The Rodent Iowa Gambling Task (rIGT)
One of the most commonly used laboratory-based measurements of gambling-like behaviour in humans is the Iowa Gambling Task (IGT). In this task, subjects choose cards from four decks to accumulate points. The optimal strategy learned by normal volunteers is to choose cards from the two advantageous decks associated with small immediate gains but also low and infrequent losses. Persistent selection from the two disadvantageous decks leads to large immediate gain but heavy losses in the long-term, and reflects a propensity to make risky or impulsive decisions. This pattern of risky decision-making is observed in both pathological gamblers, substance abusers and schizophrenics.
We have recently developed the first model of the IGT for use in rats (rIGT), and it would appear that rats can successfully "play the odds" by choosing between options associated with different amounts of reward but also different amounts and likelihood of punishment/ frustration. Testing takes place in five-hole operant boxes. In the rIGT, rats choose from four illuminated holes, analogous to the four decks of cards in the IGT, in order to earn food reward. Each hole is associated with the delivery of a different number of pellets (1-4). Each option is also associated with a different frequency and duration of "time-out" periods during which animals cannot earn reward. These time-out periods are the equivalent of "losses" in the IGT, and are effectively used as punishments in cognitive behavioural tests. Hence, if the rat chooses an option, it may win the number of pellets linked to that choice or it may instead "lose" and have to endure a time-out during which reward cannot be earned. The reinforcement schedules linked to each reward size are designed so that choosing the options associated with smaller rewards of 1-2 pellets is the safer, more conservative strategy as animals only "lose" on 10-20% of trials, and the length of the frustrating time-outs is relatively short (5-10s). Choosing the larger reward options (3-4 pellets) is more risky as the chance of losing increases to 50-60% and the length of the punishing time out increases to 30-40s. In order to earn the most reward on the task, the rats therefore have to learn to avoid the options associated with the larger rewards analogous to the optimal strategy adopted by people playing the IGT.
Rats' ability to choose the best option can be impaired or enhanced by administration of different drugs. For example, administration of the 5-HT 1A agonist 8-OH-DPAT increases choice of risky options, whereas the dopamine D2 receptor antagonist eticlopride increases choice of the optimal response. We are currently investigating the effects of excitotoxic lesions to different nodes in the affective cortico-striatal loop on rIGT performance.
For more information, email info@winstanleylab.com with "rIGT" in the subject heading.
If you would like a copy of our rIGT Med PC program code, please email info@winstanleylab.com with [Code Request] in the subject heading.