Conditioned Inhibition Training Research Articles

Comparator mechanisms and conditioned inhibition: Conditioned stimulus preexposure disrupts Pavlovian conditioned inhibition but not explicitly unpaired inhibition.

Three conditioned lick-suppression experiments with rats examined the effects of pretraining exposure to the conditioned stimulus (CS) on behavior indicative of conditioned inhibition. After CS-preexposure treatment, subjects received either Pavlovian conditioned inhibition training or explicitly unpaired inhibition training with the preexposed CS. The inhibitory status of the CS was then assessed with a retardation (Experiment 1) or a summation (Experiment 2) test. Experiment 3 controlled for the unconditioned stimulus-preexposure effect being a potential confound in Experiments 1 and 2. As predicted by the comparator hypothesis (R. R. Miller & L. D. Matzel, 1988), the CS-context association that developed during the CS-preexposure phase disrupted the expression of Pavlovian conditioned inhibition but not the expression of explicitly unpaired inhibition.

Lesions of the perirhinal cortex interfere with conditioned excitation but not with conditioned inhibition of fear.

Posttraining lesions of the perirhinal cortex (Prh) have been shown to interfere with the expression of fear. This study assessed whether Prh lesions would also disrupt the inhibition of fear as measured with conditioned inhibition of fear-potentiated startle. Following light + shock, noise-->light-no shock conditioned-inhibition training, rats were given Prh lesions. The lesions interfered with the expression of fear-potentiated startle to the light. To assess whether conditioned inhibition was affected, the rats were given light + retraining without additional noise-->light-training. The noise-conditioned inhibitor retained its ability to inhibit fear-potentiated startle to the retrained light. These results suggest that the areas of the Prh that are essential for the initial expression of conditioned fear are not important for the expression of conditioned inhibition of fear.

Lesions of the central nucleus of the amygdala block conditioned excitation, but not conditioned inhibition of fear as measured with the fear-potentiated startle effect.

Lesions of the amygdala block the expression of fear-potentiated startle following either moderate or extensive light + shock training. The present experiment assessed whether lesions of the amygdala would also block the expression of conditioned inhibition of fear. Rats were given conditioned inhibition training in which a light was paired with shock and a noise and light compound was presented in the absence of shock. Then half of the rats were given bilateral electrolytic lesions of the amygdala and the remaining rats were sham operated. Lesions of the amygdala blocked the expression of fear-potentiated startle to the light. To assess whether conditioned inhibition was disrupted, rats were retrained with light + shock pairings with no further conditioned inhibition training. Amygdala lesioned rats reacquired fear-potentiated startle to the light (Kim & Davis, 1993). Importantly, the noise conditioned inhibitor retained its ability to inhibit fear-potentiated startle to the retrained light. These results indicate that areas of the amygdala critical for initial performance of fear-potentiated startle are not critical for the expression of conditioned inhibition.

Renewal of Pavlovian conditioned inhibition

Prior research has demonstrated renewal, which is the ability of contextual cues to modulate excitatory responding to a Pavlovian conditioned stimulus (CS). In the present research, conditioned lick suppression in rats was used to examine similar contextual modulation of Pavlovian conditioned inhibition. After Pavlovian conditioned inhibition training with a CS in one context, subjects were exposed to pairings of the CS with an unconditioned stimulus (US) either in the same or in a second context. Results indicated that, when the CS was paired with the US in the second context, the CS retained its inhibitory control over behavior, provided that testing occurred in the context used for inhibition training. However, when the CS-US pairings occurred in the inhibition training context, the CS subsequently proved to be excitatory regardless of where testing occurred. These observations indicate that conditioned inhibition is subject to renewal.

Conditioned inhibition of rotation-induced taste aversion

In three experiments, we investigated the existence of conditioned inhibition of body rotation-induced taste aversion. Rats were given conditioned inhibition training in which the taste of saccharin was always followed by rotations, but the taste of vanilla was not. Flavor-preference tests, retardation-of-acquisition tests, and summation tests of inhibition indicated that the vanilla stimulus had acquired conditioned inhibitory properties. These findings could not be interpreted as functions of either initial solution preferences or simple nonassociative effects of flavor preexposure. They lend support to a theory that views learning mechanisms as being central to the phenomenon of motion sickness, and suggest that inhibitors might be effectively employed to ameliorate its symptoms.

Superconditioning and overshadowing

Conditioned lick suppression by water-deprived rats was used to investigate the phenomenon of superconditioning. In Experiment 1, animals received explicitly unpaired conditioned inhibition training with CS A or CS B and a footshock US. Both groups then received pairings of a CS A-light compound with shock. In testing, animals for which CS A was inhibitory displayed enhanced responding to the light, relative to animals for which CS A was associatively neutral. Thus, superconditioning relative to the conventional control group was demonstrated. However, an additional control group that first received inhibitory training with CS A and then the light alone paired with shock exhibited as much suppression to the light as the superconditioning group. This control, which was omitted from previous demonstrations of superconditioning, suggests that superconditioning is merely attenuated overshadowing of the added element by CS A as a result of prior inhibitory training with CS A. In Experiment 2, superconditioning was not obtained when partial reinforcement of CS A occurred during negative contingency training, despite the fact that in prior research the identically trained CS A had passed both summation and retardation tests for inhibition. In Experiment 3, exposure to CS A alone (i.e., latent inhibition treatment) sufficed to produce a superconditioning-like effect with respect to the light when the CS A-light compound was later paired with shock. In Experiment 4, conditioned inhibition and latent inhibition treatments of CS A were found to yield equivalent superconditioning-like effects with respect to the added element. Collectively, these studies suggest that superconditioning arises from a reduction in overshadowing and a comparable effect can be obtained through any initial treatment that diminishes the associability of the overshadowing CS.

The effects of post-stress exposure to alcohol upon the development of alcohol consumption in rats

A preference-drinking situation was used to test the effects of conditioned inhibition training upon relative alcohol preference. Using a backward, conditioned inhibition paradigm, water-deprived rats received daily shock presentations, followed immediately by alcohol exposure in a different neutral chamber. This post-shock exposure to alcohol drinking cues increased daily alcohol intake in the home cage, as tested 5 h later, relative to a no-shock control group. Results were interpreted in terms of a conditioned antagonistic-response interpretation of conditioned inhibition—increased relative preference for alcohol cues developed as a result of the association of alcohol cues with a post-shock, relief/relaxation response. These results have implications for the role of conditioned inhibitory processes in the initial development of alcoholism.

Conditioned inhibition in taste aversion learning: Testing methodology and empirical status

Several assays were used in assessing conditioned inhibition within a taste aversion procedure. Following Pavlovian conditioned inhibition training, in which one taste was followed by an injection of LiCl on A+ trials, but was followed by access to a second flavored solution on AX− trials, retardation-of-acquisition and summation tests failed to indicate that the X stimulus (NaCl) had become inhibitory. Nor was the X stimulus consistently preferred to water or dilute quinine in two-bottle tests, contrary to an earlier report (Best, 1975).

Latent inhibition experiments with goldfish (Carassius auratus).

Evidence of latent inhibition was sought in a series of experiments with goldfish. In Experiment 1, goldfish were given nonreinforced preexposure to a color that subsequently predicted shock in an activity conditioning situation; their performance did not differ from that of control animals preexposed to a markedly different color. In Experiment 2, a group of goldfish given nonreinforced preexposure to a tone and an unstimulated control group were trained in an appetitive situation, with the tone serving either as a conditioned excitor or as a conditioned inhibitor. Preexposure had no significant effect in the conditioned excitation training, but it reduced the level of responding both to the positive stimulus and to the negative compound in the conditioned inhibition training. In Experiments 3 and 4, classical aversive conditioning was studied in the shuttle box. In Experiment 3, excitatory conditioning to a color was found to be impaired (relative to the performance of nonpreexposed control animals) as much by nonreinforced preexposure to the training color as by nonreinforced preexposure to a markedly different color; substantial variation in amount of preexposure was without significant effect. In the conditioned inhibition training of Experiment 4, animals with nonreinforced preexposure responded less than did unstimulated control animals both to the positive stimulus and to the negative compound. The results for goldfish can be understood on the assumption that the effect of preexposure in these animals is simply to reduce general responsiveness or level of arousal.

Efficient conditioned inhibition of the rabbit’s nictitating membrane response with massed training

Using a light (L) as the reinforced CS and a tone (T) as the conditioned inhibitor, rabbits received conditioned inhibition (CI) training of the nictitating membrane response. In Experiment 1, animals were matched in terms of initial acquisition to L and T, using electric shock to the eye as the UCS to form three groups. Group 100 received 100 CI trials per single daily session, Group 200 received 200 CI trials per single daily session, and Group 100/100 received 200 daily trials in two sessions separated by an interval of approximately 3 h. Each unit of 100 trials consisted of 50 reinforced L trials (L+) and 50 nonreinforced L-T compound trials (LT-). The development of suppressed conditioned responding over the course of 1,300 CI trials and the results of a retardation test (T+) failed to detect differences among these three trials-distribution procedures. Experiment 2 examined the development of CI using the two-session/day procedure with intersession intervals of 3 and 6 h. No differences in CI were apparent over the course of 2,000 trials or in the retardation test. These findings suggest robust CI can be obtained with relatively massed training and that theories of CI might minimize the role of distribution of training in their formulations.

Amplitude of the rabbit’s unconditioned nictitating membrane response in the presence of a conditioned inhibitor

Using a light or backshock as the reinforced CS (A) and a tone or backshock as the conditioned inhibitor (X), rabbits experienced conditioned inhibition training in an A+/AX− paradigm. Following training, the amplitude of the unconditioned nictitating membrane response elicited by a mild (.5-mA) paraorbital shock was measured in the presence of X and AX and expressed as a percentage of the amplitude of the UR to the shock presented alone. In Experiment 1, the effect of X and AX on UR amplitude for conditioned inhibition animals was compared with that of control animals treated to a variety of pretest procedures. In general, UR amplitude in the presence of X exceeded that observed to the US presented alone. There was no consistent difference between the experimental and control groups. In Experiments 2–5, A test trials were added as an alternative reference point. Again, UR amplitude increased rather than decreased UR amplitude. In addition, X as a conditioned inhibitor enhanced the facilitating effect of A on UR amplitude in four out of five experiments. These findings have implications for theories of the “locus of action” of conditioned inhibitors.

Stimulus-reinforcer and response-reinforcer relations in the control of conditioned appetitive headpoking (“goal tracking”) in rats

Experiment 1 studied the effect of several Pavlovian appetitive conditioning procedures on rats' headpoking into a food tray (goal tracking). The procedures included forward delay conditioning, CS-alone extinction, differential conditioning, and simultaneous compound conditioned inhibition training. In general, the headpoke behaved in all of these treatments much like a Pavlovian CR; however, one could also say that the headpoke behaved like an adventitiously reinforced operant for which the CS was an S D. Experiment 2, therefore, used the differential-nondifferential technique ( E. Gamzu & D. R. Williams, Science, 1971 , 171, 923–925), and Experiment 3 used an omission technique ( F. D. Sheffield, in W. F. Prokasy, Ed., Classical conditioning, New York: Appleton-Century-Crofts, 1965 ; D. R. Williams & H. Williams, Journal of the Experimental Analysis of Behavior, 1969 , 12, 511–520), to try to separate the role of stimulus-reinforcer and response-reinforcer relations in controlling the headpoke. These techniques proved inadequate. The results of Experiment 2 could be given either operant or Pavlovian interpretations. Those of Experiment 3 showed that headpoking is dominated by response-reinforcer, rather than by stimulus-reinforcer, relations when the two compete but forced no conclusion about which dominates when the two act together as in acquisition. Implications for pigeon autoshaping are discussed.

Odor as a conditioned inhibitor: Applicability of the Rescorla-Wagner model to feeding behavior

Hooded rats were given conditioned inhibition training in which the taste of saccharin alone was always followed by induced illness, but the taste of saccharin plus the odor of amyl acetate was not. In a series of three subsequent tests—summation, enhancement of conditioning, and retardation—it was demonstrated that the odor had acquired active inhibitory properties. The results paralleled those obtained with more traditionally studied stimuli and techniques and hence were found to be readily predictable from a recent model of conditioning set forth by Rescorla and Wagner (1972).

Electrical brain stimulation as the reinforced CS in Pavlov's conditioned inhibition paradigm

Rabbits received Pavlovian conditioned inhibition training (nictitating membrane response) using ESB as the reinforced CS and a tone as the conditioned inhibitor. Summation, retardation, and generalization tests indicated that the use of ESB in the paradigm did not interfere with the development of inhibitory control by the tone.

Electrical brain stimulation as a Pavlovian conditioned inhibitor

Rabbits received differential conditioning in a Pavlovian conditioned inhibition pardigm utilizing electrical brain stimulation (ESB) as CS-. The reference response was the nictitating membrane reflex elicited by electric shock to the infraorbital region of the eye. A 1200 Hz tone served as the reinforced CS, and a compound consisting of the same tone plus ESB was the nonreinforced CS. The major findings from a series of three experiments were as follows: (a) ESB served as a true conditioned inhibitor when inhibitory potential was assessed in summation and retardation tests and contrasted with pseudoconditioned inhibition controls; (b) the effectiveness of ESB as a conditioned inhibitor was not related to locus (hypothalamus, lateral geniculate, medial geniculate nucleus) of stimulation; and (c) tests of stimulus generalization following conditioned inhibition training indicated that concurrent ESB lowered the (concave downward) generalization gradient along the audiofrequency dimension. The fact that concurrent ESB did not eliminate or invert the gradient suggests that the 1200 Hz tone retained its excitatory potential in the presence of the inhibitory CS. These findings were related to a hierarchial neuronal model of inhibitory stimulus control.

Inhibitory stimulus control of the classically conditioned nictitating membrane response of the rabbit

Pavlovian conditioned inhibition training provides a method for investigating inhibitory dimensional stimulus control of the rabbit’s conditioned nictitating membrane response. The basic technique consists of reinforcing a burst of white noise while a compound made up of white noise and a tone is systematically not reinforced. Generalization tests to the white noise and a series of test tones result in a U-shaped gradient which remains relatively stable over a series of training-test phases.