Inhibition as a "slave" process: Deactivation of conditioned inhibition through extinction of conditioned excitation.

Abstract

Rats were used in a conditioned-suppression paradigm to investigate why a conditioned inhibition (CS-) does not extinguish when presented alone. Experiment 1 assessed the role of blocking by excitatory contextual cues and/or an evoked representation of the conditioned excitor (CS+), which had been nonreinforced in compound with the CS-. When the CS+ and context were extinguished prior to presentations of the CS- alone, the CS- showed a retardation effect, evidently reflecting latent inhibition, because no inhibition was detected in controls for which presentations of the CS- alone had been omitted. Experiment 2 showed that the loss of conditioned inhibition (CI) was due to excitatory extinction and not to time since conditioning. Furthermore, when excitation was reconditioned to the extinguished CS+ (Experiment 1), or to a novel CS in the same context (Experiment 2), CI was restored. Two other experiments evaluated whether the maintenance of CI depended upon excitation that was generic in form or associatively tied to the training context. They showed no loss of CI when groups received CS+ extinction in that context, along with concomitant presentations in a different context of the US by itself, for a novel CS, or correlated either positively or negatively with the original CS+. Collectively, the findings argue that CI is a "slave" to excitation, for when excitation is extinguished, CI is deactivated; and yet when excitation is reconditioned to the original or a new CS+ in the same or a different context, CI is restored.

A comparator view of Pavlovian and differential inhibition.

“…Therefore, at the time of testing the target inhibitor X has a weak (or null) association with the US, but the representation of the US activated indirectly through mediation by A is strong, thereby resulting in behavior indicative of inhibition. Additional support for this view of Pavlovian inhibition has been reported in studies in which, after Pavlovian inhibition training with relatively spaced trials, the training excitor A was extinguished and X lost its control of behavior indicative of inhibition (e.g., Hallam et al, 1990;Lysle & Fowler, 1985). With regard to differential inhibition training, given that the target inhibitor X is never paired with A, the extended comparator hypothesis assumes that the comparator for X is the training context.…”

An Extended Comparator Hypothesis Account of Superconditioning.

“…Moreover, Experiment 2 found that behavior indicative of inhibition was attenuated when the common element shared by the two compounds was presented alone, extinguishing its association to the outcome, after the compound exposures. Several prior studies have found that the extinction of a training excitor used in Pavlovian conditioned inhibition (i.e., Aϩ/ABϪ followed by AϪ) degrades the inhibitory potential of the conditioned inhibitor (e.g., Hallam et al, 1990;Lysle & Fowler, 1985). The consequences of extinguishing A in our Experiment 2 were similar to these previous observations if we regard the unique element, S, that is later paired with the US, as the analog of the US in Pavlovian conditioned inhibition training.…”

“…Several prior studies of first-order conditioned inhibition have revealed that, following Pavlovian conditioned inhibition training (i.e., Aϩ/ABϪ), extinction of the inhibition training excitor (A) can cause a loss of conditioned inhibition (e.g., Hallam, Matzel, Sloat, & Miller, 1990;Lysle & Fowler, 1985). The alternating exposures to two compounds with a common element (e.g., the alternating AB/AS exposures used in Phase 1 of Experiment 1) Figure 3.…”

A response rule for positive and negative stimulus interaction in associative learning and performance

“…Even some effects that, at first sight, could be viewed as belonging to the exclusive domain of the SOCR model, could also be explained if the present response rule employed another learning model. An example is the case of evidence showing that Pavlovian conditioned inhibition (i.e., A US trials interspersed with AX noUS trials, see simulations in Figure 1) wanes following extinction treatment with the excitor (i.e., A noUS trials; e.g., Lysle & Fowler, 1985). This effect can be explained by the SOCR model (again, due to its relying on the extended comparator hypothesis), and could also be explained by our response rule by employing a model that allows learning about absent CSs (e.g., Dickinson & Burke, 1996;Van Hamme & Wasserman, 1994).…”