PROJECT SUMMARY More than 14 million Americans currently have an alcohol use disorder (AUD) despite decades of research into the effect of alcohol on the brain. One major hurdle to reducing the burden of AUD is understanding how dysfunctions in the nervous system lead to the development and maintenance of alcohol addiction. To expand our understanding of AUD, we must examine novel brain regions and neural circuits and directly probe these targets with alcohol. A brain region of recent interest, the insula (insular cortex), has been heavily implicated in the preoccupation/anticipation stage of the addiction cycle. A prior study in humans indicated that smokers who acquired insula damage show reduced urges to smoke, the initial evidence for the insula’s role in the preoccupation/anticipation stage of the addiction cycle. Yet, there is emerging evidence that the insular has an expanded role in other stages of the addiction cycle. Thus, there is a critical need to investigate insular circuitry to expand our understanding of neuroadaptations associated with AUD. Recently, our laboratory discovered a connection between the anterior insular cortex (AIC) and the dorsolateral striatum (DLS) and established that this circuit is uniquely sensitive to alcohol. While we know AIC-DLS circuit function displays alcohol sensitivity, we do not know how this sensitivity alters alcohol-related behavioral sequences. My preliminary data indicates that when AIC inputs to the DLS (AIC→DLS) are targeted with channelrhodopsin (ChR) and photoactivated during oral alcohol consumption that mice decrease their alcohol intake during DID. I also find that photoactivation does not induce real-time place preference, suggesting this circuitry is not directly modulating valence states, but may be altering encoding and expression of habitual actions, both well-defined striatal-based behaviors known to be altered by alcohol exposure. Together, these data suggest that the AIC plays a more expansive and diverse role in the addiction cycle beyond the preoccupation/anticipation stage than previously thought, but more work must be done to characterize alcohol-mediated AIC-DLS circuit changes. Aim 1 aims to identify how AIC→DLS circuitry is altered by alcohol exposure and how modulating AIC→DLS circuits can alter binge drinking behaviors. Aim 2 focuses on investigating how AIC→DLS circuits effect downstream medium spiny projection neuron activity to modulate striatal-based behaviors such as habitual responding in both alcohol naïve and alcohol exposed animals. Together, these data not only support an expanded role for the AIC as a key mediator of neuroadaptations in AUD beyond the preoccupation/anticipation stage, but also elucidates behavioral sequences governed by novel alcohol sensitive circuitry.