Structural Neuroimaging of Concomitant Depressive Symptoms in Amnestic Mild Cognitive Impairment: A Pilot Study

Abstract

Late-life depression (LLD) and amnestic mild cognitive impairment (aMCI) can both denote prodromal Alzheimer’s disease. While the two concepts share common clinical features, differential diagnosis between them is crucial. The objective of this pilot study was to explore differences in terms of the hippocampal (HC) and entorhinal cortex (EC) volume reduction between LLD and aMCI patients with (aMCI/D+ group) or without (aMCI group) depressive symptoms. Six LLD, 6 aMCI, and 6 aMCI/D+ participants were assessed using a structural magnetic resonance imaging protocol. Manual segmentation of HC and EC was carried out. The results of volumetric comparisons suggest that the HC was larger in aMCI/D+ and LLD subjects compared to aMCI participants. The left EC mean volume was slightly lower in aMCI/D+ subjects. Power analyses revealed that 36 participants per group would suffice to confirm these findings. Overall, these pilot findings suggest that aMCI can be distinguished from LLD based on cerebral atrophy measures, and that HC and EC atrophy in aMCI varies according to the presence or absence of depressive symptoms.

Memory for emotional images differs according to the presence of depressive symptoms in individuals at risk for dementia

“…Indeed, although depressed and non-depressed aMCI participants in this study were comparable in terms of their memory performance on clinical tasks, and indeed recalled comparable quantities of items on the experimental task, the quality of the information remembered differed significantly. In addition, considering that behavior is an indicator of brain vulnerability, results from this study add to those of previous work (Brunet et al, 2011;Morin et al, 2012;Callahan et al, 2014Callahan et al, , 2016 to imply the likely existence of distinct neurobiological or neurofunctional manifestations in aMCI, aMCI/D+, and LLD. This necessitates further investigation using imaging measures, but we might speculate about plausible mechanisms by which depressive symptoms affect emotional memory.…”

“…It is possible that performance in participants with aMCI/D+ is the result of neurobiological changes, potentially involving the hippocampus and/or the amygdala. Hippocampal atrophy has been associated with both aMCI and depression, independently (Morin et al, 2012) and correlates with recall of emotional pictures (Schultz et al, 2009). Similarly, amygdalar lesions are known to be present in early AD (Klein-Koerkamp et al, 2012) and in depressed seniors (Burke et al, 2011), and are thought to contribute to the disruption of emotional processes involved in emotional memory enhancement (Kensinger and Leclerc, 2009).…”

“…Of note, individuals with aMCI/D+ could not meet DSM-IV-TR mood disorder criteria because their impaired social and/or occupational functioning was considered to be primarily a result of cognitive decline; in contrast, functional impairment was considered to be primarily a result of depressive symptoms in LLD participants, therefore meeting DSM-IV-TR mood disorder criteria. Although some studies have examined the relationship between depression and cognition using a continuous measure of GDS, the use of a splitting method here was based on the hypothesis that aMCI and aMCI/D+ are two distinct groups, phenotypically and perhaps also etiologically (Hudon et al, 2008;Brunet et al, 2011;Morin et al, 2012;Callahan et al, 2014Callahan et al, , 2016.…”

“…Only very recently have studies begun to examine how the cognitive profile of comorbid aMCI and depressive symptoms (aMCI/D+) relates to that of aMCI and LLD separately. This question bears considerable importance, because different cognitive profiles would suggest the existence of distinct neuropathological manifestations; preliminary results from a neuroimaging study indeed suggest different patterns of brain atrophy in aMCI, aMCI/D+, and LLD samples (Morin et al, 2012, but see Lee et al, 2012). Furthermore, there is evidence indicating that the progression rate to dementia is significantly higher in aMCI/D+ than in aMCI (e.g.…”

Differences in Prefrontal, Limbic, and White Matter Lesion Volumes According to Cognitive Status in Elderly Patients with First-Onset Subsyndromal Depression

“…Few studies have explored brain structural changes in a depressed, cognitively impaired geriatric population; these studies reported that late-life depression was not significantly associated with lobar gray or white matter atrophy [43] but, it was significantly associated with hippocampus and left entorhinal cortex [44] . The mechanisms underlying depressive symptoms in cognitively impaired patients are unclear.…”