Development of an ethologically relevant task to examine appetitive-aversive trade-offs in rats
Faculty Sponsor(s)
Philip Baker, Ph.D.
Presentation Type
Event
Project Type
Research in progress
Primary Department
Psychology
Description
The lateral habenula (LHb) is involved with multiple neurological pathways implicated in behaviors including working memory, reward motivation, and fear. However, it is unclear if the LHb plays a role in determining when a high value reward option is no longer worth a paired aversive stimulus. In order to address this, we employed a four-armed high/low reward maze (2 45mg pellets vs. 1 45mg pellet) and introduced an air-puff to assess the behavioral threshold in rats choosing the high-reward arm. The reward arms (north and south) and start arms (east and west) remained constant in the task. Training proceeded to an acquisition phase where learned one of the reward arms contained 2 pellets and the other contained a single pellet. Male Long-Evans rats (n = 4) were introduced to this environment and the start/reward arm system before training. On a given pre-air-puff test trial, rats were placed in one of the two start arms and ran to either reward arm to determine their arm preference. Rats were run daily for 30 trials until the rats showed at least 80% preference for the high arm on two consecutive days before the aversive air-puff was introduced. The air-puff was placed in the high-reward arm right at the end and would blow directly over the food well as it approached the reward. Air-puff PSI would rise in increments of 5-10 PSI starting at 5PSI until the rat showed a breaking point in choosing the high reward arm. A breaking point in our study constituted as the rats choosing the high-reward under 50% of trials for 10 consecutive days. The rats had a breaking point of 40PSI±3.49 PSI on average, the average high reward choice for all four subjects following completion of PSI training after the air puff was removed was 90 ±16%. These results suggest that rats are still sensitive to rewards even after extensive training. This preliminary study sets the stage for future LHb inactivation studies of the same design to see how rat behavior could alter in an air-puff situation with an inactivated LHb. Those results would then evaluate whether the inactivation changes the drive of the rat, whether it be a drive to avoid the aversive stimulus, or to continue to consume the high reward.
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Development of an ethologically relevant task to examine appetitive-aversive trade-offs in rats
The lateral habenula (LHb) is involved with multiple neurological pathways implicated in behaviors including working memory, reward motivation, and fear. However, it is unclear if the LHb plays a role in determining when a high value reward option is no longer worth a paired aversive stimulus. In order to address this, we employed a four-armed high/low reward maze (2 45mg pellets vs. 1 45mg pellet) and introduced an air-puff to assess the behavioral threshold in rats choosing the high-reward arm. The reward arms (north and south) and start arms (east and west) remained constant in the task. Training proceeded to an acquisition phase where learned one of the reward arms contained 2 pellets and the other contained a single pellet. Male Long-Evans rats (n = 4) were introduced to this environment and the start/reward arm system before training. On a given pre-air-puff test trial, rats were placed in one of the two start arms and ran to either reward arm to determine their arm preference. Rats were run daily for 30 trials until the rats showed at least 80% preference for the high arm on two consecutive days before the aversive air-puff was introduced. The air-puff was placed in the high-reward arm right at the end and would blow directly over the food well as it approached the reward. Air-puff PSI would rise in increments of 5-10 PSI starting at 5PSI until the rat showed a breaking point in choosing the high reward arm. A breaking point in our study constituted as the rats choosing the high-reward under 50% of trials for 10 consecutive days. The rats had a breaking point of 40PSI±3.49 PSI on average, the average high reward choice for all four subjects following completion of PSI training after the air puff was removed was 90 ±16%. These results suggest that rats are still sensitive to rewards even after extensive training. This preliminary study sets the stage for future LHb inactivation studies of the same design to see how rat behavior could alter in an air-puff situation with an inactivated LHb. Those results would then evaluate whether the inactivation changes the drive of the rat, whether it be a drive to avoid the aversive stimulus, or to continue to consume the high reward.
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