FOS and anxiety disorder: Although immediate early genes (such as c-Fos) are not a ubiquitous marker for studying connectivity, they have been widely used in DBS studies in animal models of mood and anxiety disorders.28, 82 In a recent study, vmPFC HFS induced a profound increase of Zif268 expression, another immediate early gene, in the prelimblic cortical region.82 This is in line with our findings.