Transdiagnostic comparison of visual working memory capacity in bipolar disorder and schizophrenia

Abstract

Background Impaired working memory is a core cognitive deficit in both bipolar disorder and schizophrenia. Its study might yield crucial insights into the underpinnings of both disorders on the cognitive and neurophysiological level. Visual working memory capacity is a particularly promising construct for such translational studies. However, it has not yet been investigated across the full spectrum of both disorders. The aim of our study was to compare the degree of reductions of visual working memory capacity in patients with bipolar disorder (PBD) and patients with schizophrenia (PSZ) using a paradigm well established in cognitive neuroscience. Methods 62 PBD, 64 PSZ, and 70 healthy controls (HC) completed a canonical visual change detection task. Participants had to encode the color of four circles and indicate after a short delay whether the color of one of the circles had changed or not. We estimated working memory capacity using Pashler’s K. Results Working memory capacity was significantly reduced in both PBD and PSZ compared to HC. We observed a small effect size (r = .202) for the difference between HC and PBD and a medium effect size (r = .370) for the difference between HC and PSZ. Working memory capacity in PSZ was also significantly reduced compared to PBD with a small effect size (r = .201). Thus, PBD showed an intermediate level of impairment. Conclusions These findings provide evidence for a gradient of reduced working memory capacity in bipolar disorder and schizophrenia, with PSZ showing the strongest degree of impairment. This underscores the importance of disturbed information processing for both bipolar disorder and schizophrenia. Our results are compatible with the cognitive manifestation of a neurodevelopmental gradient affecting bipolar disorder to a lesser degree than schizophrenia. They also highlight the relevance of visual working memory capacity for the development of both behavior- and brain-based transdiagnostic biomarkers.

External Cues Improve Visual Working Memory Encoding in the Presence of Salient Distractors in Schizophrenia

“…To assess the relationship between the ability to prioritize task-relevant information and WM capacity, we correlated the effectiveness of attentional prioritization (Cowan's K for target trials minus Cowan's K for catch trials) in each participant across all four conditions with an independent estimate of VWM capacity derived from a 60-trial canonical change detection task (33). For 200 ms, Participants viewed an array of four colored circles, which were spaced equally apart on an imaginary circle around a central fixation cross (Figure S1).…”

“…To assess the relationship between the ability to prioritize relevant information and VWM capacity, we correlated the efficiency of attentional prioritization (Cowan's K for target trials minus Cowan's K for catch trials) using Spearman correlations in each group across all four conditions with an independent estimate of VWM capacity (Pashler's K, (Pashler, 1988)) derived from our canonical visual change detection task (Barnes-Scheufler et al, 2021).…”

Impaired Visuospatial Working Memory but Preserved Attentional Control in Bipolar Disorder

“…We also employed a 60-trial canonical visual change detection task (Barnes-Scheufler et al, 2021) to obtain an independent estimate of VWM capacity (see supplementary materials).…”

“…Similar levels of WM impairment have been observed in both type I and type II BD (Bora, 2018; Bora, Yücel, Pantelis, & Berk, 2011; Mayer & Park, 2012), but PBD with a history of psychosis appear to be more affected than other PBD (Bora, 2018). WM capacity is reduced even in euthymic PBD (Barnes-Scheufler et al, 2021; Gold et al, 2018; Mayer & Park, 2012). Importantly, functional neuroimaging studies indicate disturbances during WM encoding in areas closely involved in both WM and attention (Huang et al, 2019; Linden et al, 2003; Mayer et al, 2007; McKenna, Sutherland, Legenkaya, & Eyler, 2014).…”

“…Both working memory (WM) and attention are regarded as central cognitive domains for transdiagnostic studies of impaired information processing (Insel et al, 2010). Specifically, WM dysfunction is a crucial deficit in both PBD and schizophrenia (Barch & Smith, 2008; Glahn et al, 2006), with stronger impairment observed in schizophrenia (Barnes-Scheufler et al, 2021). It remains the most consistently reported cognitive deficit in PBD and correlates most strongly with functional outcome (Keramatian, Torres, & Yatham, 2021), making it a key target for pro-cognitive interventions in PBD (Miskowiak et al, 2018).…”