Abstract
BackgroundMajor depressive disorder (MDD) is associated with decreased function of cortico-limbic circuits, which play important roles in the pathogenesis of MDD. Abnormal functional connectivity (FC) with the amygdala, which is involved in cortico-limbic circuits, has also been observed in MDD. However, little is known about connectivity alterations in late-onset depression (LOD) or whether disrupted connectivity is correlated with cognitive impairment in LOD.Methods and ResultsA total of twenty-two LOD patients and twenty-two matched healthy controls (HC) underwent neuropsychological tests and resting state functional magnetic resonance imaging (rs-fMRI). Regional homogeneity (ReHo) and FC with bilateral amygdala seeds were used to analyze blood oxygen level-dependent fMRI data between two groups. Compared with HC, LOD patients showed decreased ReHo in the right middle frontal gyrus and left superior frontal gyrus. In the LOD group, the left amygdala had decreased FC with the right middle frontal gyrus and the left superior frontal gyrus in the amygdala positive network, and it had increased FC with the right post-central gyrus in the amygdala negative network. However, significantly reduced FC with the right amygdala was observed in the right middle occipital gyrus in the amygdala negative network. Further correlative analyses revealed that decreased FC between the amygdala and the right middle occipital gyrus was negatively correlated with the verbal fluency test (VFT, r = −0.485, P = 0.022) and the digit span test (DST, r = −0.561, P = 0.007).ConclusionsOur findings of reduced activity of the prefrontal gyrus and abnormal FC with the bilateral amygdala may be key markers of cognitive dysfunction in LOD patients.
Highlights
Late-onset depression (LOD), which refers to depressive syndromes as defined in the American Psychiatric Association’s Diagnostic and Statistical Manual (DSM-IV), is an important public health problem due to its high prevalence of 6.5% to 9% [123]
Neuropsychological results Compared with healthy controls (HC), late-onset depression (LOD) patients displayed comprehensive deficits in cognitive performance, including language, attention, executive and memory functions
The correlative analyses in the LOD group results showed that the Hamilton Depression Rating Scale (HAMD) total score had no correlations with cognitive functions, but the Hamilton Anxiety Rating Scale (HAMA) total score was negatively correlated with Auditory Verbal Learning Test (AVLT)-delayed recall (r = 20.440, P = 0.041) and HAMD score (r = 0.799, P = 0.000)
Summary
Late-onset depression (LOD), which refers to depressive syndromes as defined in the American Psychiatric Association’s Diagnostic and Statistical Manual (DSM-IV), is an important public health problem due to its high prevalence of 6.5% to 9% [123]. LOD is often associated with cognitive impairment, so it is often referred to as either a pseudodementia syndrome or a prodrome of dementia [428]. Episodic memory and executive function are much worse in LOD patients than in healthy controls [9]. This cognitive impairment persists even after the remission of mood symptoms [10]. Major depressive disorder (MDD) is associated with decreased function of cortico-limbic circuits, which play important roles in the pathogenesis of MDD. Little is known about connectivity alterations in late-onset depression (LOD) or whether disrupted connectivity is correlated with cognitive impairment in LOD
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