Intolerance to delay of gratification
One of the most successful and widely used models of impulsive decision-making which has been adapted for use with rodents is the delay-discounting paradigm. Both humans and animals find delay to reward delivery aversive i.e. the value of a reward can be discounted by the delay to its delivery. Although a large reward is normally valued more highly than a smaller reward, if the delay to the delivery of large reward is relatively long compared to the small reward, the subjective value of the small reward increases relative to the large reward and may surpass it. At this point, the individual may choose impulsively i.e. select a small immediate over a larger but delayed reward. Highly impulsive populations, such as those with ADHD, bipolar disorder, or substance abuse disorder, show steeper discounting curves i.e. shift their preference from large to small rewards even when the delay to the large reward is relatively short.
We use a delay-discounting task adapted for use in rats. We, and others, have shown that this form of impulsive decision-making can be influenced by dopaminergic manipulations, and that this behaviour is controlled by key nodes within the affective cortico-striatal loop. Furthermore, some evidence suggests that there may be competing circuits in the brain, one promoting impulsive choice (including the orbitofrontal cortex and subthalamic nucleus), the other self-control (including the nucleus accumbens and basolateral amygdala). We plan to perform asymmetrical disconnection experiments to determine whether such a hypothesis is true. We are also interested in understanding how using a cue to signal the duration of the delay decreases levels of impulsive decision-making, potentially due to recruitment of dopaminergic signalling in the orbitofrontal cortex.
For more information, email info@winstanleylab.com with “Delay-Discounting” in the subject heading.