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Results for “Conditioning, Classical”

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PubMed1989

Identified facilitator neurons L29 and L28 are excited by cutaneous stimuli used in dishabituation, sensitization, and classical conditioning of Aplysia.

Tactile or electrical stimulation of the skin can be used to produce dishabituation, sensitization, and classical conditioning of the gill- and siphon-withdrawal reflex in Aplysia. These behavioral effects are thought to involve presynaptic facilitation at the synapses from siphon sensory neurons to gill and siphon motor neurons. Facilitation of PSPs onto the motor neurons can also be produced by intracellular stimulation of single identified neurons in the abdominal ganglion, including L29 and L28. In this paper, we further characterize L29 and L28. First, we show that they are excited by cutaneous stimuli similar to those used to produce dishabituation, sensitization, and classical conditioning and may therefore participate in mediating those behavioral effects. The results are also consistent with a possible role of L29 and L28 in higher-order features of conditioning. Second, we show that 5-HT does not mimic some of the PSPs of L29, in agreement with previous evidence that L29 is not serotonergic. Third, we present 2 types of evidence that L29 acts directly to produce facilitation of the sensory cells: (1) L29 comes into close contact with sensory cells in fluorescent double-labeling experiments, and (2) L29 produces facilitation of sensory cells in dissociated cell culture. Together with the results of the preceding paper (Mackey et al., 1989), these results indicate that facilitation of sensory cell synapses contributing to behavioral enhancement of the reflex can be produced by identified neurons that use 2 different transmitters: 5-HT (the transmitter of CB1) and the unknown transmitter of L29.

Animals↗

PubMed1982

Locus coeruleus lesions and resistance to extinction of a classically conditioned response: involvement of the neocortex and hippocampus.

Bilateral electrolytic lesions of the locus coeruleus were made in rabbits prior to classical conditioning of the nictitating membrane (NM) response. After recovery, the animals received one session of unpaired training followed by 3 days of paired acquisition training and 4 days of unpaired training (extinction). At the end of extinction norepinephrine (NE) and dopamine (DA) levels were measured in several brain regions. Each lesioned animal was placed into one of two groups according to whether or not the animal exhibited a significant depletion of cortical/hippocampal NE. A third group was formed by non-lesioned controls. There were no significant differences between the 3 groups during acquisition; however, during days 3 and 4 of unpaired extinction the group with cortical/hippocampal NE depletion showed significantly larger NM responses on the conditioned stimulus-alone trials than either of the two control groups. This extinction deficit appeared mainly in the unconditioned stimulus-period component of the tone-alone conditioned responses. The magnitude of the extinction deficit was highly correlated with the depletion of NE in both cortical and hippocampal samples but not with the depletion of NE in the hypothalamus/mid-thalamus, or cerebellum.

Animals↗

PubMed1986

Hippocampal lesions disrupt classical conditioning of cross-modality reversal learning of the rabbit nictitating membrane response.

The role of the hippocampus and subiculum in classical conditioning of tone-light discrimination reversal learning of the rabbit nictitating membrane response was investigated using aspiration lesions of both limbic structures. Only two of seven animals with hippocampal-subicular damage successfully reached reversal criteria within 21 days of conditioning, although all hippocampectomized animals learned the initial discrimination at rates equivalent to those of two control groups. Thus, previously reported deficits in two-tone reversal learning seen after similar lesions are not due to increased within-modality generalization to the conditioned stimuli (CS) serving as the CS+ and CS-.

Animals↗

PubMed1985

Differential effects of hippocampectomy on classically conditioned rabbit nictitating membrane response related to interstimulus interval.

The effects of hippocampal ablation on acquisition rates and temporal characteristics of classically conditioned nictitating membrane responses were examined in groups of rabbits trained with a 150-, 300-, or 600-ms interstimulus interval. Acquisition rates were accelerated in the 150- and 600-ms groups. No effect was present in the 300-ms group. Response onset latencies were also affected in the 150-ms group. These findings were interpreted to support the notion that the hippocampus modulates learned motor behavior by a neural model of the response to be executed.

Animals↗

PubMed2006

Experimental challenges to theories of classical conditioning: application of an attentional model of storage and retrieval.

Several studies have recently challenged the accuracy of traditional models of classical conditioning that account for some experimental data in terms of a storage deficit. Among other results, it has been reported that extinction of the blocking or overshadowing stimulus results in the recovery of the response to the blocked or overshadowed stimulus, backward blocking shows spontaneous recovery, extinction of the training context results in the recovery from latent inhibition, interposing a delay between conditioning and testing in latent inhibition increases latent inhibition, and latent inhibition antagonizes overshadowing. An existing neural network model of classical conditioning (N. A. Schmajuk, Y. Lam, & J. A. Gray, 1996), which includes an attentional mechanism controlling both storage and retrieval of associations, is able to quantitatively describe these results.

Animals↗

PubMed1990

Increases in glutamate release and phosphoinositide metabolism associated with long-term potentiation and classical conditioning.

Long-term potentiation (LTP) is a widely studied model of the kind of activity-dependent modulation of synaptic efficacy which is assumed to provide the physical basis for learning. Whether LTP, in the hippocampus or elsewhere in the brain, does in fact serve such a role is still a matter for debate. One approach to answering this question is to identify physiological or biochemical changes which are common to both learning and LTP; in the hippocampus, for example, one can ask whether the biochemical changes associated with LTP are also associated with learning. In this chapter we summarize the results which we have obtained in a study of glutamate release and phosphoinositide turnover in the dentate gyrus of rats trained in a classical conditioning task. The similarity between the changes occurring after classical conditioning and those associated with LTP is consistent with the hypothesis that LTP is one of the mechanisms by which a neural trace of the learned association is formed. We discuss this interpretation in the light of the observation that classical conditioning does not appear to affect synaptic responses in the hippocampus.

Animals↗

PubMedDate not supplied

Facilitated acquisition of the classically conditioned eyeblink response in male rats after systemic IL-1beta.

Exposure to inescapable stressors enhances cue-dependent learning in male rats; enhanced learning is apparent as facilitated acquisition of the classically conditioned eyeblink respouse (CCER). The proinflammatory cytokines, in particular interleukin (IL)-1beta, are presumed to orchestrate a number of acute-phase stress responses in rats, most notably fever, reduced feeding, and inactivity. Little is known of the impact proinflammatory cytokines have on learning and memory processes. Here, we address the effects of IL-1beta treatment on acquisition of the classically conditioned eyeblink response 2 hours [?] after injection in male rats. Training was accomplished with a delay-type paradigm (500-ms conditional stimulus coterminating with a 10-ms periorbital unconditional stimulation). Facilitated acquisition was clearly apparent in rats treated with IL-1beta (3.0 microg/kg). In a second experiment, we compared rats treated with 3.0 microg/kg to those treated with 1.0 microg/kg. Facilitated acquisition was reproduced, but the lower dose did not appreciably affect acquisition. These data further support contentions that IL-1beta has anxiogenic properties, affecting basic new motor learning in a manner similar to that observed after exposure to stress.

Animals↗

PubMedDate not supplied

Classically conditioned hyperglycemia in the obese mouse.

The obese (C57BL/6J ob/ob) mouse is a commonly used animal model of non-insulin-dependent diabetes mellitus. It has recently been demonstrated that this mouse is not consistently hyperglycemic, however, unless it is subjected to environmental stress. In the present study, hyperglycemia in obese mice was induced by classical conditioning. Obese diabetic mice and lean control animals were exposed to shaking stress. All animals developed hyperglycemia in response to shaking. To demonstrate classical conditioning, some obese and lean animals were exposed to a metronome prior to and during the shaking. Other animals were exposed to the metronome and shaking in a noncontingent fashion and one group of animals was exposed to the metronome without any exposure to shaking. All animals received seven exposures to one of the three above conditions over a 3-day period. On the 4th day all animals were exposed to the metronome alone, following which blood samples were drawn. Classical conditioning of stress hyperglycemia was demonstrated in obese, but not in lean, mice.

Animals↗

PubMedDate not supplied

Reinforcement in an in vitro analog of appetitive classical conditioning of feeding behavior in Aplysia: blockade by a dopamine antagonist.

In a recently developed in vitro analog of appetitive classical conditioning of feeding in Aplysia, the unconditioned stimulus (US) was electrical stimulation of the esophageal nerve (En). This nerve is rich in dopamine (DA)-containing processes, which suggests that DA mediates reinforcement during appetitive conditioning. To test this possibility, methylergonovine was used to antagonize DA receptors. Methylergonovine (1 nM) blocked the pairing-specific increase in fictive feeding that is usually induced by in vitro classical conditioning. The present results and previous observation that methylergonovine also blocks the effects of contingent reinforcement in an in vitro analog of appetitive operant conditioning suggest that DA mediates reinforcement for appetitive associative conditioning of feeding in Aplysia.

Animals↗

PubMed1993

Cerebellar cortical lesions and reacquisition in classical conditioning of the nictitating membrane response in rabbits.

Portions of cerebellar cortex, particularly Larsell's hemisphere VI, have been identified as involved but not essential for the acquisition and retention of classical conditioning of the nictitating membrane (NM) response in rabbit. The present experiment was undertaken to examine the effect of lesions of cerebellar cortical regions projecting to anterior dorsolateral interpositus nucleus. Lesions of relatively equal size, including hemisphere VI and additionally more medial, anterior, or lateral cerebellar cortex were made after rabbits were classically conditioned. The effect of these cerebellar cortical lesions on retention to tone versus light conditioned stimulus (CS) and the timing of the conditioned response was evaluated. In spite of relatively large cerebellar cortical lesions, reacquisition of the conditioned NM response occurred quite rapidly. Whether the lesion was more medial and anterior or more lateral did not affect retention. Retention was significantly poorer with light CS than with tone CS. Timing of CRs was not affected by these lesions of cerebellar cortex, but the lesions spared most of the anterior lobe. The parasagittal zone C3 covering the longitudinal band of tissue from anterior lobe to the paramedian lobule and projecting to dorsolateral anterior interpositus requires additional exploration for its role in classical NM conditioning.

Animals↗

PubMed1994

Electrophysiological evidence for formation of new corticorubral synapses associated with classical conditioning in the cat.

The present study was performed to clarify whether or not structural plasticity of synaptic connections underlies classical conditioning mediated by the red nucleus (RN) in the cat. Conditioned forelimb flexion is established by pairing electrical conditioned stimuli (CS), applied to corticorubral fibers at the cerebral peduncle (CP), with a forelimb skin shock (the unconditioned stimulus, US), but not by applying the CS alone or by pairing the CS and US at random intervals. In our previous study, it was shown that the firing probability of rubrospinal neurons (RN neurons) in response to the CS was well correlated with acquisition of the conditioned forelimb flexion and that the primary site of neural change underlying establishment of the conditioned forelimb flexion was suggested to be at corticorubral synapses. In the present study, we investigated corticorubral excitatory postsynaptic potentials evoked by CP stimulation (CP-EPSPs), in order to identify the neuronal mechanism underlying establishment of classical conditioning. In normal cats, CP-EPSPs had a typical slow-rising phase, which has been attributed to the distal location of corticorubral synapses on the dendrites of RN neurons. In contrast, in animals that received paired conditioning, subsequent CP stimulation evoked potentials with a fast-rising time course. In control groups of cats that received CS alone, CS randomly paired with the US, or only the same surgical operations as the conditioned animals, most of the CP-EPSPs displayed slow-rising EPSPs that similar to those observed in normal cats. The mean time from onset to peak of the potentials in the conditioned animals was significantly shorter than that seen in other groups. Therefore, the appearance of a fast-rising potential correlates well with acquisition of the conditioned forelimb flexion. The amplitude of the fast-rising potential was gradually changed with stimulus intensity. It had a short onset latency following CP stimulation (0.9 ms), which was similar to that of the slow-rising EPSP in normal cats. It followed high-frequency stimulation up to 100 Hz. These results suggest that the newly appearing, fast-rising potential was a monosynaptically evoked EPSP. Fast-rising EPSPs were also induced by stimulation of the sensorimotor cortex (SM). Since the SM-EPSP was occluded by the CP-EPSP, the SM cortex is, at least in part, a likely source of fast-rising EPSPs. Fast-rising SM-EPSPs were also observed at the unitary level. The SM-EPSPs in the conditioned animals exhibited somatotopical representation in their cortical origin, as has been described in normal cats.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1982

Simulation of anticipatory responses in classical conditioning by a neuron-like adaptive element.

A neuron-like adaptive element is described that produces an important feature of the anticipatory nature of classical conditioning. The response that occurs after training (conditioned response) usually begins earlier than the reinforcing stimulus (unconditioned stimulus). The conditioned response therefore usually anticipates the unconditioned stimulus. This aspect of classical conditioning has been largely neglected by hypotheses that neurons provide single unit analogs of conditioning. This paper briefly presents the model and extends earlier results by computer simulation of conditioned inhibition and chaining of associations.

Animals↗

PubMed2002

Medial prefrontal cortex early lesion effects on classical conditioned bradycardia.

The effects of medial prefrontal cortex early lesion (mPFl) on classical conditioned bradycardia (CB) were studied in adult rabbits. In lesioned rabbits, baseline HR, orienting and conditioned HR responses were similar to controls. Since mPFl alone does not affect CB, while it is known to prevent the HR increments produced by a concomitant early cerebellar vermal ablation, medial prefrontal cortex must be involved in the reorganization of the CB control mechanisms following early cerebellar vermal ablation.

Animals↗

PubMed1985

Classical conditioning of a flexor nerve response in spinal cats: effects of tibial nerve CS and a differential conditioning paradigm.

Previous studies have shown flexor nerve response increases produced by classical conditioning procedures in spinal cats when the conditioned stimulus (CS) was delivered to the superficial peroneal nerve and the unconditioned stimulus (US) was delivered to the ankle skin. In this study, these effects were produced when the CS was delivered to the whole tibial nerve or to the medial plantar branch. The finding that response increases followed by extinction effects could be obtained when either the superficial peroneal or the tibial nerve was utilized allowed the assessment of the effects of a differential conditioning paradigm. The responses to CS-US presentations on the superficial peroneal nerve increased, whereas responses to CS presentations on the tibial nerve remained unchanged. However, lack of extinction effects in the superficial peroneal data suggested that stimulation of the tibial nerve potentiated superficial peroneal evoked responses. Furthermore, responses evoked by stimulation of either nerve increased when paired trials were given on the tibial nerve. These data demonstrate that stimulation of the tibial nerve potentiates responses to superficial peroneal nerve stimulation but that superficial peroneal nerve stimulation has no effect on responses to CS presentations to the tibial nerve.

Animals↗

PubMed1992

Classic conditioning and placebo effects in crossover studies.

OBJECTIVE: To find evidence of classically conditioned placebo effects in a placebo-controlled crossover drug study. Specifically, we tested a prediction of the conditioning model that the placebo response will be greater after drug exposure than before. METHODS: Twenty-four patients with mild to moderate essential hypertension and no contraindications to atenolol participated in the study. The study design required randomized assignment to one of three groups: placebo followed by 50 mg atenolol daily, followed by no treatment, each for 1 week; atenolol followed by placebo; and atenolol followed by nothing (to show residual drug effects). Twice-daily blood pressure measurements were made by patients at home; once-weekly measurements of blood pressure and heart rate were made by a research nurse. RESULTS: Before drug treatment, there were no differences in the antihypertensive responses of patients taking placebo and patients taking nothing (difference, 0.98 mm Hg; 95% confidence interval, -0.98 to 2.93). After atenolol treatment, placebo treatment produced a significantly greater antihypertensive response than no treatment (difference, -6.09 mm Hg; 95% confidence interval, -11.81 to -0.38). Thus the placebo response after atenolol administration was more than a residual drug effect. Similar patterns were observed for heart rate but not for blood pressure readings taken in the office. CONCLUSIONS: These observations are consistent with a conditioning model of placebo effects. These findings warrant further investigation in larger studies and in other disease models.

Adult↗

PubMed1990

Classical conditioning of vascular responses in mild hypertensives and normotensives.

Using a discriminative classical conditioning paradigm, this study addresses the question of whether vascular responses are more easily acquired or slower to extinguish in mild hypertensives than in normotensive controls. We subjected 18 mild hypertensives, with a resting systolic/diastolic blood pressure of 141/100 mmHg, and 17 normotensive controls similar in age, with resting systolic/diastolic blood pressure 122/80 mmHg, to a discriminative Pavlovian conditioning paradigm with tones of 8 s duration serving as conditioned stimuli (CS) and a mild electric shock as an unconditioned stimulus (UCS). Digital finger pulse volume (FPV) responses were recorded during an acquisition phase, where CS+, but not CS-, was repeatedly paired with the UCS (12 trials), and an extinction phase where shocks were withheld (12 trials). During the acquisition phase, mild hypertensives displayed greater anticipatory vasoconstrictive responses both to CS+ and CS- compared with normotensive controls. In addition, unconditioned FPV responses were enhanced in mild hypertensives. During the extinction phase, mild hypertensives evidenced increased resistance to extinction since conditioned vasoconstriction was more frequently observed in response to CS+ than to CS- in mild hypertensives only. Thus, vascular dysregulation in mild hypertensives was evident both for unconditioned and conditioned vasoconstriction. Data are compatible both with a centrally determined increased conditionability in mild hypertensive compared with normotensive and with a decreased threshold for peripheral vascular responsiveness among mild hypertensives.

Adult↗

PubMed1980

Classical conditioning of kindled seizures.

As a model of reflex epilepsy, rats were classically conditioned to show paroxysmal spike activity to an auditory stimulus. A tone stimulus was paired with seizures induced by kindling. After repeated pairings, paroxysmal discharges were elicited at tone onset. The duration of the tone, proximity to the stimulation, and the number of pairings appeared to be important in the conditioning process.

Acoustic Stimulation↗

PubMed1991

Olfactory classical conditioning in neonates.

One-day-old, awake infants underwent an olfactory classical conditioning procedure to assess associative learning within the olfactory system of newborns. Experimental infants received ten 30-second pairings of a novel olfactory conditioned stimulus (a citrus odor of neutral value) and tactile stimulation provided by stroking as the reinforcing unconditioned stimulus (a stimulus with positive properties). Control babies received only the odor, only the stroking, or the stroking followed by the odor presentation. The next day, all infants, in either the awake or sleep state, were given five 30-second presentations of the odor. Results were analyzed from video tapes scored by an observer unaware of the infants' training condition. The results indicate that only those infants who received the forward pairings of the odor and stroking exhibited conditioned responding (head turning toward the odor) to the citrus odor. The performance of the conditioned response was not affected by the state of the baby during testing, because both awake and sleeping infants exhibited conditioned responses. Furthermore, the expression of the conditioned response was odor specific; a novel floral odor presented during testing did not elicit conditioned responses in the experimental babies. These results suggest that complex associative olfactory learning is seen in newborns within the first 48 hours of life. These baseline findings may serve as normative data against which observation from neonates at risk for neurological sequelae may be compared.

Conditioning, Classical↗