Effects of Limited and Extended Pavlovian Training on Devaluation Sensitivity of Sign- and Goal-Tracking Rats

Abstract

Individual differences in Pavlovian approach predict differences in devaluation sensitivity. Recent studies indicate goal-tracking (GT) rats are sensitive to outcome devaluation while sign-tracking (ST) rats are not. With extended training in Pavlovian lever autoshaping (PLA), GT rats display more lever-directed behavior, typical of ST rats, suggesting they may become insensitive to devaluation with more Pavlovian training experience. Here, we use a within-subject satiety-induced outcome devaluation procedure to test devaluation sensitivity after limited and extended PLA training in GT and ST rats. We trained rats in PLA to determine GT and ST groups. Then, we sated rats on either the training pellets (devalued condition) or homecage chow (valued condition) prior to brief non-reinforced test sessions after limited (sessions 5/6) and extended (sessions 17/18) PLA training. GT rats decreased conditioned responding under devalued relative to valued conditions after both limited and extended training, demonstrating they are sensitive to satiety devaluation regardless of the amount of PLA training. While ST rats were insensitive to satiety devaluation after limited training, their lever directed behavior became devaluation sensitive after extended training. To determine whether sign-tracking rats also displayed sensitivity to illness-induced outcome devaluation after extended training, we trained a separate cohort of rats in extended PLA and devalued the outcome with lithium chloride injections after pellet consumption in the homecage. ST rats failed to decrease conditioned responding after illness-induced outcome devaluation, while Non-ST rats (GT and intermediates) were sensitive to illness-induced outcome devaluation after extended training. Together, our results confirm devaluation sensitivity is stable in GT rats across training and devaluation approaches. Extended training unmasks devaluation sensitivity in ST rats after satiety, but not illness-induced devaluation, suggesting ST rats respond appropriately by decreasing responding to cues during state-dependent but not inference-based devaluation. The differences in behavioral flexibility across tracking groups and devaluation paradigms have translational relevance for the understanding state- vs. inference-based reward devaluation as it pertains to drug addiction vulnerability.

Keywords: behavioral flexibility; goal-tracking; outcome devaluation; pavlovian incentive learning; reward; sign-tracking.

Figure 1

Experiment 1: lever- and food cup-directed behaviors during Pavlovian lever autoshaping (PLA). (A) Experimental timeline. We trained rats for five daily reinforced PLA sessions (1–5) to determine their tracking groups. We then tested rats using a within-subject satiety-induced outcome devaluation procedure after limited training. On test days we gave rats 1 h ad libitum access to standard chow (valued) or training pellets (devalued), counterbalanced, prior to 10 min probe tests that consisted of 10 CS presentations under extinction conditions. Between tests, we gave one reinforced PLA session. We gave rats 11 more reinforced PLA (7–17) sessions and repeated identical satiety-induced devaluation testing after extended training. (B–F) Data are mean ± standard error of the mean (SEM) for Pavlovian Conditioned Approach (PCA) scores (B), percentage of time contacting the lever for limited (C) and extended PLA (D), and percentage of time contacting the food cup for limited (E) and extended PLA (F).

Figure 2

Experiment 1: performance during satiety-induced outcome devaluation probe test. Data show mean and individual data points for performance on devaluation probe test by goal-trackers (left column) and sign-trackers (right column), classified based on PCA scores after limited training. (A–C) Goal-trackers’ approach under valued (white bars) and devalued (gray bars) conditions during limited and extended satiety-induced outcome devaluation tests for (A) total behavior (sum of lever and food cup contacts), (B) food cup contacts, and (C) lever contacts. (D–F) Sign-trackers’ approach under valued (white bars) and devalued (gray bars) conditions during limited and extended satiety-induced outcome devaluation tests for (A) total behavior (sum of lever and food cup contacts), (B) food cup contacts, and (C) lever contacts. ^#p = 0.051, *p < 0.05, **p < 0.025, ***p < 0.01.

Figure 3

Experiment 1: performance during extended satiety-induced outcome devaluation probe test after reclassification of tracking groups based on PCA scores after extended training. Data show mean and individual data points. (A) Approach for reclassified GT, INT and ST under valued (white bars) and devalued (gray bars) conditions during extended satiety-induced outcome devaluation tests for (A) total behavior (sum of lever and food cup contacts), (B) food cup contacts, and (C) lever contacts. (D) Preferred responding index during valued relative to devalued conditions for goal-trackers (food cup contact) and sign-trackers (lever contact). Valued preferred responding index = valued preferred responding/(valued + devalued preferred responding). Devalued preferred responding index = devalued preferred responding/(valued + devalued preferred responding). A Preferred responding index value of 0.5 reflects similar responses during valued and devalued conditions. ^#p = 0.056, **p < 0.025, ***p < 0.01.

Figure 4

Experiment 2: performance during illness-induced outcome devaluation probe test after extended PLA. (A) Experimental timeline. We trained rats on 17 sessions of PLA. We split rats into valued (unpaired) and devalued (paired) groups gave 4 days of conditioned taste aversion (CTA) training in the rats’ homecages. After the last day of CTA, we conducted a 10 min probe test that consisted of 10 CS presentations under extinction conditions. Approximately 3 h after the probe test we gave rats 10 min access to 50 training pellets in the magazine of the conditioning chamber. The next day we gave rats 10 min access to 100 training pellets in their homecage to confirm CTA. (B–D) Effect of illness-induced devaluation on (B) total behavior (sum of lever and food cup contacts), (C) food cup contacts, and (D) lever contacts for Non-sign-tracking (Non-ST- made up of GT and INT rats) valued and devalued groups, left; and sign-tracking (ST) valued and devalued groups, right. Data are mean ± SEM and show individual data points. *p < 0.05.