| Sarina Iwabuchi, Rajeev Krishnadas, Joaquim Radua, Dorothee Auer & Lena Palaniyappan. Localized connectivity in depression: A meta-analysis of resting state functional imaging studies. Communication among the different subsystems and regional units of the brain becomes perturbed in patients with depressive disorder. Several studies have previously shown that the effective coordination of large-scale networks becomes disrupted in depression. Nevertheless, there is uncertainty over whether this 'large-scale' failure is accompanied by ‘small-scale’ localized breakdown of communication in brain regions. If small sub-systems are failing, where in the brain do we see the maximum 'damage'? We undertook a meta-analysis of resting state studies that measure small-scale voxel to voxel correlation in fMRI signals (a proxy for ‘communication’) and contrast depressed patients with healthy controls. The index that reflects such voxel-to-voxel relationship among a set of neighboring voxels is called ‘regional homogeneity’. A voxel in a MRI scan is similiar to a pixel in a digital photograph. Our meta-analysis revealed that in a depressed patient, most parts of the brain show intact small-scale communication patterns; but some key regions such as the medial prefrontal cortex, which is relevant to our ability to process information about ourselves rather than others (self-processing), show marked disruption in regional homogeneity.
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