[PhD Thesis Presentation] -Hiroaki Hamada- Serotonergic Control of Brain-Wide Dynamic
In this thesis, I performed two experiments in order to understand the serotonergic regulation of brain-wide dynamics. First, I studied short-term and long-term influences of a serotonergic antidepressant on the brain dynamics with functional resonance imaging for rodents. I found that a serotonergic antidepressant, escitalopram, reshapes cortico-limbic functional architecture along time-course of medication. Additionally, long-term serotonergic antidepressant promotes spontaneous behaviors but influence on anxiety-like behaviors showed rather context-dependence and higher individuality. The results imply long-term serotonergic antidepressant enhances intrinsic motivation but not anxiety.
Second, I conducted a pilot experiment to access to serotonergic modulation of brain dynamics by optogenetic stimulation. I found that optogenetic stimulation of serotonin neurons in the dorsal raphe nucleus (DRN) induces brain responses in the frontal cortical regions (the anterior cingulate cortex, the medial prefrontal cortex, and the insular cortex), the striatum, and the ventral tegmental area (VTA). From these experiments, this thesis delineates how serotonin system regulate brain-wide dynamics in short and long time scales.