Pavlovian Instrumental transfer un modello computazionale bayesiano con cause latenti

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Specific Pavlovian-instrumental transfer: relationship with instrumental reward probabilities

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A Bayesian model for a Pavlovian-instrumental transfer hypothesis

A Pavlovian conditioned stimulus (CS) associated with a reward can enhance an instrumental response directed to the same or other rewards. This effect is called Pavlovian-instrumental transfer (PIT). In recent years, lesion studies using rats have gained insight into its neural substrates dissociating between specific PIT (where CS and instrumental response share the same reward) and general PIT (where they do not) (Corbit and Balleine, 2005, 2011). Despite these advances, the functional differences between specific and general PIT and how Pavlovian cues interact with instrumental response are still not clear. Here we try to explain Pavlovian-instrumental transfer effects by using a latent causes Bayesian model. Previous work in the Pavlovian conditioning literature (Courville et al., 2005) suggests that during Pavlovian conditioning rats do not simply learn associations between two events (CS and reward); instead, they actually try to figure out the real hidden causes behind them by constructing a latent cause model. We expanded that view to include instrumental actions and so explain the interactions between Pavlovian conditioning and instrumental conditioning. Our model correctly reproduces both the presence of specific and general PIT and the absence of general PIT when the CS is associated to the reward of another instrumental action. By framing the PIT effects explanation in Bayesian terms, our model offers a new integrated view on their functional mechanisms and new testable predictions

The relationship between specific Pavlovian instrumental transfer and instrumental reward probability

Goal-directed behavior is influenced by environmental cues: in particular, cues associated with a reward can bias action choice toward actions directed to that same reward. This effect is studied experimentally as specific Pavlovian-instrumental transfer (specific PIT). We have investigated the hypothesis that cues associated to an outcome elicit specific PIT by rising the estimates of reward probability of actions associated to that same outcome. In other words, cues reduce the uncertainty on the efficacy of instrumental actions. We used a human PIT experimental paradigm to test the effects of two different instrumental contingencies: one group of participants had a 33% chance of being rewarded for each button press, while another had a 100% chance. The group trained with 33% reward probability showed a stronger PIT effect than the 100% group, in line with the hypothesis that Pavlovian cues linked to an outcome work by reducing the uncertainty of receiving it. The 100% group also showed a significant specific PIT effect, highlighting additional factors that could contribute to specific PIT beyond the instrumental training contingency. We hypothesize that the uncertainty about reward delivery due to testing in extinction might be one of these factors. These results add knowledge on how goal-directed behavior is influenced by the presence of environmental cues associated with a reward: such influence depends on the probability that we have to reach a reward, namely when there is less chance of getting a reward we are more influenced by cues associated with it, and vice versa

Appetitive pavlovian-instrumental transfer: a review

Reward-related cues are an important part of our daily life as they often influence and guide our actions. This paper reviews one of the experimental paradigms used to study the effects of cues, the Pavlovian to Instrumental Transfer paradigm. In this paradigm, cues associated with rewards through Pavlovian conditioning alter motivation and choice of instrumental actions. The first transfer experiments date back to the 1940s, but only in the last decade has it been fully recognised that there are two types of transfer, specific and general. This paper presents a systematic review of both the neural substrates and the behavioral factors affecting both types of transfer. It also examines the recent application of the paradigm to study the effect of cues on human participants, both in normal and pathological conditions, and the interactions of transfer with drugs of abuse. Finally, the paper analyses the theoretical aspects of transfer to build an overall picture of the phenomenon, from early theories to recent hierarchical accounts