Prefrontal cortical functional abnormality in major depressive disorder: A stereotactic meta-analysis
ABSTRACT First, the objective was to test the hypothesis that prefrontal cortical regions most often reported to be maximally abnormal in studies of major depressive disorder, correspond to those regions reported maximally active when healthy subjects engage in diverse emotional tasks. Second, the objective was to determine whether such regions are reported typically to be either over or under-active.
Medline and Embase were used to search for neuroimaging studies of major depressive disorder from 1990 to 2005. Forty-two original studies using voxel based techniques were included, and compared with data from our previous meta-analysis on healthy subjects which included one hundred and eighty-one original studies [Steele, J.D., Lawrie, S.M., 2004b. Segregation of cognitive and emotional function in the prefrontal cortex: a stereotactic meta-analysis. Neuroimage 21, 868-875].
The medial prefrontal cortex is the region reported maximally abnormal most often when healthy subjects experience emotion. The region is centred on Broadmans Area (BA) 32 but extends into BA 25. Two further clusters of reported loci were identified in the lateral prefrontal cortex: one in the lateral orbitofrontal region reported active when healthy subjects experience emotion (BA 47); the other centred on a dorsolateral region (BA 46 and 9) associated with cognitive tasks. No reporting bias for overactivity or underactivity was identified.
This study pooled data from diverse studies deliberately. There were insufficient numbers of original studies to support sub-group analyses.
Despite the variability of reports in the literature, activity reported to be abnormal in depressive disorder is particularly localised to those brain regions that represent the substrate for normal emotional experience in healthy subjects.
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ABSTRACT: It is well established that individuals affected by depression experience difficulty in remembering the past and imagining the future. This impairment is evident in increased rumination on non-specific, generic events and in the generation of fewer specific events during tasks tapping past and future thinking. The present fMRI study investigated whether neural changes during the construction of autobiographical events was evident in depression, even when key aspects of performance (event specificity, vividness) were matched. We employed a multivariate technique (Spatiotemporal Partial Least Squares) to examine whether task-related whole brain patterns of activation and functional connectivity of the hippocampus differed between depressed participants and non-depressed controls. Results indicate that although the depression group retained the ability to recruit the default network during the autobiographical tasks, there was reduced activity in regions associated with episodic richness and imagery (e.g., hippocampus, precuneus, cuneus). Moreover, patterns of hippocampal connectivity in the depression group were comparable to those of the control group, but the strength of this connectivity was reduced in depression. These depression-related reductions were accompanied by increased recruitment of lateral and medial frontal regions in the depression group, as well as distinct patterns of right hippocampal connectivity with regions in the default and dorsal attention networks. The recruitment of these additional neural resources may reflect compensatory increases in post-retrieval processing, greater effort and/or greater self-related referential processing in depression that support the generation of specific autobiographical events.Neuropsychologia 12/2014; 65:41–55. DOI:10.1016/j.neuropsychologia.2014.10.003 · 3.45 Impact Factor
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ABSTRACT: Pediatric bipolar disorder (BD) and unipolar disorder (UD) share common symptomatic and functional impairments. Various brain imaging techniques have been used to investigate the integrity of brain white matter (WM) and gray matter (GM) in these disorders. Despite promising preliminary findings, it is still unclear whether these alterations may be considered as common trait markers or may be used to distinguish BD from UD. A systematic literature search of studies between 1980 and September 2013 which reported WM/GM changes in pediatric and adolescent BD/UD, as detected by diffusion tensor imaging and voxel-based analysis was conducted. Of the 34 articles judged as eligible, 17 fulfilled our inclusion criteria and were finally retained in this review. More abnormalities have been documented in the brains of children and adolescents with BD than UD. Reductions in the volume of basal ganglia and the hippocampus appeared more specific for pediatric UD, whereas reduced corpus callosum volume and increased rates of deep WM hyperintensities were more specific for pediatric BD. Seminal papers failed to address the possibility that the differences between unipolar and bipolar samples might be related to illness severity, medication status, comorbidity or diagnosis. UD and BD present both shared and distinctive impairments in the WM and GM compartments. More WM abnormalities have been reported in children and adolescents with bipolar disease than in those with unipolar disease, maybe as a result of a low number of DTI studies in pediatric UD. Future longitudinal studies should investigate whether neurodevelopmental changes are diagnosis-specific.European Child & Adolescent Psychiatry 09/2014; 23(11). DOI:10.1007/s00787-014-0614-z · 3.55 Impact Factor
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ABSTRACT: Depression is closely linked to the morphology and functional abnormalities of multiple brain regions; however, its topological structure throughout the whole brain remains unclear. We collected resting-state functional MRI data from 36 first-onset unmedicated depression patients and 27 healthy controls. The resting-state functional connectivity was constructed using the Automated Anatomical Labeling template with a partial correlation method. The metrics calculation and statistical analysis were performed using complex network theory. The results showed that both depressive patients and healthy controls presented typical small-world attributes. Compared with healthy controls, characteristic path length was significantly shorter in depressive patients, suggesting development toward randomization. Patients with depression showed apparently abnormal node attributes at key areas in cortical-striatal-pallidal-thalamic circuits. In addition, right hippocampus and right thalamus were closely linked with the severity of depression. We selected 270 local attributes as the classification features and their P values were regarded as criteria for statistically significant differences. An artificial neural network algorithm was applied for classification research. The results showed that brain network metrics could be used as an effective feature in machine learning research, which brings about a reasonable application prospect for brain network metrics. The present study also highlighted a significant positive correlation between the importance of the attributes and the intergroup differences; that is, the more significant the differences in node attributes, the stronger their contribution to the classification. Experimental findings indicate that statistical significance is an effective quantitative indicator of the selection of brain network metrics and can assist the clinical diagnosis of depression.Neural Regeneration Research 01/2014; 9(2):153-63. DOI:10.4103/1673-5374.125344 · 0.23 Impact Factor