The Effects of Late-Onset Depression on Brain Activity During an Episodic Memory Task

Late-onset depression (LOD) has been implicated in irreversible cognitive decline, potentially mirroring early Alzheimer's Disease (AD) pathology. This study aimed to investigate brain activity differences during an episodic memory (EM) task in LOD patients compared to healthy controls (HC).

We recruited 15 LOD patients and 13 HC matched for age and gender. Participants completed a face-name association task during functional magnetic resonance imaging (fMRI) focusing on both the encoding and retrieval phases of EM.

The statistical contrast between the groups revealed that the HC group showed increased activity in the left visual association cortex (VAC) and left caudate compared to the LOD group during the encoding task. During the face recognition task, the HC group showed increased activity in the right caudate, and during the name recognition task, they showed increased activity in the right frontal eye field (FEF) compared to the LOD group.

The differences observed between the HC and LOD groups in the VAC, caudate, and FEF suggest early changes in maintaining attention, goal-directed learning, EM formation, and coordination of information from storage to retrieval before apparent impairment develops in LOD. Although we did not find statistically significant activations in areas linked to increased vulnerability to AD, our findings of hypoactivation in regions responsible for visual processing and attentional orienting in LOD patients are consistent with hypoactivation patterns observed in AD patients in previous research. These results enhance our understanding of the neural mechanisms underlying memory impairments in LOD and their potential overlap with AD pathology.