Disentangling the role of working memory in Parkinson's disease

Abstract

Parkinson’s disease (PD) is a neurodegenerative disorder characterised by motor symptoms but also associated with decline in cognitive status and psychiatric well-being. Working memory (WM) risk is particularly prominent due to the fronto-striatal degeneration associated with PD, but the nature of WM problems remains ambiguous. In order to establish a thorough understanding of WM and to generate methods for monitoring decline, mediating factors need to be examined. The aim of this study was to assess the connections between WM task performance, self-rated cognitive deficits, and affective symptoms in PD, as compared to healthy controls. The participants of this study were 52 cognitively well-preserved PD patients and 54 healthy controls. All participants completed a home-based online assessment, consisting of tasks tapping the WM subdomains of 1) selective updating, 2) continuous monitoring, and 3) maintenance, and of questionnaires capturing cognition and mood. The data was analysed using structural equation models, allowing for the investigation of predictive and correlative relationships between latent factors. Our findings suggest that in cognitively well-preserved PD patients, selective updating is the WM subdomain most sensitive to impairments. WM performance was not linked with either self-rated cognitive deficits or affective symptoms, but these self-rating factors were correlated with each other. Hence, affective symptoms may worsen the subjective perception of cognitive deficits. Moreover, WM deficits appear to be associated with the overall cognitive decline in PD, rather than constitute an isolated symptom or stem directly from the disease mechanism. In our experience, online testing was found to be feasible, opening novel means to monitor the cognitive status of PD patients in a cost-effective and user-friendly manner.