Repeated extinction and reversal learning of an approach response supports an arousal-mediated learning model

Abstract

We assessed the effects of repeated extinction and reversals of two conditional stimuli (CS+/CS−) on an appetitive conditioned approach response in rats. Three results were observed that could not be accounted for by a simple linear operator model such as the one proposed by Rescorla and Wagner (1972): (1) responding to a CS− declined faster when a CS+ was simultaneously extinguished; (2) reacquisition of pre-extinction performance recovered rapidly within one session; and (3) reversal of CS+/CS− contingencies resulted in a more rapid recovery to the current CS− (former CS+) than the current CS+, accompanied by a slower acquisition of performance to the current CS+. An arousal parameter that mediates learning was introduced to a linear operator model to account for these effects. The arousal-mediated learning model adequately fit the data and predicted data from a second experiment with different rats in which only repeated reversals of CS+/CS− were assessed. According to this arousal-mediated learning model, learning is accelerated by US-elicited arousal and it slows down in the absence of US. Because arousal varies faster than conditioning, the model accounts for the decline in responding during extinction mainly through a reduction in arousal, not a change in learning. By preserving learning during extinction, the model is able to account for relapse effects like rapid reacquisition, renewal, and reinstatement.

Chronic stress impairs prefrontal cortex-dependent response inhibition and spatial working memory.

“…Interestingly, when the previous trial was reinforced, control and chronically stressed rats showed similar response latencies. This interaction effect between reinforcement and stress on response latency suggests a ceiling effect of reinforcement on behavioral activation (Salomon & Correa, 2002), and a differential effect of stress on rate of decline in activation in the absence of reinforcement (Killeen, Hanson, & Osborne, 1978; Podlesnik & Sanabria, 2011). That is, chronic stress appeared to speed up the spontaneous decline in behavioral activation.…”

“…That is, chronic stress appeared to speed up the spontaneous decline in behavioral activation. This effect may have important implications for stress-related learning deficits (Podlesnik & Sanabria, 2011; Touyarot, Venero & Sandi, 2004) and tolerance to the reinforcing properties of drugs of abuse (Koob & Le Moal, 2001). This effect is also consistent with the notion that chronic stress reduces incentive motivation, as reported on a progressive ratio schedule (Kleen et al, 2006).…”

Extinction learning deficit in a rodent model of attention-deficit hyperactivity disorder

“…As this study and others [17-19] indicate, free operant responding is composed of multiple underlying components that change over the course of extinction. These changes may reflect the numerous processes implicated in extinction learning, such as reductions in arousal or incentive motivation [28-30], and learning new associations in an unreinforced context [31,32], among many others (see [31,33] for reviews). A precise mapping of these processes to changes in response-bout microstructure during extinction [18] would provide a foundation for inferences about the processes responsible for differences in performance between strains.…”

Extinction under a behavioral microscope: Isolating the sources of decline in operant response rate

“…The absence of the reinforcer has been interpreted to imply the absence of reinforcer-elicited arousal (Killeen et al 1978; Killeen 1998); the absence of the response-outcome contingency has been interpreted to imply the acquisition of a new response-no outcome association (Bouton 2004; Rescorla 2001). How each of these psychological processes, de-motivation and extinction learning, contribute to the decline in response rate is fundamental to the construction of learning models (Podlesnik and Sanabria 2010). …”