Introduction. In dementia with Lewy bodies (DLB), mutations in the GBA gene are associated with a more severe cognitive phenotype. In basic science, event-related oscillations have traditionally been used to explore the neurophysiological underpinnings of various aspects of cognitive performance. Here, we aimed to compare event-related oscillations in DLB patients who are carriers and non-carriers of GBA mutations.
Method. EEG was recorded during a visual oddball task in eight clinically diagnosed Ashkenazi Jewish DLB patients with the N370S mutation in the GBA gene (GBA-DLB) and eleven DLB non-carriers. The time-frequency power and inter-trial phase coherence were calculated from the Morlet wavelet convolution from the Fz electrode.
Results. Task performance and cognitive assessments were comparable between groups. While the within-non-GBA-DLB group analysis revealed a significant increase relative to the baseline in the delta-band power (p=0.01, Cohen's d=1.0), the within-GBA-DLB-group analysis did not detect any event-related power change. In contrast, both subgroups showed an increase relative to the baseline in the delta and theta bands inter-trial phase coherence (all p<0.03, d>1.3). The between-group analysis revealed that event-related power - but not coherence - was lower in GBA-DLB compared to non-carriers in the delta band (p=0.04, d=-0.9).
Conclusions. GBA-DLB patients showed decreased delta-band power compared to non-carriers despite the similar cognitive performance, whereas inter-trial phase coherence was comparable in both groups. These findings suggest that in carriers, preserved inter-trial phase coherence possibly compensates for the impaired power by eliciting the appropriate functional configuration needed for stimulus processing and task performance.