In the brain, the lateral habenula is involved in multiple functions such as stress responses and pain processing as neurons in this area have been found be activated when experiencing unpleasant events. More recently, literature suggests that not only does the lateral habenula respond in a reward-negative fashion, it may also play a key role in positive feedback decision making. To investigate the role of the lateral habenula in the decision-making process, we establish a delay discounting task requiring Long Evans rats to make decisions based on wait time and amount of reward received. Given its function in learning and decision making, the lateral habenula is hypothesized to play an indispensable role in positive feedback decision making. Mature Long Evans rats train and run on an elevated T-maze which is set up with two opposing arms and a base arm in between. Rats are trained on which arm provides a greater reward and are then run through a delay discounting task in which the wait time to access the higher reward is incremented from 10 seconds to 20 seconds to 40 seconds between blocks of trails and the wait time for the low reward is maintained at 3 seconds. Their decision is made after reaching the midpoint between the reward arms and once they have decided, they are blocked for the corresponding duration and then allowed to eat the reward. The rats’ recorded brain activity in the lateral habenula while running the delay discounting task will indicate the significance of the lateral habenula’s role in subjective evaluation. These findings will further our understanding of how different regions of the brain work together to make decisions.

Our lives are made up of the choices we make, whether it be choosing to change your posture, choosing an outfit to wear, or choosing a career path. Intertemporal choice is a decision-making process where one needs to change behavioral strategies as the contextual factors in their situation change over time; variables such as working memory, objective and subjective value of the outcome, and motivation influence a subject’s decision in this process. Delayed discounting is an example of an intertemporal choice task, wherein a subject is given a choice of waiting a constant shorter delay to receive a smaller reward (SS, or smaller-sooner), or waiting a longer delay, which increases after a set number of trials, to receive a larger reward (LL, or larger-longer). In the present study, rats are tasked with choosing between waiting 3 seconds for 1 sucrose pellet (SS reward), or waiting 10, 20, or 40 seconds for 4 sucrose pellets (LL reward). Delayed discounting allows investigation into how the Lateral Habenula (LHb) may play a role in integrating signals of objective value and contextual information of the current situation, with internal state information, such as emotion toward and motivation for completing an intertemporal choice, to ultimately allow the subject to behaviorally adapt and make the most beneficial choice. This study predicts that infusion of a combination of baclofen and muscimol via canula into the LHb will inactivate it and subsequently impair delayed discounting in rats, causing them to enter a guessing mode when choosing between SS or LL reward. A dysfunctional LHb could be implicit in clinical disorders such as depression, addiction, or other memory disorder that are characterized by poor control of behaviors; this implication would be able to explain why those with these disorders are unable to switch behavior’s adaptively despite repeated negative consequences.