Single Conditioning Trial Research Articles

An investigation of the role of dopamine in the antennal lobes of the honeybee,Apis mellifera

The effects of dopamine applied to the antennal lobes of the honeybee are investigated using the proboscis conditioning paradigm (Kuwabara 1957). The percentage of bees responding to a conditioned olfactory stimulus after a single conditioning trial is reduced significantly by the application of dopamine (10−6M) to the antennal lobes of the bee brain. Reduction in response levels is significantly smaller in bees conditioned to the olfactory stimulus in multiple conditioning trials prior to treatment with dopamine. The effects of dopamine on the percentage of bees responding to a conditioned olfactory stimulus are blocked by the butyrophenone, haloperidol (10−5M). The possible role of dopaminergic interneurones in the antennal lobes of the bee brain is discussed.

The effects of extensive taste preexposure on the acquisition of conditioned taste aversions

Animals extensively exposed to water during rearing showed no evidence of a conditioned taste aversion to water following a single pairing of water and lithium chloride (LiCl), indicating that, with sufficient preexposure, conditioned taste aversions can be completely attenuated. Although showing no aversion following a single conditioning trial, the preexposed subjects completely avoided water when repeated water-LiCl pairings were given, indicating further that, on the initial conditioning trials, some association had been established between the taste and toxicosis but that it was too weak to affect behavior, in other words, was a silent association. With repeated conditioning trials, this weak association became sufficiently strong to suppress consumption. The data were discussed in terms of the effects of taste preexposure on the acquisition of conditioned taste aversions.

A Re-Examination of One-Trial Blocking in Conditioned Suppression

Three experiments on the conditioned suppression of licking in rats examined the amount of conditioning produced by a single conditioning trial to a clicker-light compound and the effect of prior conditioning to the light on the level of conditioning to the clicker. In Experiment I, prior conditioning to the light, far from blocking conditioning to the clicker, actually enhanced it, whether the clicker was presented in a simultaneous compound with the light or in a serial compound preceding the light. Experiment II, however, showed that this potentiation effect could be abolished if a trace interval was inserted between the clicker and light in the serial compound arrangement. Moreover, Experiment III demonstrated a significant blocking effect when a trace interval separated the clicker and light on the single compound trial. These results establish that one-trial blocking of conditioned suppression is possible, and suggest that in some earlier studies blocking may have been masked by higher-order conditioning to the target stimulus.

Specificity of cue to consequence in aversion learning in the rat: Control for US-induced differential orientations

In four experiments, each using a single conditioning trial, rats avoided a light more than a saccharin solution after these stimuli had been paired with footshock, whereas saccharin was avoided more than the light after these stimuli had been paired with lithium injection. The use of a single conditioning trial precludes possible US-induced differential orientations from influencing which stimuli will be associated on the conditioning trial. This cue-consequence specificity effect was obtained even when subjects conditioned with lithium received a non­ contingent footshock prior to the test session, and when subjects conditioned with footshock received a noncontingent lithium injection before testing (Experiments 2-4l. Weak aversions to the light in rats given a light-lithium pairing and noncontingent footshock and to the sac­ charin in subjects that received a saccharin-footshock pairing and noncontingent lithium ad­ ministration were obtained in Experiment 2. However, these weak aversions were not ob­ tained when subjects were given three nonreinforced exposures to the test chamber before the test session (Experiments 3 and 4l. These results indicate that US-induced differential orientations do not mediate the cue-consequence effect in aversion learning.

Taste aversions conditioned with intravenous copper sulfate: Attenuation by ablation of the area postrema

Borison and Wang identified the area postrema as the locus of chemoreceptors that mediate emetic reflexes elicited by blood-borne toxins. In the present experiments we have extended a systematic investigation of the afferent pathways mediating taste aversions by examining the effects of area postrema lesions on the aversions that follow either intravenous or intragastric administration of copper sulfate. Intrajugular cannulas were implanted in rats after ablation of the area postrema (Group AP-L) and in operated controls (Group AP-C). Every third day rats were offered a saccharin solution and immediately afterward were injected intravenously with 0.05 ml isotonic CuSO 4. A group of pseudo-conditioned rats (Group SAC-C) was injected with CuSO 4 approximately 24 h after ingestion of saccharin. Compared to control animals, rats with area postrema damage acquired significantly weaker aversions to saccharin when it was paired repeatedly with intravenous CuSO 4. After three conditioning trials, the rats in Group AP-L that were most resistant to acquisition of a taste aversion (Group AP-L *) were again offered saccharin, but ingestion in this case was followed immediately by intragastric injection of CuSO 4. After a single conditioning trial rats in Group AP-L * demonstrated a robust aversion. The results are discussed in terms of the parallels in afferent systems between emetic physiology and some instances of taste aversion conditioning.

One-trial backward excitatory fear conditioning in rats: Acquisition, retention, extinction, and spontaneous recovery

Water-deprived male albino rats received a single presentation of a 4-sec electric-grid-shock unconditioned stimulus followed by a 4-sec white-noise conditioned stimulus (a single backward conditioning trial.) Excitation conditioned to the noise was indexed in terms of the noise’s subsequent ability to suppress ongoing licking of a water tube. The main findings were: (1) Excitation was acquired and was retained over a 30-day retention interval; (2) although excitation was retained, it did not grow significantly stronger during the interval (there was no incubation effect); (3) excitation was extinguished by noise-alone trials; and (4) excitation showed more spontaneous recovery when extinction trials were separated by 29 days than when separated by only 1 day. Because these results are similar to those in the forward conditioning literature, they seem consistent with, but do not demand, the view that forward and backward excitatory conditioning involve similar learning processes. A current theory that embraces this view is opponent-process theory (Solomon & Corbit, 1974). We suggest that opponent-process theory can (1) account for existing backward conditioning data, (2) explain the phenomenon of incubation that has previously been described in the literature while simultaneously explaining its absence in the present study, and (3) integrate certain nonmonotonic acquisition phenomena that have appeared in both the forward and backward conditioning literatures.

Stimulus control of defensive burying in the rat

Rats shocked once through a wire-wrapped stationary prod mounted on the wall of a test chamber incorporated the bedding material covering the chamber floor into a defensive reaction. When tested 1 min later, they approached the prod and buried it. Evidence was provided by three separate studies of this burying response that rats had learned about the association of both the position and brightness of the prod with shock after this single conditioning trial. In Experiment 1, the amount of burying decreased if either the position or brightness of the prod had been changed prior to the test. In Experiments 2 and 3, rats were shocked through one of two prods (white or black) mounted on opposite walls of the test chamber. When the positions of the prods were unchanged for the test, almost every subject buried the prod through which it had been shocked, even when the conditioning-test interval was 24 hr; whereas, each rat directed substantial amounts of bedding material at both prods when the positions of the two prods were reversed. Thus, discriminated “avoidance” learning can be rapid, reliable, and enduring when shock is administered “by” a clearly defined stimulus object, i.e., when cue and consequence are spatially contiguous.

The role of handling cues in the treatment preexposure effect in taste aversion learning

Animals were injected with lithium chloride or physiological saline on four occasions prior to a single conditioning trial on which the taste of saccharin was followed by the injection of lithium chloride. On a subsequent two-bottle test for aversions to the saccharin water, it was found that animals preexposed to the lithium chloride formed weaker aversions than did animals preexposed to the physiological saline. Weakened aversions occurred independent of the amount of handling animals had experienced prior to the preexposure phase of the experiment. These findings indicated that experimenter-generated handling cues did not appear to play a role in mediating the treatment preexposure effect.

One-Trial Conditioned Suppression: Effects of Instructions on Extinction

Two experimental groups of undergraduate volunteers received a single Pavlovian conditioning trial consisting of a paired presentation of a tone conditioned stimulus (CS) and a shock unconditioned stimulus (UCS). Control groups received either the CS alone or the UCS alone. Subjects from one experimental group were subsequently instructed that they would not receive further shocks, while the other experimental group received no such instructions. The CS alone was then presented once to all four groups while subjects were engaged in a button-pressing task maintained by slide reinforcement. During the latter phase, rate of button-pressing was measured. Classically conditioned suppression of button-pressing was obtained in the noninstructed experimental group but not in the instructed group. The results demonstrate that suppression can be a sensitive index of Pavlovian conditioning in humans but question the use of conditioned suppression as an adequate experimental analog of clinically observed anxiety-motivated behavior.

Biphasic effects of nicotine upon ECS-induced retrograde amnesia in mice.

The effects of nicotine in (a) attenuating the amnesic effect of a post-conditioning electroconvulsive shock (ECS; G), (b) facilitating avoidance-response acquisition by isolation-housed mice (5), and (c) antagonizing the effects of stress effects upon memory (3) have suggested several biochemical substrates for those systems to which these actions relate. One hypothesis that has emerged from these studies is that the increased content of brain 5-hydroxytryptamine (5-HT), decrease in its turnover rate, and increase in its turnover time -as result from ECS (1, 2) can be maximally blocked by nicotine (6) given 45 min. before ECS and augmented when nicotine is administered I5 min. prior to ECS (2). O n the basis of previous behavioral findings I[ was further hypothesized that ECS-induced retrograde amnesia (which has been suggcstcd as being 5-HT-dependent) can be antagonized or potentiated depending upon [he time between nicotine treatment and a postconditioning ECS. Four groups of 30 CF-Is strain mice were given nicotine sulfate (1.0 mg.kg. i.p.) or 0.9% saline in an equivalent volume at either 15 or 45 min. prior to a single passive avoidance conditioning trial (4) followed within 10 sec. by a single transcorneal ECS (20 mA, 400 V, 200 msec.). Previous scudies (1, 2) have established that mice given no training reinforcement did not show acquisition or retention of the avoidance response and that in the absence of post-training ECS there was a high (-90%) incidence of response retention. All mice were tested for retention of the passive avoidance response 24 hr. after the training-ECS sequence. Saline-treated mice did not differ in the incidence of retrograde amnesia as a function of pre-ECS treatment time (x' = 0.11, p > 50); however, 80% of those mice treated with nicotine 45 min. before the training-ECS sequence showed criterion retention of the passive avoidance response, as compared with only 209% of the controls (x2 = 19.28, p < ,001). For the mice given nicotine 15 min. prior to [he training-ECS sequence, the incidence of conditioned response retention (10%) was less than that observed for controls (25%). Thus, the time between the administration of nicotine and ECS treatment after single-trial avoidance conditioning in mice is critical for determining whether the same dose of this drug antagonizes or potentiates the amnesic properties of such treatment. These findings are consistent with previous findings which indicate that the occurrence of rerrograde amnesia by post-training ECS depends upon alterations in cerebral 5-HT content and metabolism (2). The time course of the cerebral aminergic effens of nicotine (3) is consistent with the biphilsic requirements for temporally dependent interanion with the amnesic effect of ECS. REFERENCES 1. ESSMAN, W. B. Electroshock-induced retrograde amnesia and brain serotonin effects of several antidepressant compounds. Psychopharmacologia (Bedin), 1968, 13, 258-266.

Effects of lysine vasopressin on passive avoidance learning

On a single conditioning trial, a 1-sec electric shock (.125 or.250 mA) was administered when rats entered a darkened chamber from a lighted elevated runway. Latency to enter the chamber was recorded on retention trials given 24 and 48 h later. Animals received subcutaneous injections of varying doses of lysine vasopressin or a placebo solution immediately after the training trial or immediately before the first retention trial. Nonshocked control animals showed no increase in response latencies on successive trials, nor was there a difference between the placebo and vasopressin groups under the “no-shock” condition. Treatment with lysine vasopressin increased resistance to extinction, irrespective of the time of treatment.

ECS-induced retrograde amnesia indicated by a heart-rate measure of retention

Rats that received a single fear conditioning trial consisting of a tone followed by footshock showed marked heart-rate deceleration both during and following the presentation of the tone the next day. Groups that received either the fear conditioning trial followed by ECS, the tone followed by ECS, or neither the fear conditioning nor ECS showed little, if any, conditioned heart-rate deceleration during the test trial. These data provide evidence that ECS can effect retrograde amnesia when an autonomic index of retention is employed.

Effects of early experiences on one-trial avoidance conditioning

Female rats were either handled, shocked, or unmanipulated during the pre- or immediate postweaning period. At maturity they were observed in a one-trial avoidance situation. On the single conditioning trial, they were shocked for 1 sec or until they returned to the elevated starting platform. Thereafter, one nonshock trial per day was given for 21 days. Under the “1 sec shock” procedure, response latencies were influenced by the type of prior manipulation and the age at which it was experienced, with animals shocked during the postweaning period showing the longest latencies. Under the “variable shock” procedure, all previously manipulated groups had longer latencies than the controls.

Changes in ECS-induced retrograde amnesia with DBMC: Behavioral and biochemical correlates of brain serotonin antagonism☆

Abstract Mice treated with dimethoxy-aminoethyl-N-benzyl-M-methoxy-cinnamide hydrochloride (DBMC) 1 hr prior to being given a single conditioning trial showed a reduced incidence of retrograde amnesia induced by electroshock given following conditioning. Brain RNA and serotonin concentrations were negatively correlated in DBMC-treated mice and these animals showed a longer brain serotonin turnover time. With ECS brain serotonin concentration was slightly elevated and turnover rate was increased. The results support the hypothesis that the central changes in serotonin and RNA resulting from electroshock and the rate of memory consolidation are significantly affected by DBMC.

Electroshock-induced retrograde amnesia in seizure-protected mice.

Mice given electroshock following a single conditioning trial showed a retrograde amnesia for the conditioned response as a function of the time interval between training and electroshock. When, under two different conditions, the overt convulsion produced by electroshock was prevented, the retrograde amnesia still was in evidence. The data suggest that current flow through the brain, rather than an overt convulsion, accounts for the amnesic effect of electroshock.

Electroshock-induced retrograde amnesia and brain serotonin metabolism: effects of several antidepressant compounds.

Mice treated with either amitriptyline, nialamide, or pipradol showed a significant degree of antagonism toward the amnesic effect of electroconvulsive shock administered 10 sec following a single conditioning trial. Saline-treated control animals showed a high incidence of amnesia for the same response as a result of post-training electroshock. Under control conditions, where no posttraining ECS was given, a consistently high level of conditioned response retention was shown. Although the mechanism of action for each of the drugs with regard to serotonin metabolism was quite different, a common factor in each case was that brain serotonin levels were generally reduced following ECS, whereas for control animals one post-ECS effect was elevated brain serotonin. The present findings suggest that elevation of brain serotonin levels produced by ECS, and taking place during the post-training interval within which the memory trace is consolidated, may account, in part, for the resulting retrograde amnesia; antagonism of the amnesic effect of ECS is apparently accomplished by providing for conditions wherein this ECS-induced serotonin change is blocked.

One-trial cardiac conditioning in dogs

Our interest in cardiovascular conditioning, particularly the fact that conditional tachycardia has been observed in many dogs after only one or two combinations of conditional and unconditional stimuli, led us to investigate conditioning using a single application of an unconditional stimulus. Initially we studied the effect of orienting stimuli (soft tones) on the heart rate in 9 dogs. After 30–100 presentations of the tones alone, each dog received on one occasion a 25-volt shock (sufficient to cause yelping and struggling) to a leg as unconditional stimulus immediately following a tone. Thereafter 30–100 additional tones were presented with no further shock. Little or no heart rate change occurred during the orienting tones (before shock). Three types of cardiac changes occurred during experimental sessions after the shock: 1) Increased heart rate during the tones in 5 dogs; 2) Generalized lowering of heart rate during all experimental sessions after shock in 4 dogs; 3) Electrocardiographic changes during tones in 3 of the dogs also showing the generalized decrease in heart rate. No motor flexion conditional reflexes developed. Tones an octave different in pitch from the one associated with the shock also caused approximately the same heart rate changes, indicating lack of differentiation. This one-trial cardiac conditioning persisted after the single conditioning trial for more than a month in 2 dogs and for at least 3 to 5 sessions in the other dogs.

Spreading depression and interhemispheric transfer of an avoidance response

By the use of spreading cortical depression, an avoidance response was established in a single hemisphere in 10 rats. The interhemispheric transfer of this response could be demonstrated in 50% of the Ss following a single conditioning trial with both cortical hemispheres functional. Transfer of the response was not dependent upon the S receiving shock during this 1 trial.

Effect of tricyanoaminopropene on the amnesic effect of electroconvulsive shock.

Mice were pretreated with either tricyanoaminopropene or saline for 3 days prior to being given a single conditioning trial to establish a passive avoidance response. The training trial was followed by a single electroconvulsive shock. When tested for retention of the conditioned response 24 hrs following training, a characteristic retrograde amnesia was demonstrated in control animals, whereas experimental mice showed a significantly high degree of retention. Analysis of brain tissue from various sites, in mice treated under comparable conditions, indicated a significant elevation of levels of ribonucleic acid in the drug-treated animals, as compared with controls. The effect of ECS on RNA concentration was seen generally as a reduction, and specifically as a reduction in the magnitude of RNA concentration differences above base levels observed in non-convulsed animals. The data suggest that an acceleration of RNA synthesis with TCAP serves to facilitate memory trace formation.

Characteristics of a conditioned response in human subjects during extinction trials following a single traumatic conditioning trial.

A single experience of respiratory paralysis can be used to establish a conditioned response (CR) to a hitherto neutral stimulus. Respiratory paralysis to those undergoing it is horrific but not painful. The CR does not extinguish but becomes stronger as time passes despite repeated extinction trial