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PubMedDate not supplied

Varying temporal location of a conditioned stimulus in heart rate conditioning of Macaca mulatta.

The several functions that a stimulus can assume were investigated in a Pavlovian conditioning procedure. The subjects were six rhesus monkeys; the response under observation was heart rate. The conditioning began with a temporal separation of zero between a signal and a regularly repeating electric shock; the signal was then moved to a series of earlier locations in the inter-shock interval. After six sessions at each location, two sessions followed in which only the shock was delivered periodically. The findings included: (1) A two-phased conditioned cardiac rate response seen at the first location became more multiphasic and irregular during longer intervals between signal and shock; (2) the location where the conditioned response peaked became increasingly variable as the signal was moved back, but this variability maintained a constant proportion to the signal-shock interval; and (3) heart rate during a presignal period, and during a comparable period in shock only sessions, was generally deceleratory early in training and acceleratory thereafter. Sessions with the signal showed heart rate in the presignal period to have become acceleratory earlier in training than sessions with shock only. The data pertain to stimulus control over heart rate as a function of: (A) the temporal proximity of a signal to an aversive stimulus; and, (B) the presence or absence of the signal. The use of appropriate response units in cardiac conditioning is also discussed.

Animals↗
PubMed2000

Classically conditioned withdrawal reflex in cerebellar patients. 1. Impaired conditioned responses.

The role of the cerebellum in the classically conditioned, human lower-limb-withdrawal reflex was studied in ten patients with pure cerebellar diseases (CBL), ten patients showing additional extracerebellar symptoms (CBL+), and in 11 sex- and age-matched normal controls (CTRL). Where conditioning was successful, the electrically evoked, unconditioned response was preceded by a tone-conditioned response (CR). CR incidence was variable, with best results in the CTRL, significantly less in CBL, and lowest in CBL+. Although CRs could be established in subjects in all groups, a continuous increase in the CR incidence in the course of the recording session was observed primarily in CTRL. In CBL and CBL+, such a characteristic reflex acquisition was rather the exception. CR onsets in CBL were within the range of those in CTRL, but CR amplitude was significantly lower in CBL. Cerebellar patients with circumscribed lesions behaved differently in our motor-learning paradigm, depending on the lesion site. Patients suffering from pathology of the posterior inferior cerebellum showed a mean CR incidence within the lower range of CTRL. In contrast, if the anterior and superior cerebellum was affected, few or even no CRs were observed. Our findings thus provide evidence that the human cerebellum is required for the acquisition and the retention of this specific conditioned limb-withdrawal reflex. In particular, anterior and superior parts of the cerebellum appear to be involved. Thus, an expansion of the current concept of clinically based, functional compartmentalization is suggested, such that anterior and superior cerebellar regions must be intact to establish plastic changes required for the acquisition of the conditioned withdrawal response.

Adult↗
PubMed1982

Biogenic monoamine turnover in discrete rat brain regions is correlated with conditioned emotional response and its conditioning history.

The content and turnover of dopamine, norepinephrine and 5-hydroxytryptamine (serotonin), and the content of their respective major metabolites were evaluated in 19 discrete brain areas of rats exposed to conditioned emotional response (CER), and in control groups which received either equivalent yoked shock (shock only) or compound stimulus presentation (tone only). On test day, CER animals suppressed responding and exhibited forms of emotional behavior after presentation of the conditioned stimulus (CS); while shock only and tone only control groups, and CER animals which received an acute dose of diazepam prior to testing, did not suppress. Few changes were observed in content of the biogenic amines or their metabolites, suggesting that the behavioral manipulations were acting within normal physiological limits. On the other hand, numerous changes were observed in the utilization of the 3 biogenic monoamines, which were correlated with the conditioning-anxiety (comparisons of CER vs shock only) and the shock history (comparison of shock only vs tone only). These observations are consistent with putative neural pathways in the frontal cortex, septum, nucleus accumbens, amygdala, striatum, hippocampus and brain stem (which utilize specific monoamines), and with discrete brain areas which have been implicated in classical conditioning and CER-related phenomena. These observations suggest roles for biogenic monoamines in mediating or responding to the classical conditioning and emotional components of the paradigm.

Animals↗
PubMed1984

Influence of conditioned stimulus context on hyperglycemic conditioned responses.

Glycemic conditioning was investigated in four experiments in which insulin was administered to animals in particular stimulus contexts. Both hyperglycemic and hypoglycemic conditioned responses were obtained, with the directionality of the CR dependent upon which environmental complex was used as the CS. These bidirectional glycemic CRs were obtained in both within-Subject and between-Subject conditioning procedures. Additional experiments indicated that the hyperglycemic CR was probably not related to illumination differences between the two conditioning contexts, nor to a differential opportunity for activity in the two conditioning contexts. Several possible reasons for the occurrence of bidirectional glycemic CRs were considered.

Animals↗
PubMed1994

Glucose- and fructose-conditioned flavor preferences in rats: taste versus postingestive conditioning.

Flavor preferences conditioned by glucose and fructose were compared using two training methods. With the simultaneous method preferences can be reinforced by the flavor and/or the postingestive consequences of nutrients, whereas with the delayed method preferences are reinforced only by postingestive nutritive effects. In Experiment 1, food-deprived rats displayed similar preferences for flavors (CS+) added to an 8% glucose or 8% fructose solution over flavors (CS-) added to a noncaloric saccharin solution (simultaneous conditioning). Other rats learned to prefer a CS+ flavor paired with the delayed (10 min) presentation of 8% glucose over a CS- flavor paired with delayed saccharin. Fructose failed to condition a flavor preference with the delayed paradigm. Taken together, these data suggest that the preference for a flavor mixed in a fructose solution is reinforced by the sweet taste, not the postingestive effects of the sugar. Experiment 2 tested this idea by devaluing the taste of the sugar solutions by quinine adulteration. Rats initially avoided both glucose-quinine and fructose-quinine solutions in favor of a saccharin solution. Following one-bottle training, they came to prefer the glucose-quinine but not the fructose-quinine solution over the saccharin solution. The glucose-trained rats also showed stronger preferences for sucrose-quinine solutions than did the fructose-trained rats. These findings, along with other recent data, indicate that fructose-conditioned preferences are based primarily on the sugar's palatable taste. Glucose, in contrast, can condition strong preferences based on its taste as well as its postingestive actions.

Animals↗
PubMed1990

Haloperidol impairs classically conditioned nictitating membrane responses and conditioning-related cerebellar interpositus nucleus activity in rabbits.

Rabbits, chronically implanted with recording electrodes in the cerebellar interpositus nucleus and following acquisition of a classically conditioned eyelid response, were injected with haloperidol (HAL, 250 micrograms/kg). HAL significantly reduced the number of conditioned responses when a 75 and 85 dB tone conditioned stimulus (CS) was presented but not when a 95 dB tone CS was used. There was a corresponding decrease in interpositus activity at the 75 and 85 dB CS intensities but not at the 95 dB intensity. HAL appeared to disrupt CRs and interpositus activity by increasing the intensity threshold of the tone CS for eliciting conditioned responses. Possible mechanisms for the effect of HAL on neural circuitry involved in classical eyelid conditioning are discussed.

Animals↗
PubMed1990

Effects of conditioned stimulus pre-exposure on human electrodermal conditioning to fear-relevant and fear-irrelevant stimuli.

The effects of conditioned stimulus (CS) pre-exposure and fear-relevance of the CS on human Pavlovian electrodermal conditioning were investigated. A differential delayed conditioning paradigm was used with a CS-unconditioned stimulus (US; shock) interval of 8 s. In Experiment 1, 64 subjects were randomized into four groups, two of which received fear-relevant stimuli and the other two fear-irrelevant stimuli. Half of the subjects were pre-exposed to the to-be-CSs and the other half to two not-to-be-CSs, with 15 exposure of each stimulus. During acquisition, subjects received 8 reinforced and 8 nonreinforced CS+ and CS- trials, and during the extinction phase 15 nonreinforced trials of each CS. Pre-exposure to the to-be-CSs retarded conditioning for the first and second interval anticipatory responses (FIRs and SIRs); that is, a latent inhibition effect was demonstrated, although the results for the FIR were inconclusive. The expected effects of fear-relevance were not revealed. Experiment 2 addressed the question whether the long pre-exposure period interfered with the frequently observed "preparedness effect" of higher resistance to extinction to fear-relevant stimuli. The design was similar to that of Experiment 1, but for half of the subjects the acquisition phase was initiated immediately after a short rest period, and for the other half acquisition started after an extended rest period, equal to the duration of the pre-exposure phase in Experiment 1. Twenty extinction trials of each CS were presented. A reliable difference in arousal in terms of spontaneous fluctuations was produced by the rest periods, but although differential conditioning was observed, no effect of fear-relevance was seen during extinction.

Adolescent↗
PubMed1992

Distribution of c-fos expression in brainstem neurons associated with conditioning and pseudo-conditioning of the rabbit nictitating membrane reflex.

Experiments were performed to test the hypothesis that there is a characteristic distribution of neuronal c-fos expression associated with the classical conditioning of the rabbit nictitating membrane reflex (NMR). Rabbits were divided into two groups: a conditioning group that received paired tone and airpuff stimuli in a traditional delay NMR conditioning paradigm and a pseudo-conditioning group in which the same number of tone and airpuff stimuli were applied but without being paired. Labeling was present in similar brainstem nuclei in both groups of animals. The labeled sites included trigeminal and auditory nuclei in the classical pathway for the nictitating membrane reflex as well as other nuclei such as the raphe nuclei and those in the ventrolateral medulla (VLM). However, there were quantitative differences in the labeling between the two groups. There were significantly more labeled nuclear profiles in the trigeminal nucleus of the pseudoconditioned rabbits, but more labeled nuclear profiles in the raphe nuclei in the conditioned animals. Interestingly, the ratio of the labeling in the raphe versus the VLM strongly differed between the two groups.

Animals↗
PubMed2004

Excitatory backward conditioning in an appetitive conditioned reinforcement preparation with rats.

Four experiments were conducted to examine appetitive backward conditioning in a conditioned reinforcement preparation. In all experiments, off-line classical conditioning was conducted following lever-press training on two levers. Presentations of a sucrose solution by a liquid dipper served as an unconditioned stimulus (US) and two auditory stimuli served as conditioned stimuli (CSs); one was paired with the US in either a forward (Experiment 1a) or a backward (Experiments 1b, 2, and 3) relationship, and the other served as a control CS, which was not paired with the US. In testing, each lever-press response produced a presentation of one of the CSs instead of appetitive reinforcers. The response to a lever was facilitated, compared to the response to another lever, when the response produced the backward CS presentation as well as when it produced the forward CS presentation; that is, the backward CS served as an excitatory conditioned reinforcer.

Animals↗
PubMed2003

Effects of dorsal striatum lesions in tone fear conditioning and contextual fear conditioning.

It has been suggested that the striatum mediates hippocampus-independent memory tasks. Classical fear conditioning to a discrete stimulus such as a tone is not affected by hippocampal lesion, whereas contextual fear conditioning is an hippocampus dependent task. The purpose of the present study was to verify the effect of dorsal striatal lesions on tone and contextual fear conditioning. The lesioned rats were not impaired in contextual fear conditioning but in tone fear conditioning both electrolytically and neurotoxically lesioned animals showed less freezing compared with controls. The lesion effect was observed after a postoperative recovery period of 14 days but not after 2 months. The results support the hypothesis that the dorsal striatum is involved in hippocampus-independent memory tasks, but, in spite of this involvement, it does not seem to be a critical structure.

Acoustic Stimulation↗
PubMed2001

The development of olfactory conditioned ejaculatory preferences in the male rat. II. Parametric manipulation of conditioning session number and duration.

We have previously demonstrated that repeated pairing of a neutral odor with copulation produces a subsequent conditioned ejaculatory preference (CEP) for females bearing that odor. The present study examines the course of CEP development. In Experiment 1, Long-Evans male rats were allowed access to almond-scented, sexually receptive females for either one, five, or nine conditioning sessions that were 30 min in duration. Males given five or nine sessions displayed significant CEPs. In Experiment 2, male rats were given a single conditioning session with multiple almond-scented females until either a duration (60, 120, 180, or 240 min) or copulatory criterion (two, four, or six ejaculatory series) was satisfied. Males that received 120-, 180-, or 240-min sessions or four ejaculations displayed significant CEPs; males that received two or six ejaculations displayed a trend for CEPs. Analysis of effect size estimates revealed that the strongest CEPs were produced by 120 min of copulation or four ejaculations. In Experiment 3, males receiving nine conditioning sessions each 30 min in duration displayed a more enduring CEP than did males receiving a single conditioning session 240 min in duration. These data suggest that early sexual experiences have particularly powerful influences on subsequent sexual preferences and that the development of sexual preferences are influenced by interactions between CS-UCS pairings and motivational variables.

Animals↗
PubMed1989

Conditioned orienting (alpha) and delayed behavioral and evoked neural responses during classical conditioning.

A differentiation of short-latency (alpha) and long-latency (delayed) classically conditioned behavioral and evoked neural (hippocampal) responses was attempted. Further, facilitation and retardation of these responses were studied in an experimental design in which 10 paired conditioning sessions either preceded (CC-CO group) or followed (CO-CC group) 10 randomly unpaired presentations of conditioned stimuli (CS) and unconditioned stimuli (UCS). A 2024-ms tone (1000 Hz) was delivered directly through a miniature earphone to the left ear, eliciting an orienting head movement ('alpha' response) to the left. The unconditioned stimulus (UCS) was a direct 1024-ms stimulation of the lateral hypothalamic area overlapping the CS (delayed paradigm) so that both stimuli terminated simultaneously. The UCS elicited approach behavior and a specific head movement in each animal. The latency and the direction of the head movement were used as criteria for a differentiation of the short-latency and long-latency conditioned responses (CR). All cats showed conditioned short-latency responses. Pairing specific long-latency head movements were observed in 10 of 13 cats and 6 of them showed a long-latency CR which was a head movement to the right, while the short-latency CR on the same trials was a head movement to the left. Hippocampal (subiculum, dentate fascia and CA1) evoked responses also showed pairing specific CRs appearing as increased negativity (short-latency CR), or increased positivity (long-latency CR). Additional reversed stimulus order (backward) sessions supported an assumption of the different nature of the short-latency and long-latency CRs: the long-latency CRs showed extinction while the short-latency CRs remained. The unpaired pre-exposure to the CSs and UCSs in the CO-CC group resulted in the retarded acquisition of the behavioral responses during the subsequent paired sessions.

Animals↗
PubMed1998

Lesions of the midline thalamic nuclei impair classical conditioning under partial but not continuous reinforcement conditions.

Rabbits with lesions of the midline thalamic nuclei were compared to rabbits with sham lesions on classical eyeblink (EB) and heart rate (HR) conditioning. Separate groups of sham and lesioned animals received either 25, 50 or 100% reinforcement with a periorbital shock unconditioned stimulus. Animals with lesions showed slightly impaired EB conditioning, compared to sham animals, under the partial but not continuous reinforcement schedules. Midline lesions also reduced the magnitude of the decelerative HR conditioned response under partial but not continuous reinforcement conditions. These findings suggest that the midline thalamic nuclei, like the mediodorsal nucleus of the thalamus, process information required for response selection under non-optimal learning conditions.

Animals↗
PubMed1997

Conditioned inhibition of autonomic Pavlovian conditioning in humans.

The present study aimed to demonstrate conditioned inhibition of Pavlovian conditioning of autonomic responses in humans. Subjects (N = 21) were presented initially with four geometric shapes (A, B, C and D). An electric shock served as the unconditioned stimulus (US) during acquisition. Conditional stimuli lasted for 8 s and US onset coincided with CS offset. Subjects were trained with A-US, C-US, and AC-US pairings and AB alone and B alone presentations. The subsequent summation test consisted of C-US pairings and CB alone and CD alone presentations. Conditioning was evident in self-reported US expectancy and first and second interval electrodermal responses. Evidence for conditioned inhibition during the summation test was found in US expectancy and second interval electrodermal responses.

Adolescent↗
PubMed1985

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

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.

Animals↗
PubMed2000

Evaluative conditioning in the picture-picture paradigm with random assignment of conditioned stimuli to unconditioned stimuli.

Human participants were allocated to 1 of 3 groups. In the conditioning group, each conditioned stimulus (CS)-unconditioned stimulus (US) pair was presented 7 times during the acquisition phase. Participants who were assigned to the extinction group saw 5 additional presentations of each CS in isolation after the 7 presentations of each CS-US pair. In the latent inhibition group, the CS-only trials were presented before the CS-US trials. Overall, a significant evaluative conditioning effect was observed. This effect cannot be dismissed on the basis of the arguments developed by A. P. Field and G. C. L. Davey (1997, 1998, 1999), and the results thus provide strong evidence for the associative nature of evaluative conditioning. The results are also in line with other findings, which showed that evaluative conditioning is resistant to extinction.

Conditioning, Classical↗
PubMed1978

A role for conditioned stimulus duration in toxiphobia conditioning.

The effect of conditioned stimulus (CS) exposure duration on toxiphobia conditioning was investigated. When a relatively long (20--30 min) CS exposure was administered on the conditioning trial, rats subsequently displayed a reduced conditioned aversion in comparison with when CS exposure was relatively brief (5--10 min). This result was obtained in an odor-aversion learning task with neonatal rats as subjects (Experiments 1 and 2) and in a flavor-aversion learning task with adult rats (Experiment 3). This phenomenon was further investigated in the odor-aversion task by presenting neonates with two discrete 10-min exposures to the odor CS and by varying both the temporal proximity of the two CS presentations to each other and to the occurrence of the unconditioned stimulus (US). Two exposures to the CS reduced conditioning in comparison with a single exposure but only when the second CS presentation preceded US occurrence by at least 5 min (Experiments 4 and 5). Both nonassociative and associative interpretations of the data were discussed.

Age Factors↗
PubMed1981

Contextual conditioning and the US preexposure effect in conditioned fear.

A series of five experiments was carried out in which fear of context caused by exposure to shocks was manipulated by signaling the shocks with a discrete stimulus, signaling the days during which shocks occurred with a session-long stimulus, or switching the context between exposure and the subsequent test. All these manipulations influenced fear of the context in the manner predicted by the Rescorla-Wagner associative model. Following this, all the rats were given conditioning trials with shock and a different discrete stimulus. All preexposure treatments produced consistent and reliable interference with conditioning with the exception of signaling the shocks with a discrete stimulus, which greatly reduced interference. These results are interpreted as being consistent both with a cognitive explanation of the US exposure effect, which claims that animals learn that shocks are unpredictable during conditioning and this knowledge retards future conditioning when they are predictable, and with an adaptation explanation, which claims that unpredictable shocks produce chronic fear and this fear through either a change in adaptation level or through emotional exhaustion renders the shocks less reinforcing during the conditioning test.

Adaptation, Psychological↗