Original Article

Neuropsychopharmacology (2011) 36, 913–925; doi:10.1038/npp.2010.230; published online 5 January 2011

Dopamine Modulates Reward Expectancy During Performance of a Slot Machine Task in Rats: Evidence for a ‘Near-miss’ Effect

Catharine A Winstanley1, Paul J Cocker1 and Robert D Rogers2,3

  1. 1Department of Psychology, University of British Columbia, Vancouver, BC, Canada
  2. 2Department of Psychiatry, University of Oxford, Oxford, UK
  3. 3Department of Experimental Psychology, University of Oxford, Oxford, UK

Correspondence: Dr CA Winstanley, Department of Psychology, University of British Columbia, 2136 West Mall, Vancouver, British Columbia, Canada V6T 1Z4, Tel: +1 604 822 3128, Fax: 1 604 822 6923, E-mail: cwinstanley@psych.ubc.ca

Received 7 September 2010; Revised 8 November 2010; Accepted 22 November 2010; Published online 5 January 2011.

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Abstract

Cognitive accounts of gambling suggest that the experience of almost winning—so-called ‘near-misses’—encourage continued play and accelerate the development of pathological gambling (PG) in vulnerable individuals. One explanation for this effect is that near-misses signal imminent winning outcomes and heighten reward expectancy, galvanizing further play. Determining the neurochemical processes underlying the drive to gamble could facilitate the development of more effective treatments for PG. With this aim in mind, we evaluated rats' performance on a novel model of slot machine play, a form of gambling in which near-miss events are particularly salient. Subjects responded to a series of three flashing lights, loosely analogous to the wheels of a slot machine, causing the lights to set to ‘on’ or ‘off’. A winning outcome was signaled if all three lights were illuminated. At the end of each trial, rats chose between responding on the ‘collect’ lever, resulting in reward on win trials, but a time penalty on loss trials, or starting a new trial. Rats showed a marked preference for the collect lever when both two and three lights were illuminated, indicating heightened reward expectancy following near-misses similar to wins. Erroneous collect responses were increased by amphetamine and the D2 receptor agonist quinpirole, but not by the D1 receptor agonist SKF 81297 or receptor subtype selective antagonists. These data suggest that dopamine modulates reward expectancy following the experience of almost winning during slot machine play, via activity at D2 receptors, and this may result in an enhancement of the near-miss effect and facilitate further gambling.

Keywords:

amphetamine; D2 receptor; extinction; gambling; quinpirole; reinstatement

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