Maps of functional connectivity of Amygdala.

<p>(a) Decreased functional connectivity of left amygdala positive network in LOD compared with HC with a corrected threshold of <i>P</i><0.05, determined by Monte Carlo simulation. Cluster size is more than 119 voxels. (b) Increased functional connectivity of left amygdala negative network in LOD compared with HC with a corrected threshold of <i>P</i><0.05, determined by Monte Carlo simulation. Cluster size is more than 77 voxels. (c) Decreased functional connectivity of right amygdala negative network in LOD compared with HC with a corrected threshold of <i>P</i><0.05, determined by Monte Carlo simulation. Cluster size is more than 86 voxels. (d) − (e) Significant negative correlation between FC with right amygdala and VFT/DST. VFT: Verbal fluency test; DST: digit span test; <i>r</i> = spearman’s correlation coefficient.</p

Abnormal Functional Connectivity of Amygdala in Late-Onset Depression Was Associated with Cognitive Deficits

<div><p>Background</p><p>Major 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.</p><p>Methods and Results</p><p>A 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, <i>r</i> = −0.485, <i>P</i> = 0.022) and the digit span test (DST, <i>r</i> = −0.561, <i>P</i> = 0.007).</p><p>Conclusions</p><p>Our 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.</p></div

Demographic and neuropsychological data between LOD group and HC group.

<p>LOD: late-onset depression; HC: healthy controls; MMSE: Mini mental state exam; HAMA: Hamilton Anxiety Scale; HAMD: Hamilton Depression Scale; AVLT-delayed recall: Auditory Verbal Learning Test-delayed recall; SDMT: Symbol digit modalities test; DST: Digit span test-forward and backward; VFT: Verbal fluency test-animal and verb; TMT-A: Trail making test-A; TMT- B: Trail making test- B.</p>a<p>Independent-samples t-test.</p>b<p>Chi square test.</p>c<p>Analysis of covariance.</p

Significant Correlations between Neuropsychological Measurements and ReHo/FC with Amygdala in HC group.

<p>Note: this table only showed the significant correlations by Spearman's correlation. *: <i>P<</i>0.05.</p

Reduced ReHo in late onset depression compared with healthy controls with voxels with <i>P</i><0.05 and cluster size is more than 148 voxels, determined by Monte Carlo simulation,age, gender and education level as covariates.

<p>Reduced ReHo in late onset depression compared with healthy controls with voxels with <i>P</i><0.05 and cluster size is more than 148 voxels, determined by Monte Carlo simulation,age, gender and education level as covariates.</p

The result of one sample t-test in amygdala functional connectivity for LOD group and HC group.

<p><b>Note:</b> A corrected threshold of p<0.05 determined by Monte Carlo simulation was taken as meaning there was a significantly difference. Cluster size is more than 389 voxels. R  =  right; L  =  left; cluster size is in mm³.</p

Maps of functional connectivity with Amygdala in the results of one sample t-test.

<p>Resting state left amygdala FC pattern for (a) LOD group, (b) HC group. Resting state right amygdala FC pattern for (c) LOD group, (d) HC group. Corrected with Monte Carlo simulation, P<0.05, Cluster size is more than 119 voxels.</p

Reduced ReHo in LOD group compared with HC group.

<p><b>Note:</b> A corrected threshold of p<0.05 determined by Monte Carlo simulation was taken as meaning there was a significantly difference between groups. R  =  right; L  =  left; cluster size is in mm³.</p

Abnormal functional connectivity of bilateral amygdala in LOD group compared with HC group.

<p><b>Note:</b> A corrected threshold of p<0.05 determined by Monte Carlo simulation was taken as meaning there was a significantly difference between groups. R  =  right; L  =  left; cluster size is in mm³.</p

Altered Resting-State Brain Activity and Connectivity in Depressed Parkinson’s Disease

<div><p>Depressive symptoms are common in Parkinson’s disease (PD), but the neurophysiological mechanisms of depression in PD are poorly understood. The current study attempted to examine disrupted spontaneous local brain activities and functional connectivities that underlie the depression in PD. We recruited a total of 20 depressed PD patients (DPD), 40 non-depressed PD patients (NDPD) and 43 matched healthy controls (HC). All the subjects underwent neuropsychological tests and resting-state fMRI scanning. The between-group differences in the amplitude of low frequency fluctuations (ALFF) of BOLD signals were examined using post-hoc tests after the analysis of covariance. Compared with the NDPD and HC, the DPD group showed significantly increased ALFF in the left median cingulated cortex (MCC). The functional connectivity (FC) between left MCC and all the other voxels in the brain were then calculated. Compared with the HC and NDPD group, the DPD patients showed stronger FC between the left MCC and some of the major nodes of the default mode network (DMN), including the post cingulated cortex/precuneus, medial prefrontal cortex, inferior frontal gyrus, and cerebellum. Correlation analysis revealed that both the ALFF values in the left MCC and the FC between the left MCC and the nodes of DMN were significantly correlated with the Hamilton Depression Rating Scale score. Moreover, higher local activities in the left MCC were associated with increased functional connections between the MCC and the nodes of DMN in PD. These abnormal activities and connectivities of the limbic-cortical circuit may indicate impaired high-order cortical control or uncontrol of negative mood in DPD, which suggested a possible neural mechanism of the depression in PD.</p></div