Aberrant Effective Connectivity Research Articles

The aberrant effective connectivity between the insula and the emotion brain and its relationship with clinical correlation in major depressive disorder

Objective To investigate the functional connectivity of the insula with ventral neural system and the relationship with the clinical feature during emotion processing in major depressive disorder. Methods Twenty-seven patients with major depressive disorder(MDD) and well-matched healthy controls were enrolled in this study. They were asked to recognize the facial emotion during magnetoencephalograph (MEG) scanning. Then the magnetic signals of the sad face was extracted and further processed with the software of SPM8, with the interested regions including the amygdala(AMYG), the insula, the anterior cingulate cortex(ACC), the orbitofrontal cortex(OFC) and the ventromedial prefrontal cortex (VMPFC). The interested time series were selected between 0-600 ms, which was analyzed by the method of principal component analysis (PCA) to reduce the differences. The next step was to compute the effective connectivity of the interested brain areas with the approach of granger causality model(GCM). Results The effective connectivity from the OFC to the ACC was obviously enhanced in MDD(P=0.016), in addition with the connectivity from the insula to the VMPFC(P=0.022) and the ACC(P=0.006) to the insula. Furthermore, the value of the connectivity from the anterior cingulate cortex to the insula was positively correlated with the illness duration(r=0.392, P<0.05). Conclusions The enhanced connectivity of the increased communication between them, indicating the enhancement of the processing of sad stimuli. Our results indicate that the insula plays a pivotal role, not only in the resting-sate, but also in the emotion processing task. Key words: Depressive disorder; Insula; Magnetoencephalogram; Grander causal model

Aberrant Effective Connectivity in Schizophrenia Patients during Appetitive Conditioning

It has recently been suggested that schizophrenia involves dysfunction in brain connectivity at a neural level, and a dysfunction in reward processing at a behavioral level. The purpose of the present study was to link these two levels of analyses by examining effective connectivity patterns between brain regions mediating reward learning in patients with schizophrenia and healthy, age-matched controls. To this aim, we used functional magnetic resonance imaging and galvanic skin recordings (GSR) while patients and controls performed an appetitive conditioning experiment with visual cues as the conditioned (CS) stimuli, and monetary reward as the appetitive unconditioned stimulus (US). Based on explicit stimulus contingency ratings, conditioning occurred in both groups; however, based on implicit, physiological GSR measures, patients failed to show differences between CS+ and CS− conditions. Healthy controls exhibited increased blood-oxygen-level dependent (BOLD) activity across striatal, hippocampal, and prefrontal regions and increased effective connectivity from the ventral striatum to the orbitofrontal cortex (OFC BA 11) in the CS+ compared to the CS− condition. Compared to controls, patients showed increased BOLD activity across a similar network of brain regions, and increased effective connectivity from the striatum to hippocampus and prefrontal regions in the CS− compared to the CS+ condition. The findings of increased BOLD activity and effective connectivity in response to the CS− in patients with schizophrenia offer insight into the aberrant assignment of motivational salience to non-reinforced stimuli during conditioning that is thought to accompany schizophrenia.