Hippocampal resting‐state connectivity is associated with posterior‐cortical cognitive impairment in Parkinson's disease

Abstract

Abstract Aim Frontal and posterior‐cortical cognitive subtypes in Parkinson's disease (PD) present with executive/attention and memory/visuospatial deficits, respectively. As the posterior‐cortical subtype is predicted to progress rapidly toward dementia, the present study aimed to explore biological markers of this group using resting‐state functional magnetic resonance imaging (rs‐fMRI). Methods K‐means cluster analysis delineated subtypes (cognitively intact, frontal, posterior‐cortical, and globally impaired) among 85 people with PD. A subset of PD participants (N = 42) and 20 healthy controls (HCs) underwent rs‐fMRI. Connectivity of bilateral hippocampi with regions of interest was compared between posterior‐cortical, cognitively intact, and HC participants using seed‐based analysis, controlling for age. Exploratory correlations were performed between areas of interest from the group analysis and a series of cognitive tests. Results The posterior‐cortical subtype (N = 19) showed weaker connectivity between the left hippocampus and right anterior temporal fusiform cortex compared to the cognitively intact (N = 11) group, p‐false discovery rate (FDR) = .01, and weaker connectivity between bilateral hippocampi and most fusiform regions compared to HCs (N = 20). No differences were found between HCs and cognitively intact PD. Exploratory analyses revealed strongest associations between connectivity of the right anterior temporal fusiform cortex and left hippocampus with category fluency (p‐FDR = .01). Conclusion Results suggest that weakened connectivity between the hippocampus and fusiform region is a unique characteristic of posterior‐cortical cognitive deficits in PD. Further exploration of hippocampal and fusiform functional integrity as a marker of cognitive decline in PD is warranted.

Keywords

• cognitive impairment
• hippocampus
• Parkinson's disease
• resting‐state FMRI