The Associative Mechanism & Neural Correlates of Pavlovian-Instrumental Transfer in Humans

Abstract

The ability to adapt to a changing environment requires the ability to extract predictive information to guide future action. Predictive information regarding the relationship between the performance of an action, or some external stimulus, and the delivery of a rewarding outcome can influence behaviour. Additionally, these processes can interact; reward-predictive stimuli can influence action-selection and guide choice, effects that can be examined in the laboratory using tests of Pavlovian-instrumental transfer (PIT). In these tests, a stimulus associated with a specific outcome biases action-selection towards actions previously been associated with that same outcome (specific transfer – sPIT) whereas a stimulus predicting an outcome not earned by any action can increase the vigour of instrumental responding (general transfer – gPIT). This thesis examines the psychological and neural processes that underlie the expression of PIT in humans. Although extensive research in rodents has attempted to clarify the mechanism through which independently trained Pavlovian stimuli are able to influence action, and the neural circuitry involved in the expression of this effect, to date there has been limited research investigating PIT in humans. To address this, a behavioural task adapted from the rodent literature was used to examine the influence of Pavlovian stimuli on both sPIT and gPIT; i.e., on the effects of predictive stimuli on response bias and response vigour in a comparable manner to the established research in rodents.