PROJECT SUMMARY The overall goal of this proposal is to examine the role of emotion regulation (ER) in sleep bruxism (SB). SB is characterized by extreme levels of masticatory muscle activity (MMA) during sleep, expressed as teeth grinding or clenching. SB can lead to clinical consequences, including tooth damage, orofacial pain, and headache. However, there is as yet no curative treatment for SB, and the mechanisms underlying SB are not well understood. To fill this gap, we propose an integrative neurobiological framework that focuses on the involvement of impaired downregulation of wake-time emotion in SB. We will test basic tenets of this framework by addressing four major aims: Aim 1 tests differences in ER processes in individuals with SB (SB+) vs. matched controls (SB?). Aim 2 investigates direct and indirect pathways relating wake-time ER and MMA during sleep among SB+ and SB?. Aim 3 examines whether ER processes can be manipulated in SB+. Aim 4 addresses causal mechanisms by investigating whether more efficient wake-time ER decreases MMA during sleep in SB+ through decreased emotional activation of the amygdala. 100 SB+ and 50 SB? will be defined based on polysomnographic research diagnostic criteria. We will assess functional activations of brain regions of interest during an ER task and conduct ambulatory monitoring of MMA during sleep. In SB+, we will seek to experimentally manipulate ER and assess effects on functional activations of brain regions of interest during the ER task as well as on MMA during sleep. The proposed work is part of a programatic translational research agenda to develop novel effective therapies that target ER processes to alleviate disorders at the intersection of wakefulness and sleep.