Exploring the discrepancy of hippocampal subfield vulnerability and connectivity pattern between cognitive decline in PD and MCI patients

Motivation: Different vulnerabilities of hippocampal subfields in PD and MCI have been reported. Goal(s): To explore the discrepancy of hippocampal subfield atrophy and its FC pattern in HC, PDNCI, PDMCI, and MCI patients. Approach: Volume of hippocampal subfields, and FC between impaired subfields and cortical regions were calculated to assess group differences. Results: PD groups had reduced volumes in CA2/3, CA4, and GC-DG subfields and increased FC in the visual network.MCI group exhibited decreased right CA4 volume and increased FC in the widespread visual network.PDMCI displayed enhanced FC in the DMN compared to PDNCI and decreased FC in the visual network relative to MCI. Impact: As cognitive decline advances in PD, FC alterations are prominent between the GC-DG+CA4 subfield and the DMN. Smaller hippocampal subfield and its widespread FC abnormalities in MCI relative to PDMCI may underscore the different progression mechanisms of the two diseases.