Decision-making is critical for survival but is a complex process to understand at the level of brain function. Animals and humans alike can use two strategies to solve problems of decision-making: goal-directed or habitual behavior. Habits emerge late in training as animals transition from reliance on a goal-directed strategy to a habit with experience. Biologically, habits are known to develop via communication between a network of areas that span across the brain. Of particular interest for habit formation are the prefrontal cortex (IL), the sensorimotor striatum (DLS), dopaminergic projections to the striatum (SNc), and the central nucleus of the amygdala (CeA). Previous work has shown that a characteristic neuronal signature develops in IL and DLS, where as a habit develops, single-unit neuronal activity accentuates the beginning and end of actions of the behavior as it becomes well-learned. Importantly, as habits are comprised of multiple components (e.g. efficiency of action sequences and insensitivity to goal value), these individual features correlate with neural activity in distinct brain areas across the habit network (IL: outcome devaluation insensitivity, DLS: action vigor). However, there is a gap in knowledge in how activity in the central nucleus of the amygdala (CeA) codes habits or how that activity relates to the function of these other interconnected areas The objective of this project is to define how neural activity in CeA contributes to habit formation and whether a distinct component of behavior correlates with neural activity. The rationale is that the habit network is conserved across mammals as habits are ubiquitous and the potential for basic research to translate into bettering the human condition is high. The central hypothesis is that CeA neurons will develop a ?chunking? pattern of activity that is necessary for a habit to develop, with behavioral correlates of this neural activity similar to those that correlate with IL. Guided by methods and data from Specific Aim 1, where behavioral phenotypes of habit and methodology to test habit formation are addressed, Specific Aim 2 will, through in-vivo electrophysiology, determine if CeA activity brackets in a manner similar to IL, DLS, and SNc as a habit forms on an elevated plus-maze task.
Specific Aim 3 details a plan to identify and pursue a postdoctoral research fellowship upon completion of the dissertation work described in Specific Aim 2. Overall, the proposed experiment has the potential to provide mental health clinicians and researchers significant insight into how compulsive actions may arise from improperly timed amygdalar activity and will further define how neural activity can contribute to psychological phenomena such as habit formation.
Habits have a remarkable level of control over our everyday behavior, and they can be helpful (e.g., routine exercise) or detrimental (e.g., compulsive eating) to one?s well-being. Animal research has revealed specific brain areas that govern habit formation, allowing for further investigation to resolve finely timed neural mechanisms related to the acquisition and expression of habits. The project proposed here is pertinent to NIH?s mission that relates to developing necessary knowledge and insight about the precise neural mechanisms underlying how habits are controlled, how habits can be contextualized as arising from a network of brain areas, and how adulterations of normal habit signaling might contribute to obsessive-compulsive disorder, Tourette syndrome, and compulsive eating.
