Reward comparison: the Achilles’ heel and hope for addiction

Abstract

In the words of the late Charles Flaherty, reward comparison is commonplace. Rats and man, it appears, compare all rewards and this capacity likely contributes to our ability to select the most appropriate reward/behavior (food, water, salt, sex), at the most ideal level (e.g., a certain sweetness), at any given time. A second advantage of our predisposition for reward comparison is that the availability of rich alternative rewards can protect against our becoming addicted to any single reward/behavior. Thus, the potential protective effects of natural rewards/enrichment are addressed. Despite this, behavior can become inflexible when, through the development of addiction, stress, drug, or cues elicit craving, withdrawal, and ultimately, drug-seeking. Drug-seeking corresponds with a 'window of inopportunity', when even potent natural rewards have little or no impact on behavior. During this time, there is a unitary solution to the need state, and that solution is drug. The present animal model explores this 'window of inopportunity' when natural rewards are devalued and drug-seeking is engaged and considers a mode of possible intervention.

Anti-anxiety self-medication induced by incentive loss in rats

“…The reasons for these discrepancies across experiments are unclear. The between-experiment difference in ethanol consumption may reflect the protective effect of sucrose consumed during the training session on subsequent intake of ethanol [36]. Whatever the reason for these differences, the present results add to a growing body of evidence suggesting that otherwise analogous consummatory and instrumental tasks may, in fact, activate different brain mechanisms, as shown by lesion and pharmacological manipulations [11,37].…”

When a good taste turns bad: Neural mechanisms underlying the emergence of negative affect and associated natural reward devaluation by cocaine

“…For example, we reported that interruption of cocaine access following self-administration caused a dramatic increase in the number and strength of NAc neurons that encode cocaine-related information (Hollander and Carelli, 2005), a heightened activation of NAc neurons by cocaine-associated stimuli (Hollander and Carelli, 2007), and enhanced drug seeking during extinction that was encoded by distinct populations of NAc neurons (Cameron and Carelli, 2012; Hollander and Carelli, 2007). We also reported a shift in neural signaling toward more cocaine-related processing (as opposed to food) following abstinence that may be relevant to the decrease in reinforcing properties of natural rewards reported by human drug addicts (Gawin, 1991; Grigson, 2008). Critically, Grigson and Twining (2002) showed that following 1-month cocaine abstinence the devaluation of a natural reward by cocaine was maintained, and that abstinence exacerbated drug seeking during extinction (i.e., incubation of craving).…”

“…Further, this aversive state is exacerbated following prolonged cocaine abstinence [(Grigson and Twining, 2002) and Fig. 7], and is observed with other abused substances (Parker, 1995; Gomez et at al., 2000; Grigson, 2008; Nyland and Grigson, 2013). Thus, understanding the neurobiological mechanisms mediating the emergence of negative affective states and associated devaluation of natural rewards by cocaine could led to novel pharmacological treatments that ameliorate this detrimental consequence of repeated drug use, help refocus the addicts interest toward natural reward procurement, and attenuate the continued drive (craving) for the drug.…”

“…We noted that rats would stop lever pressing for the natural reward when that lever consistently preceded the drug lever (unpublished finding). This was a fascinating observation given the work by Grigson and others that showed that animals will respond less for a previously palatable natural reward when it comes to predict an abused drug (Grigson, 1997, 2000, 2008; Grigson and Twining, 2002; Wise et al, 1976). Here, we review our work that examined a role of the NAc in natural reward devaluation by cocaine using a novel behavioral model in combination with electrophysiological and electrochemical approaches.…”

Relative reward effects on operant behavior: Incentive contrast, induction and variety effects

“…Exploring reward comparison is a vital area of research in experimental psychology and behavioral neuroscience and animal models of behavioral pathology (Grigson, 2008). The modified approach of the present study using a chain of operant responses could enable investigation on interaction between external factors including conditioning and learning that play a role in contrast and other forms of reward comparison.…”