Stimulus-outcome associations are required for the expression of specific Pavlovian-instrumental transfer.

A series of experiments employed a specific Pavlovian-instrumental transfer (PIT) task in rats to determine the capacity of various treatments to undermine two outcome-specific stimulus-outcome (S-O) associations. Experiment 1 tested a random treatment, which involved uncorrelated presentations of the two stimuli and their predicted outcomes. This treatment disrupted the capacity of the outcome-specific S-O associations to drive specific PIT. Experiment 2 used a negative-contingency treatment during which the predicted outcomes were exclusively delivered in the absence of their associated stimulus. This treatment spared specific PIT, suggesting that it left the outcome-specific S-O associations relatively intact. The same outcome was obtained in Experiment 3, which implemented a zero-contingency treatment consisting of delivering the predicted outcomes in the presence and absence of their associated stimulus. Experiment 4 tested a mixed treatment, which distributed the predicted outcomes at an equal rate during each stimulus. This treatment disrupted the capacity of the outcome-specific S-O associations to drive specific PIT. We suggest that the mixed treatment disrupted specific PIT by generating new and competing outcome-specific S-O associations. By contrast, we propose that the random treatment disrupted specific PIT by undermining the original outcome-specific S-O associations, indicating that these associations must be retrieved to express specific PIT. We discuss how these findings inform our theoretical understanding of the mechanisms underlying this phenomenon. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Basal forebrain cholinergic signaling in the basolateral amygdala promotes strength and durability of fear memories.

The basolateral amygdala (BLA) complex receives dense cholinergic projections from the nucleus basalis of Meynert (NBM) and the horizontal limb of the diagonal band of Broca (HDB). The present experiments examined whether these projections regulate the formation, extinction, and renewal of fear memories. This was achieved by employing a Pavlovian fear conditioning protocol and optogenetics in transgenic rats. Silencing NBM projections during fear conditioning weakened the fear memory produced by that conditioning and abolished its renewal after extinction. By contrast, silencing HDB projections during fear conditioning had no effect. Silencing NBM or HDB projections during extinction enhanced the loss of fear produced by extinction, but only HDB silencing prevented renewal. Next, we found that systemic blockade of nicotinic acetylcholine receptors during fear conditioning mimicked the effects produced by silencing NBM projections during fear conditioning. However, this blockade had no effect when given during extinction. These findings indicate that basal forebrain cholinergic signaling in the BLA plays a critical role in fear regulation by promoting strength and durability of fear memories. We concluded that cholinergic compounds may improve treatments for post-traumatic stress disorder by durably stripping fear memories from their fear-eliciting capacity.

General Pavlovian-instrumental transfer tests reveal selective inhibition of the response type - whether Pavlovian or instrumental - performed during extinction.

The present experiments examined whether extinction of a stimulus predicting food affects the ability of that stimulus to energize instrumental performance to obtain food. We first used a general Pavlovian instrumental transfer (PIT) paradigm in which rats were first given Pavlovian conditioning with a stimulus predicting one type of food outcome and were then trained to lever press for a different food outcome. We found that the Pavlovian stimulus enhanced performance of the lever press response and that this enhancement was preserved after extinction of that stimulus (Experiment 1) even when the context was manipulated to favor the expression of extinction (Experiment 2). Next, we assessed whether extinction influenced the excitatory effect of a stimulus when it was trained as a discriminative stimulus. Extinction of this stimulus alone had no effect on its ability to control instrumental performance; however, when extinguished with its associated lever press response, discriminative control was lost (Experiments 3 and 4). Finally, after instrumental and Pavlovian training, we extinguished a Pavlovian stimulus predicting one food outcome with a lever press response that delivered a different outcome. In a general PIT test, we found this extinction abolished the ability of the Pavlovian stimulus to elevate responding on a lever trained with a different outcome, revealing for the first time that extinction can abolish the general PIT effect. We conclude that extinction can produce an inhibitory association between the stimulus and the general response type, whether Pavlovian or instrumental, performed during the extinction training.