Project Summary The human brain is active all the time. Spontaneous brain activity is richly structured across space and time, and disruption of its organization carries serious clinical consequences. Yet, how spontaneous brain activity participates in online brain functioning remains an open question. In the perceptual domain, it is well established that prestimulus spontaneous activity can influence perceptual outcome, but exactly how it participates in stimulus and perceptual processing remains poorly understood. This gap in knowledge hinders our ability to explain and treat perceptual disturbances in a wide range of clinical disorders. The proposed project aims to close this gap. Two competing hypotheses about the functional mechanisms of spontaneous brain activity have been proposed: one proposes that it carries specific functional information shaped by previous sensory experiences; the other suggests that it largely reflects nonspecific changes in arousal or behavioral states. Recent work from our laboratory provided evidence that both hypotheses are correct and, in fact, two separate spontaneous processes coexist in the human brain that influence perception in a content-specific and a non-content-specific manner. In addition, these two spontaneous processes appear to have doubly dissociable influences on perceptual outcome, impacting sensitivity and criterion, respectively. These preliminary findings point to a novel, unifying framework for conceptualizing the functional (dual) role of spontaneous brain activity in perception. Here, we combine two advanced human brain imaging technologies with complementary spatial and temporal resolution—7-Tesla functional magnetic resonance imaging and magnetoencephalography—to test this new framework and address several urgent questions. Aim 1 (Anatomy): Which brain structures generate perceptually relevant content-specific and non-content-specific spontaneous brain activity? Aim 2 (Modality specificity): Which components of perceptually relevant spontaneous activity are constrained within a sensory modality and which components are shared across sensory modalities? Aim 3 (Cognition): Does perceptually relevant spontaneous activity have shared neural substrate with task-specific anticipatory brain activity? Answering these questions will reveal the neural underpinnings and functional mechanisms of perceptually relevant spontaneous brain activity. The proposed research will shed light on how spontaneous brain activity shapes perceptual processing and lay the foundation for a more mechanistic understanding of perceptual disturbances in a variety of neuropsychiatric illnesses. Our innovative approach will test a novel framework that has the potential to unify current competing theories and combine two complementary, cutting-edge technologies to monitor human brain activity. This work will advance knowledge of how spontaneous activity is involved in brain functions and produce insights that help to refine t...