load (F[1,50]=7.4; P =.009). The investigators observed a between-group interaction in which controls exhibited larger CDA during high load trials (t[50]=2.09; P =.042) and for low load trials among patients with FESz (t[50 =-2.09; P =.042). No significant effect of memory load was observed among those with FESz (P =.19), but the effect of memory load was observed among controls (P =.009).

Reaction times among patients with FESz were correlated with source-level CDA for the different memory load trials in which greater differences of reaction times were related with a greater source-level difference in CDA (r=0.40; P =.041).

A limitation of this study was the sample size. Several measured effects did not reach statistical significance, which may have been a byproduct of these underpowered data.

The study authors concluded that individuals experiencing FESz were found to exhibit reduced modulation of lateralized parietal activity. It remained unclear whether this behavior was a downstream result of general brain dysfunction. Further studies are needed to determine whether these effects are related to dysfunction of executive symptoms or due to inefficient communication between executive and representational brain systems. Nonetheless, these data indicated that non-invasive brain stimulation or cognitive training may be a possible therapeutic option for patients with FESz.

Reference

Coffman BA, Murphy TK, Haas G, et al. Lateralized evoked responses in parietal cortex demonstrate visual short-term memory deficits in first-episode schizophrenia. J Psychiatr Res. 2020;130:292-299. doi: 10.1016/j.jpsychires.2020.07.036.