Increased Goal Tracking in Adolescent Rats Is Goal-Directed and Not Habit-Like

Abstract

When a cue is paired with reward in a different location, some animals will approach the site of reward during the cue, a behavior called goal tracking, while other animals will approach and interact with the cue itself: a behavior called sign tracking. Sign tracking is thought to reflect a tendency to transfer incentive salience from the reward to the cue. Adolescence is a time of heightened sensitivity to rewards, including environmental cues that have been associated with rewards, which may account for increased impulsivity and vulnerability to drug abuse. Surprisingly, however, studies have shown that adolescents are actually less likely to interact with the cue (i.e., sign track) than adult animals. We reasoned that adolescents might show decreased sign tracking, accompanied by increased apparent goal tracking, because they tend to attribute incentive salience to a more reward-proximal "cue": the food magazine. On the other hand, adolescence is also a time of enhanced exploratory behavior, novelty-seeking, and behavioral flexibility. Therefore, adolescents might truly express more goal-directed reward-seeking and less inflexible habit-like approach to a reward-associated cue. Using a reward devaluation procedure to distinguish between these two hypotheses, we found that adolescents indeed exhibit more goal tracking, and less sign tracking, than a comparable group of adults. Moreover, adolescents' goal tracking behavior is highly sensitive to reward devaluation and therefore goal-directed and not habit-like.

Reward-predictive cues elicit excessive reward seeking in adolescent rats

“…The current findings may also relate to potential differences between adolescent and adult rats in the behavioral systems they relied on to control their reward-seeking behavior. For example, recent devaluation studies suggest that adolescent rats are resistant to developing habits, both in terms of their instrumental lever pressing ( Serlin and Torregrossa, 2015 ; Towner et al, 2020 ) and Pavlovian conditioned approach behavior ( Rode et al, 2020 ). However, this does not readily account for the current findings given that reward-paired cues are more effective in motivating instrumental performance under conditions that promote habitual control ( Holland, 2004 ; Wiltgen et al, 2012 ).…”

Basolateral Amygdala to Nucleus Accumbens Communication Differentially Mediates Devaluation Sensitivity of Sign- and Goal-Tracking Rats

“…Taken together, the BLA and NAc support incentive learning relying on both conditioned stimulus (CS) value and current outcome (US) value. A growing number of studies demonstrate that GT, but not ST, rats flexibly reduce approach after outcome devaluation induced by satiety or illness (Morrison et al, 2015 ; Nasser et al, 2015 ; Patitucci et al, 2016 ; Smedley and Smith, 2018 ; Rode et al, 2020 ; Keefer et al, 2020 ). Both ST and GT rats similarly acquire and express SOC (Nasser et al, 2015 ; Saddoris et al, 2016 ), learning that requires BLA–NAc communication.…”

Optogenetic interrogation of the role of striatal patches in habit formation and inhibition of striatal dopamine

“…This unexpected finding could suggest that patch activation directly drives habitual reward seeking. Previous studies have utilized head entry as a metric for habitual responding and reward devaluation has been shown to reduce head entry in goal-directed animals (DePoy et al, 2016; Morrison et al, 2015; Rode et al, 2020). Discrete head entry and lever pressing events could be ‘chunked’ into larger learned action sequences that are reinforced across habit formation (Dezfouli and Balleine, 2013).…”