Iwabuchi et al., Alterations in effective connectivity anchored on the insula in major depressive disorder
(European Neuropsychopharmacology, in press)
Depression is characterised by two striking difficulties: 1. Loss of the ability to enjoy sensory pleasures such as music, good food or the sight of our loved ones. 2. The inability to shift our focus of thinking from a negative, self-directed mode (ruminations) to the external world. Both of these problems may have a common substrate in a brain region that enables integration of sensory-processing and self-processing. Anterior insula is a strong suspect as it facilitates switching between various brain states.
Using deconvolved Granger Causal Analysis on resting state functional MRI (a technique to study relationship among various brain regions), we have shown that there is a failure of reciprocal influence between insula and higher frontal regions involved in self-processing (dorsomedial prefrontal cortex). This is seen in addition to a weakening of influences from sensory regions (pulvinar and visual cortex) to the insula.
This suggests that there is a dysfunction of both sensory and putative self-processing regulatory loops centered around the insula in depressed individuals. In other words, the hierarchical transmission of information from sensory regions sucha s visual cortex to higher centres such as frontal cortex, may not occur efficiently in depressed individuals.
- First study to demonstrate a network-level processing defect extending from sensory to frontal regions in depression
- First study investigating effective connectivity of the insula in depression
- Published in European Neuropsychopharmacology (IF:5.4)