Association between segmental alterations of white matter bundles and cognitive performance in first-episode, treatment-naïve young adults with major depressive disorder.

BACKGROUND: Cumulative evidence has consistently shown that white matter (WM) disruption is associated with cognitive decline in geriatric depression. However, limited research has been conducted on the correlation between these lesions and cognitive performance in untreated young adults with major depressive disorder (MDD), particularly with the specific segmental alterations of the fibers. METHOD: Diffusion tensor images were performed on 60 first-episode, treatment-naïve young adult patients with MDD and 54 matched healthy controls (HCs). Automated fiber quantification was applied to calculate the tract profiles of fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD) to evaluate the WM microstructural organization. Correlation analysis was performed to find the associations between the diffusion properties and cognitive performance. RESULTS: Compared with HCs, patients with MDD exhibited predominantly different diffusion properties in bilateral uncinate fasciculus (UF), corticospinal tracts (CSTs), left superior longitudinal fasciculus and anterior thalamic radiation. The FA of the temporal cortex portion of right UF was positively correlated with working memory. The MD of the temporal component of left UF was negatively correlated with working memory and positively correlated with symptom severity. Additionally, a positive correlation between the MD of left CST and the psychomotor speed, negative correlation between the MD of left CST and the executive functions and complex attentional processes were observed. CONCLUSIONS: Our study validated the alterations in spatial localization of WM microstructure and its correlations with cognitive performance in first-episode, treatment-naïve young adults with MDD. This study added to the knowledge of the neuropathological basis of MDD.

Executive function deficit in betel quid-dependence: Evidence from functional and effective connectivity of executive control network.

Betel quid (BQ) ranks fourth in global self-administered psychoactive agents, after caffeine, alcohol and nicotine, with 600 million consumers. Patients with BQ dependence (BQD) disorder demonstrate deficits in executive function. However, the neural correlates of the resting-state executive control network (ECN) and BQD-related pathopsychological characteristics still remain unclear. The present study aimed to assess the functional and effective connectivity of the ECN using resting-state functional magnetic resonance imaging (rs-fMRI). Fifty-five BQD individuals and 54 healthy controls (HCs) were recruited in this study. The executive function of all participants was tested by three tasks. Independent component and Granger causal analysis were employed to investigate the functional connectivity within ECN and ECN-related directional effective connectivity, separately. Behavioural results suggested a marked deficit of executive function in BQD individuals. Compared with HCs, BQD individuals showed overall weaker functional connectivity in the ECN, mainly including dorsolateral prefrontal cortex (DLPFC), inferior parietal lobule (IPL) and middle frontal gyrus (MFG). We observed decreased outflow of information from the right DLPFC and IPL to the precentral/pre-supplement motor area (SMA) and increased outflow of information from the MFG to the middle occipital gyrus in BQD individuals. Correlation analysis revealed that the effective connectivity from IPL to precentral/pre-SMA was negatively correlated to the BQD scales in BQD individuals. Our findings revealed impaired executive function, functional connectivity of the ECN and causal interaction between networks in patients with BQD. These results could potentially direct future targets for the prevention and intervention of BQD.

Decreased functional connectivity in salience network is associated with symptom severity in betel quid-dependent chewers.

BACKGROUND: Betel quid (BQ) is the fourth most popular psychoactive agent worldwide. Neuroimaging studies have showed that substance-addicted individuals including alcohol, heroin, nicotine and other addictive substance exhibit altered activity patterns of the salience network (SN). However, no study has yet investigated the neural correlates of the resting-state SN and BQ dependence (BQD)-related physiopathological characteristics. METHODS: Thirty-two BQ-dependent (BQD) chewers and 32 healthy controls were recruited to participate in this study. Resting-state functional magnetic resonance imaging (fMRI) data were analysed by independent component analysis (ICA). RESULTS: BQD chewers exhibited decreased functional connectivity in bilateral insula, anterior cingulate cortex (ACC), medial superior frontal gyrus (MSFG) and inferior orbital frontal gyrus (IOFG) [false discovery rate (FDR) correction, p < 0.05]. In the BQD group, the decreased functional connectivity in left ACC correlated negatively with BQDS (BQD Scale) and the duration of BQ. CONCLUSIONS: We reported decreased functional connectivity in resting-state SN of BQD individuals. The decreased functional connectivity in left ACC correlated negatively with BQDS and the duration of BQ. Our findings provided evidence for the importance of the SN in the pathophysiology of BQD and indicated that the SN dysfunction might provide a potential mechanism in BQD development.

Regional metabolic heterogeneity in anterior cingulate cortex in major depressive disorder: A multi-voxel 1H magnetic resonance spectroscopy study.

BACKGROUND: Previous studies have shown major depressive disorder (MDD) is associated with altered neuro-metabolites in the anterior cingulate cortex (ACC). However, the regional metabolic heterogeneity in the ACC in individuals with MDD remains unclear. METHODS: We recruited 59 first-episode, treatment-naive young adults with MDD and 50 healthy controls who underwent multi-voxel 1H-MRS scanning at 3 T (Tesla) with voxels placed in the ACC, which was divided into two subregions, pregenual ACC (pACC) and anterior midcingulate cortex (aMCC). Between and within-subjects metabolite concentration variations were analyzed with SPSS. RESULTS: Compared with control subjects, patients with MDD exhibited higher glutamate (Glu) and glutamine (Gln) levels in the pACC and higher myo-inositol (MI) level in the aMCC. We observed higher Glu and Gln levels and lower N-acetyl-aspartate (NAA) level in the pACC than those in the aMCC in both MDD and healthy control (HC) groups. More importantly, the metabolite concentration gradients of Glu, Gln and NAA were more pronounced in MDD patients relative to HCs. In the MDD group, the MI level in the aMCC positively correlated with the age of onset. LIMITATIONS: The use of the relative concentration of metabolites constitutes a key study limitation. CONCLUSIONS: We observed inconsistent alterations and distribution of neuro-metabolites concentration in the pACC and aMCC, revealing regional metabolic heterogeneity of ACC in first-episode, treatment-naive young individuals with MDD. These results provided new evidence for abnormal neuro-metabolites of ACC in the pathophysiology of MDD and suggested that pACC and aMCC might play different roles in MDD.