Adolescent and Young Adult Perceptions of Online Versus In-Person Cognitive-Behavioral Therapy for Eating Disorders.

Microglia are the resident immune cells of the central nervous system [–]. Two hematopoietic progenitor sources give rise to mouse microglia each with distinct ontogenies and functions []. The first during development are canonical non- microglia progenitors, born in the yolk sac at gestation day 7.5 (E7.5) and then migrating directly into the developing brain starting at E9.5, once the vasculature is formed []. The second population of progenitors, microglia, are also born in the yolk sac but a day later (E8.5) and then migrate to the AGM (Aorta-Gonad-Mesonephros) and fetal liver, where they are amplified 16 and 280-fold respectively, before their migration into the developing brain starting at E12.5 [, ]. is a transcription factor belonging to a family of genes that specify body plans during development. The etiology of these two populations of microglia show similarity but also significant differences during mouse development and in adults. Both microglial populations are capable of self-renewal. Once the blood-brain barrier is formed there is minimal microglial exchange with the periphery. Steady-state levels of both microglial populations are maintained through a combination of proliferation and apoptosis [–]. Approximately 75% and 25% of total microglia in the adult brain, are composed of canonical non- microglia and microglia, respectively []. Molecularly, the two populations of microglia are very similar with only ~20 genes exhibiting two-fold or more differential expression (6, and unpublished results). Both populations of parenchymal microglia express similar high levels of (a transcription factor) (a membrane protein) and (a G-protein coupled receptor) that distinguish them from other brain macrophages and thereby establishing that microglia as well as non- microglia are bona fide parenchymal microglia [, ]. Disruption of the gene in mice gives rise to both chronic anxiety and pathological overgrooming resembling trichotillomania, a type of Obsessive-Compulsive Spectrum Disorder (OCSD) [, –]. We have reported that optogenetic activation of microglia in specific regions of the brain induces higher levels of anxiety, grooming or both []. Optogenetic stimulation of microglia within the dorsomedial striatum (DMS) or the medial prefrontal cortex (mPFC) induces grooming. In contrast, stimulation of microglia in the basolateral amygdala (BLA) or central amygdala (CeA) does not induce grooming but instead elevated levels of anxiety. Optogenetic stimulation of microglia in the ventral CA1 region of the hippocampus (vCA1) induces both behaviors, as well as freezing [], a reflection of mouse anxiety.