ABSTRACT Healthy subjects rapidly shift their attention in response to a dynamic sensory environment and changing cognitive demands. Failure to quickly shift perceptual resources between auditory and other modalities has been hypothesized to be a core deficit in both dyslexia and autism. Precisely how the brain shuttles information between sensory systems is not known, but recent work suggests that the thalamus contains circuits that have the capacity to rapidly transition between different sensory modalities. Specifically, the thalamic reticular nucleus (TRN), a thin shell of GABAergic neurons surrounding the thalamus, may serve as a link to allow communication between different areas of the sensory thalamus, a phenomenon we refer to as thalamic “cross- talk.” Based on recent data and our preliminary findings, we hypothesize that thalamo-TRN- thalamic circuits provide critical connections between thalamic nuclei and therefore permit rapid switching between auditory and other thalamocortical pathways. We propose to test this hypothesis using a novel combination of anatomical, chemogenetic, optical stimulation and optical imaging approaches in the mouse, using both slice and in vivo approaches. Specifically, we will determine which of multiple potential circuit pathways is/are used to permit auditory, visual and auditory thalamic nuclei to communicate with each other. Next, we will determine whether and how such thalamic cross-talk influences synaptic responses at the level of the auditory cortex. Finally, the impact of the TRN on cross-modal processing will be directly examined by optically modulating the TRN while imaging cortical responses to combined sensory stimulation in awake mice. Successful completion of this project will provide the first circuit-level characterization of the role of the TRN in communication between the auditory thalamus and other thalamic regions. In addition, this work will lay the groundwork for a greater understanding of how thalamoreticular systems break down in disorders of communication.