EEG markers of cognitive performance in bipolar disorder - A systematic review

People with bipolar disorder (BD) may experience impairing cognitive deficits, even in remission. Electroencephalographic (EEG) measures can depict neurophysiological activity with high temporal resolution. They could therefore be an adequate method to pinpoint the cognitive impairments in BD, facilitating understanding of when exactly the cognitive processing is disrupted and what neurophysiological systems are involved. In the absence of a previous literature examination, this systematic review aimed to synthesize the evidence of associations between EEG and cognitive measures to identify electrophysiological markers of cognitive performance in BD.

A systematic search across PubMed, EMBASE, APA PsycInfo and Cochrane Library until November 2023 was undertaken to identify studies in which a direct correlation between any continuous EEG measure and any continuous cognitive measure in participants with BD was reported. A narrative synthesis approach was used to present the identified correlations, across five cognitive (attention and processing speed, working memory, episodic memory, executive function, and intellectual capacity) and four EEG domains (event-related potentials (ERP), spectral, connectivity and other measures).

A total of 16 articles describing 15 studies were included in the review. Six studies identified significant correlations. Most significant correlations were reported between ERP measures and attention and processing speed performance, several between ERP measures and executive functioning and one within the working memory and the intellectual capacity domain respectively. However, most of the identified significant correlations were conflicting within (different measures or mood states) and across studies with no consistent significant correlation across studies. The majority of identified correlations were non-significant.

As yet no robust EEG markers of cognitive performance in people with BD are known. This review highlights the heterogeneity in measures and participant characteristics between studies and the need for standardization. Further studies with homogeneous methods and participant groups may help to establish consistent associations.