Extinction after regular and irregular reward schedules in the infant rat: Influence of age and training duration

Abstract

Greater persistence in extinction is observed following inconsistent reward compared to that observed following consistent reward, an effect termed the partial reinforcement extinction effect (PREE). We report three experiments in which the extinction rates of random partially reinforced (PRF) or continuously reinforced (CRF) infant rat pups were compared to the extinction rate of pups trained with an alternative and regular schedule of partial reinforcement, known as patterned single alternation (PSA). In PSA, subjects learn to alternate speed of responding in anticipation of the regular alternation of reward and nonreward trials in the straight alley runway. In Experiment 1, 17-day-old PSA subjects showed CRF-like extinction rates; whereas in Experiment 2, in which extinction was initiated early in training prior to the onset of the PSA discrimination, PSA subjects showed prolonged, PRF-like extinction curves. In contrast, 12-day-old pups in Experiment 3 showed no reward-schedule-related differences in extinction, despite differences in behavior during acquisition. These results prompt a modification of Amsel's (1962) model of discrimination learning, and suggest the existence of a dissociation between different types of reward-related expectancies in the younger subjects.

The brain metabolic enhancer methylene blue improves discrimination learning in rats

“…The discrimination training consisted of a memorybased daily alternation between rewarded and non-rewarded trials (Lilliquist et al 1999). Beginning on the seventh day, discrimination training sessions began with one non-rewarded/ unbaited trial lasting 5 min or until the fourth hole normally baited was nose-poked.…”

“…The first trial of each day was the non-rewarded trial, thus performance depended on the memory-based discrimination of the daily alternation schedule of reward versus non-reward. Training consisted of more rewarded trials (4) than non-rewarded (1) trials per day to prevent the rapid extinction of reward-seeking performance produced by the presentation of the nonrewarded trials (Lilliquist et al 1999). Discrimination training sessions lasted for 6 days.…”

“…Previous experiments in our laboratory examined the behavior of rats given regular alternation or visual discrimination of rewarded and non-rewarded trials in order to determine reward related expectancies in appetitive memory tasks and associated brain cytochrome oxidase activity, but no prior study has examined the effect of MB on discrimination learning (Hu et al 2005(Hu et al ,2006Lilliquist et al 1999;Nair and Gonzalez-Lima, 1999). We used a more difficult discrimination design than a simple discrimination based on a balanced alternation between reward and non-reward trials because the purpose of this study was to test the efficacy of MB on a more difficult learning task as opposed to a simpler learning task.…”

Development switch in neural circuitry underlying odor-malaise learning

“…For example, prefrontal cortex anatomical maturation occurs between PN8 and PN14, with amygdala connections increasing from PN7 to PN13 and transition to the "adultlike" bilaminar cellular organization by PN13-PN17 (Verwer et al 1996;Bouwmeester et al 2002a,b). At least based on extinction behavior, which involves the prefrontal cortex, this brain area emerges between PN12 and PN17 (Stanton et al 1984;Morgan et al 1993;Lilliquist et al 1999;Nair and Gonzalez-Lima 1999;Nair et al 2001;Milad and Quirk 2002). Hippocampus anatomical development is further delayed, and hippocampaldependent learning emerges near weaning Nadler et al 1974;Baudry et al 1981;Lobaugh et al 1989;Muller et al 1989;Bekenstein and Lothman 1991;Lilliquist et al 1993;DiScenna and Teyler 1994;Rudy 1994;Rudy and Morledge 1994;Nair and Gonzalez-Lima 1999;Kudryashov and Kudryashova 2001;Nair et al 2001).…”

Extinction of Behavior in Infant Rats: Development of Functional Coupling Between Septal, Hippocampal, and Ventral Tegmental Regions

“…Developing rats, for example, show impairments on passive avoidance (Myslivecek and Hassmannova, 1991) and habituation tasks (Bronstein et al, 1971;Feigley et al, 1972) well into the third postnatal week. Likewise, we recently demonstrated that preweanling rat pups trained in a straight alley runway on a schedule of alternating reward and nonreward, known as patterned single alternation (PSA), show different response suppression rates when switched to continuous nonreward (i.e., behavioral extinction): whereas postnatal day 16 (P16)-P17 pups immediately suppress responding during extinction, P11-P12 pups demonstrate significantly slower extinction rates relative to their older counterparts (Lilliquist et al, 1999).…”