Impaired odor recognition memory in Parkinson's disease linked to absent functional hippocampal asymmetry

Odor recognition memory (ORM) combines olfaction and episodic memory, both linked to dementia and impaired in Parkinson's Disease (PD). Measuring ORM may indicate early PD dementia and aid in selecting device-aided Parkinson therapy. This study investigates ORM capacity and hippocampal dynamic functional connectivity in PD. Thirty-one PD participants and 31 healthy controls (HC) underwent functional MRI during an ORM task. Co-activation pattern analysis identified active hippocampal networks. The PD group showed impaired ORM and a sequence of four activated hippocampal networks. The fourth network, involving the dorsal Attention Network (dAN), had fewer and shorter expressions during correct ORM responses in PD compared with HC. Hippocampal functional asymmetry was observed in HC but not in PD. These findings suggest that impaired ORM in PD is linked to reduced hippocampal functional asymmetry. Future research should explore differences in functional dynamics of odor memory-related brain regions in PD patients with and without cognitive decline.