In a longitudinal study published in Molecular Psychiatry, Runia et al. used an implicit emotional face-viewing functional magnetic resonance imaging (fMRI) task in individuals with TRD before and after vALIC DBS. “Since depression is associated with aberrant amygdala responsivity and functional connectivity, we were interested in studying whether DBS may normalize the amygdala aberrancies,” explains Nora Runia, the first author of the study. Individuals were exposed to different pictures of faces with a given emotional expression, activating the amygdala. In contrast to previous studies, the researchers identified a reduced right amygdala responsivity at baseline in individuals with TRD compared with unaffected controls. “We have previously looked into the TRD neurobiology and it seems it may be a depression subtype with its own neurobiological features. Amygdala responsivity might therefore be variable among individuals with depression and may affect their response to DBS,” Runia adds.
The investigators showed that vALIC DBS, which significantly reduced depression symptoms, normalized amygdala hyporesponsivity. These results were independent of the valence of the emotional faces, which suggests that the DBS effects on amygdala responsivity were not specific to particular emotions. Active vALIC DBS also increased amygdala connectivity with certain cortical areas compared with sham DBS. “As amygdala normalization is probably only one aspect of the neural mechanisms of vALIC DBS, it may be part of a cascade of DBS-induced changes in the brain that are necessary to achieve a response to DBS. We also looked at amygdala functional connectivity with the rest of the brain before and after approximately one year of vALIC DBS and we did not find any differences,” Runia reports.
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