Affective Valence Regulates Associative Competition in Pavlovian Conditioning

Abstract

Evidence suggests that, in Pavlovian conditioning, associations form between conditioned stimuli and multiple components of the unconditioned stimulus (US). It is common, for example, to regard USs as composed of sensory and affective components, the latter being either appetitive (e.g., food or water) or aversive (e.g., shock or illness) and, therefore, to suppose different USs of the same affective class activate a common affective system. Furthermore, evidence is growing for the suggestion that, in competitive learning situations, competition between predictive stimuli is primarily for association with the affective system activated by the US. Thus, a conditioned stimulus (CS) previously paired with one US will block conditioning to another CS when both are presented together and paired with a different US of the same affective class, a phenomenon called transreinforcer blocking. Importantly, similar effects have been reported when steps are taken to turn the pretrained CS into a conditioned inhibitor, which activates the opposing affective state to the excitor that it inhibits. Thus, an appetitive inhibitor can block conditioning to a second CS when they are presented together and paired with foot shock. Here we show that the same is true of an aversive inhibitor. In two experiments conducted in rats, we found evidence that an aversive inhibitor blocked conditioning to a second CS when presented in a compound and paired with food. Such findings demonstrate that affective processes and their opponency organize appetitive-aversive interactions and establish the valences on which they are based, consistent with incentive theories of Pavlovian conditioning.

Keywords: Pavlovian conditioning; affect; appetitive-aversive interactions; incentive learning; motivation; prediction error; valence.

Figure 1

A summary of Konorski’s theory of Pavlovian incentive learning. Appetitive (APe) and aversive (AVe) excitors activate sensory specific (S^e) and affectively specific (Ap or Av) components of the US representation to generate consummatory (defensive) or preparatory conditioned responses (CR), respectively. At the heart of this position is an opponency between appetitive and aversive affective systems which are assumed mutually to inhibit one another. One consequence of this view is that it provides a principled account of conditioned inhibition. Thus, appetitive inhibitors (APi) are aversive and so activate the aversive system whereas aversive inhibitors (AVi) are appetitive and activate the appetitive system. As a consequence, inhibitors can influence their concomitant excitors via this mutual inhibitory process (shown in red), reducing preparatory CR’s directly, and consummatory (and defensive) CR’s indirectly by reducing affective activation (dashed arrows).

Figure 2

The opposing effect of an aversive excitor and an aversive inhibitor on appetitive conditioning. (A) Design of Experiment 1; S1/S2/S3/S4: clicker, tone, flashing light or constant light (counterbalanced). (B) Aversive conditioning: S1 became an aversive excitor whereas S2 became into an aversive inhibitor. (C) Appetitive conditioning test: stimulus S3 elicited significantly more appetitive responding than stimulus S4 at test. Error bars denote ± 1 SEM. Asterisks denote significant effect (**p < 0.01).

Figure 3

An aversive excitor enhances, whereas an aversive inhibitor blocks, appetitive conditioning. (A) Design of Experiment 2; S1/S2/S3/S4: clicker, tone, flashing light or constant light (counterbalanced). (B) Aversive conditioning: S1 became an aversive excitor in group Forward and an aversive inhibitor in group Backward whereas S2 was neutral in both groups. (C) In group Forward, stimulus S3 elicited more appetitive responding than stimulus S4. The opposite was found in group Backward. Error bars denote ± 1 SEM. Asterisks denote significant effect (*p < 0.05; **p < 0.01).

Figure 4

Models of appetitive-aversive interaction. (A) An appetitive-aversive continuum account according to which appetitive (λ) and aversive (−λ) events are combined on a substrate to generate the prediction error term for appetitive-aversive interactions. The associative strength of aversive excitors and appetitive inhibitors (AVe+APi) sum (ΣV_av) to drive aversive predictions, aversive prediction errors (−λ+ΣV_av) and inhibition of the appetitive system (ΣVi) whereas the associative strength of appetitive excitors and aversive inhibitors (APe+AVi) sum (ΣV_ap) to drive appetitive predictions, aversive prediction errors (λ−ΣV_ap) and inhibition of the aversive system (−ΣVi). (B) A motivational account on which specific motivational systems combine to emulate appetitive and aversive systems and drive inhibitory connections with systems to which they are not linked. In this example, a hunger (H)—nutrient (Nu) system joins a thirst (T)—fluid (Fl) system to generate appetitive activity and a pain (P)—fear (Fe) system joins an illness (I)—disgust (Di) system to generate aversive activity (blue arrows) and these pairs of systems maintain individual inhibitory links (red arrows) to generate appetitive-aversive interactions.