Blocking of potentiation of latent inhibition

How common is a common error term? The rules that govern associative learning in sensory preconditioning and second-order conditioning

In standard (first-order) Pavlovian conditioning protocols, pairings of an initially neutral conditioned stimulus (CS) and a biologically significant unconditioned stimulus (US) result in the formation of a CS-US association. The strength of this association is theoretically regulated by prediction error: specifically, the difference between the total level of conditioning supported by the US and the degree to which it is predicted by all stimuli present (i.e., a common error term). In higher-order conditioning protocols (e.g., sensory preconditioning and second-order conditioning), a Pavlovian CS is used to condition responses to other stimuli with which it is paired. At present, it is unknown whether error-correction processes regulate associative learning in higher-order conditioning and, if so, whether these processes are the same as those that regulate formation of a CS-US association in first-order conditioning. Here we review studies that have provided findings relevant to this question: specifically, studies that have examined blocking and/or inhibitory learning in sensory preconditioning and second-order conditioning. These studies show that: (1) animals can form inhibitory associations between relatively neutral sensory stimuli; (2) the learning that occurs in sensory preconditioning and second-order conditioning can be blocked; and, finally, (3) a first-order CS can block conditioning to a second-order CS, and vice versa. The findings are taken to imply that a common error term regulates associative learning in higher-order conditioning, just as it regulates associative learning in first-order conditioning. They are discussed with respect to the nature of the error signal that underlies conditioning and future work that is needed to advance our understanding of the rules that govern different types of learning.

Assessing the inhibitory properties of a latent inhibitor in flavor-aversion learning

In Experiment 1, rats received 16 nonreinforced trials of exposure to a flavor (A) that was subsequently used as the conditioned stimulus in flavor-aversion conditioning. In the critical condition, Flavor A was presented in compound with a different novel flavor on each of the eight daily trials. This treatment produced latent inhibition, in that this preexposure retarded conditioning just as did 16 trials with A alone. Rats in the control conditions, given no preexposure or exposure just to the sequence of novel flavors, learned readily. Experiment 2 examined the effects of these forms of preexposure on performance on a summation test, in which Flavor A was presented in compound with a separately conditioned flavor (X). The preexposure procedure in which A was presented along with novel flavors rendered A effective in inhibiting the response conditioned to X on that test. The conclusion, that this form of training can establish the target stimulus as a conditioned inhibitor, is predicted by the account of latent inhibition put forward by Hall and Rodríguez (2010) which proposes that the latent inhibition effect is a consequence both of a reduction in the associability of the stimulus and of a process of inhibitory associative learning that opposes the initial expectation that a novel event will be followed by some consequence.

Attention as an acquisition and performance variable (AAPV)

This article introduces a new model of Pavlovian conditioning, attention as an acquisition and performance variable (AAPV), which, like several other so-called attentional models, emphasizes the role of variation of cue salience, together with associative strength, in accounting for conditioning phenomena. AAPV is primarily (but not exclusively) a performance-focused model in that it assumes not only that both the saliences and associative strengths of cue representations change during acquisition, but also that they are both influential at the time of test in determining responding. Different weights are given to the representations' associative strengths according to the representations' respective saliences at test. The model also treats the representation of a stimulus that is directly activated by presentation of that stimulus as distinct from the representation of the same stimulus that is activated by presenting a companion of the stimulus. Additionally, extinction is viewed as resulting from a decrease in the salience of the cue's representation, rather than a decrease in associative strength. Simulations of several Pavlovian phenomena are presented in order to illustrate the model and assess its robustness.

Effect of the NMDA antagonist MK-801 on latent inhibition of fear conditioning

N-methyl-D-aspartate (NMDA) receptors seem to play a central role in learning and memory processes involved in Latent Inhibition (LI). In fact, MK-801, a non-competitive NMDA receptor antagonist, has proved its effectiveness as a drug for attenuating LI when administered before or after stimulus preexposure and conditioning stages. This paper presents three experiments designed to analyze the effect of MK-801 on LI when the drug is administered before (Experiment 1A) or after (Experiment 1B) preexposure and conditioning stages with a conditioned emotional response procedure. Additionally, we analyze the effect of the drug when it was administered before preexposure, before conditioning or before both phases (Experiment 2). The results show that the effect of the drug varied as a function of the dose (with only the highest dose being effective), the moment of administration (with only the drug administered before the experimental treatments being effective), and the phase of procedure (reducing LI when the drug was administered only at preexposure, and disrupting fear conditioning when administered at conditioning). These differences may be due to several factors ranging from the role played by NMDA receptors in the processing of stimuli of different sensorial modalities to the molecular processes triggered by drug administration.