Effects of the Type of Reinforcer on Renewal of Operant Responding

Some studies have identified that ABA renewal seems to depend on how response-reinforcer contingency is established. Using rats as subjects, the present study assessed ABA and ABB renewal using a two-component multiple schedule (VI30 s - VI30 s) each with a different reinforcer (pellets or sucrose). 16 subjects were trained to lever-press during 20 sessions in Context A; lever-pressing was extinguished during 10 sessions in Context B. And for the renewal test, 8 subjects were tested in Context A (Group ABA); whereas, the rest were tested in Context B (Group ABB). During acquisition, response rates were higher on the pellets component than the sucrose component; during extinction, response rates decreased to near-zero responses. A renewal effect was observed only for Group ABA during test, showing no differences between components. Our results suggest that different type of reinforcers do not seem to affect ABA renewal, using different contexts allows for renewal to be observed regardless of the differences in response rates during acquisition.

Hippocampal Context Processing during Acquisition of a Predictive Learning Task Is Associated with Renewal in Extinction Recall

Renewal is defined as the recovery of an extinguished response if extinction and retrieval contexts differ. The context dependency of extinction, as demonstrated by renewal, has important implications for extinction-based therapies. Persons showing renewal (REN) exhibit higher hippocampal activation during extinction in associative learning than those without renewal (NOREN), demonstrating hippocampal context processing, and recruit ventromedial pFC in retrieval. Apart from these findings, brain processes generating renewal remain largely unknown. Conceivably, processing differences in task-relevant brain regions that ultimately lead to renewal may occur already in initial acquisition of associations. Therefore, in two fMRI studies, we investigated overall brain activation and hippocampal activation in REN and NOREN during acquisition of an associative learning task in response to presentation of a context alone or combined with a cue. Results of two studies demonstrated significant activation differences between the groups: In Study 1, a support vector machine classifier correctly assigned participants' brain activation patterns to REN and NOREN groups, respectively. In Study 2, REN and NOREN showed similar hippocampal involvement during context-only presentation, suggesting processing of novelty, whereas overall hippocampal activation to the context–cue compound, suggesting compound encoding, was higher in REN. Positive correlations between hippocampal activation and renewal level indicated more prominent hippocampal processing in REN. Results suggest that hippocampal processing of the context–cue compound rather than of context only during initial learning is related to a subsequent renewal effect. Presumably, REN participants use distinct encoding strategies during acquisition of context-related tasks, which reflect in their brain activation patterns and contribute to a renewal effect.