Major depression has previously been associated with abnormalities in REM sleep. Excess REM sleep would diminish noradrenaline, resulting in decreased binding to the ɑ-2 receptor in the medial frontal lobes comprised of the ACC and the medial prefrontal cortex. The absence of REM sleep with TSD may give some participants a break to improve top-down control of the amygdala, resulting in an antidepressant effect.