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At least 217 records · Page 12Linked to original sources
PubMed1992

Influence of the cerebellar posterior vermis on the acquisition of the classically conditioned bradycardic response in the rabbit.

The magnitude of classically conditioned bradycardia was studied in rabbits in which various cerebellar regions (lobule IX or the posterior vermis or the hemispheres) had been removed surgically. Lesions were shown histologically to be restricted to the cortex and the underlying white matter without any damage to the deep cerebellar nuclei. In the conditioning procedure, tones were employed as conditioned stimuli (CS) and ear shocks as unconditioned stimuli (US). Cerebellar lesions did not affect the characteristics of the bradycardic orienting response, baseline heart rate or the unconditioned tachycardic response to US. The conditioned bradycardia was significantly reduced in magnitude with respect to controls in rabbits submitted to removal of posterior vermis, while it was unaffected in lobule IX and hemispheric lesioned rabbits. The temporal pattern of development and habituation of the bradycardiac response through the conditioning session, as well as its topography, did not differ from controls in any of the lesioned rabbits. After the first conditioning session, some control rabbits were submitted to removal of the posterior vermis and then conditioned again, following an identical procedure. Their pre- and post-lesion conditioned responses did not exhibit any appreciable differences and were similar to the responses exhibited by a group of unoperated controls which were submitted to a reconditioning session. It is concluded that in the rabbit the cerebellar posterior vermis is involved in the initial acquisition of the classically conditioned bradycardia, but it is not the site of its memory trace.

Animals↗
PubMed1983

Cortical evoked potential changes during classical conditioning of morphine dependence in rats.

A classical conditioning experiment was designed to determine if a conditioned neural response would develop and persist in cortical evoked potentials elicited by a foreleg stimulus (CS+) that was paired with morphine administration during the development of dependence and subsequent withdrawal. A stimulus to the other foreleg (CS-) was presented explicitly unpaired with morphine delivery. After dependence was established, the rats were taken from the experimental chamber and withdrawn from morphine for 6 days in their home cages. Finally, during the testing phase, the animals were returned to the experimental chamber and the foreleg stimuli were presented. The CS+ was paired with either morphine or saline injections. Changes due to both morphine effects only and conditioning were observed. The conditioned response, however, was present only in the cortical evoked potentials recorded from those animals receiving contralateral foreleg stimulation as the CS+. The conditioned neural response persisted after withdrawal and was present in both the drug-free and morphine-intoxicated animals. These results provide support for the relapse theory that a nonextinguished conditioned response is retained after withdrawal. However, further experiments are necessary to determine if these conditioned responses can elicit drug-seeking behavior.

Animals↗
PubMed1996

Magnetic imaging in human classical conditioning.

Magnetoencephalography (MEG) was recorded during aversive classical conditioning in an attempt to elucidate the temporal coding of primary somatosensory cortex (SI) activation previously found with positron emission tomography. Four healthy volunteers participated in the experiment. The reinforced conditioned stimulus was displayed on a screen for 2 s, and as it disappeared an unconditioned electric shock to the right middle finger followed. A control stimulus, not paired with a shock was also presented. With MEG, we observed a conditioned magnetic response located in the SI. The conditioned response predated the shock presentation and is interpreted as evidence for functional control of nociception mediated by corticothalamic projections.

Conditioning, Classical↗
PubMed1997

Magnetic brain imaging of extinction processes in human classical conditioning.

By recording neuromagnetic events during aversive classical conditioning, we examined the extinction of a previously described conditioned response. Averaging over non-reinforced exposures to the conditioned stimulus revealed magnetic activity in the secondary somatosensory and insular cortices, appearing between 110 and 140 ms after the omitted unconditioned electric shock. We suggest this activity to be elicited by the discrepancy between shock expectancy and perceptual processes associated with the omission of the unconditioned stimulus, reflecting one of several brain processes in extinction.

Adult↗
PubMed1989

Classical conditioning in patients with severe memory problems.

Classical conditioning is one of the most fundamental forms of learning, and yet little is known regarding the effects of brain injury on conditioning processes in humans. Three patients with temporal lobe lesions and severe memory problems were therefore assessed in terms of eyeblink conditioning, extinction, discrimination and reversal learning, and in one patient electrodermal conditioning was also investigated. The acquisition of conditioned responses was seen to be intact, but the evidence regarding extinction was ambiguous. All of the patients were impaired in discrimination learning and also reversal learning.

Adult↗
PubMed1991

Classical conditioning of ventilatory responses in humans.

A classical conditioning experiment, in which an auditory stimulus was paired with a hypoxic stimulus, was carried out on 34 normal subjects assigned to two groups (experimental and control). Each subject took part in one session divided into two phases, acquisition and test. In the acquisition phase, eight hypoxic and eight auditory stimuli were paired in the experimental group and unpaired in the control group. In the test phase, which was identical for the two groups, the hypoxic stimuli were suppressed and three purely auditory stimuli were presented. Significant differences between the two groups in ventilatory response to these auditory stimuli provided evidence for conditioning. In the control group, no significant changes were elicited by the auditory stimuli, whereas a conditioned increase in total cycle duration was observed in the experimental group. The conditioned response closely resembled the first component of the hypoxic response. Analysis of the pattern of the conditioned response, along with postexperimental interviews, strongly suggests that this response was not mediated by volitional factors.

Acoustic Stimulation↗
PubMed1981

Effects of haloperidol and pimozide on classical conditioning of the rabbit nictitating membrane response.

Classical conditioning of the nictitating membrane response of the rabbit was accomplished by presenting tone and light conditioned stimuli for 800 msec before delivery of the unconditioned stimulus, consisting of a 100-msec electric shock to the skin over the paraorbital region of the head. Both haloperidol (250 microgram/kg i.v.) and an equimolar dose of pimozide (308 microgram/kg i.v.) significantly retarded the rate of acquisition of conditioned responses (CRs). Control experiments conducted with separate groups of rabbits indicated that the retardant effect of haloperidol on CR acquisition was not due to an effect on sensitization, pseudoconditioning, base-line responding or the unconditioned nictitating membrane reflex. In previously trained animals, haloperidol produced a significant (12.0 ob) elevation in the intensity threshold of a tone conditioned stimulus for elicitation of CRs. In a separate group of animals, and before any conditioning, haloperidol significantly blocked the amplitude and duration of a tone-induced facilitation of the nictitating membrane reflex. It was concluded that haloperidol blocks both the conditioned and unconditioned excitatory properties of a tone and this accounts for its ability to retard the rate of CR acquisition.

Animals↗
PubMed1989

Classical conditioning in rabbits using pontine nucleus stimulation as a conditioned stimulus and inferior olive stimulation as an unconditioned stimulus.

Classical conditioning of skeletal muscle responses was accomplished by pairing microstimulation of the pontine nuclei as a conditioned stimulus (CS) with microstimulation of the dorsal accessory olive as an unconditioned stimulus (US). A conditioned response identical in form to the behavioral response elicited by the olivary stimulation was established when the CS was forward paired with the US, and behavioral extinction occurred with CS-alone presentations or unpaired CS-US presentations. Conditioned responding could not be established or maintained when the CS and US were simultaneously presented or when the US preceded the CS (i.e., backward paired). Complete lesions of the interpositus nucleus abolished both conditioned and unconditioned responses. These findings support the idea that plasticity associated with classical conditioning of skeletal muscle responses occurs in regions of the cerebellum that receive convergent CS and US input.

Animals↗
PubMed1984

The function of time discrimination and classical conditioning.

This paper makes three main points: There are many similarities between man-made rules for detecting causality and "laws" of classical conditioning, presumably generated by nature. They suggest that the function of classical conditioning resembles the detection of causality. There are twelve similarities between the clock used by rats to discriminate time and a stopwatch. They suggest that the rat's clock, like a stopwatch, was designed for measuring unknown durations. There are eight similarities between time discrimination and classical conditions. In particular, whether or not a stimulus is timed depends on the signal value of the stimulus. The similarities suggest that time discrimination and classical conditioning - their underlying mechanisms - have similar functions.

Animals↗
PubMed2005

Eyeblink classical conditioning to auditory and olfactory stimuli: performance among older adults with and without the apolipoprotein E epsilon 4 allele.

Patients with Alzheimer's disease (AD) demonstrate slowed acquisition of the conditioned response (CR) in eyeblink classical conditioning paradigms (EBCC), although it is unknown how early in the course of the disease CR acquisition is affected. This study investigated whether changes in the rate of CR acquisition were apparent in nondemented older adults at greater genetic risk for developing AD (i.e., carriers of the apolipoprotein E [APOE] epsilon 4 allele). Both epsilon 4+ and epsilon 4- participants demonstrated CR acquisition to auditory and olfactory CSs; however, rate of acquisition to the olfactory CS was significantly slower in epsilon 4+ persons. Both groups acquired the CR to an auditory CS at the same rate. Results support olfactory compromise in the earliest stages of the AD disease process. ((c) 2005 APA, all rights reserved).

Acoustic Stimulation↗
PubMed1983

Amygdala kindling in the classical conditioning paradigm.

The hypothesis was tested that epileptiform alterations of brain excitability may be elicited by a conditioning stimulus (CS) in a classical conditioning paradigm. Fifteen male albino rats were chronically implanted with electrodes in the amygdala and over the visual cortex. A train of six stroboscopic flashes served as the CS and the unconditioned stimulus was the amygdaloid electrical stimulation, delivered together with the sixth flash in the course of the kindling procedure. Rats were randomly assigned to two groups. Rats in Group 1 were exposed to one or two kindling sessions per day, and those in Group 2 were exposed to 10 such sessions every day. All rats in Group 1 showed fully mature seizures within 15 +/- 5.5 sessions, whereas none of those in Group 2 displayed kindled seizures. There was no evidence of amygdaloid afterdischarges or enhanced spiking as a response to the CS. A gradual selective suppression of the visual evoked potentials (VEP) secondary components, i.e., slow negative wave and sensory afterdischarge, paralleled kindling in Group 1. This effect was weak in Group 2. There was no change in the primary response of VEPs in either group. No recovery of VEPs followed the extinction of conditioning.

Amygdala↗
PubMed2003

Classical conditioning in the rat fetus. III. Retention, extinction, and re-activation of the conditioned response (CR).

A single paired presentation of an artificial nipple (conditioned stimulus, CS) and milk (unconditioned stimulus, US) resulted in classical conditioning. When re-exposed to the artificial nipple CS after conditioning, fetuses showed fewer oral grasp responses compared to control fetuses exposed to the milk (US) and artificial nipple (CS) in an unpaired fashion. The reduction in oral grasping was evident when the test of oral grasping was administered 18 min after conditioning but not 21 to 30 min after conditioning (Experiments 1a and 1b). Experiments 2a and 2b confirmed that nine or more exposures to the CS after conditioning, without a milk infusion, resulted in experimental extinction of the conditioned reduction in oral grasping. One re-exposure to milk during the period after classical conditioning was sufficient to re-activate memory for the association between artificial nipple CS and milk US (Experiment 3a). Fetuses exposed to one or two re-activation treatments that comprised an intraoral infusion of milk showed evidence of the conditioned reduction in oral grasping when tested after a delay sufficient to produce forgetting. Experiment 3b showed that the orosensory properties of milk were sufficient to re-activate fetal memory for the association between artificial nipple and milk. Experiment 3c indicated that central injection of 10 ng of dynorphin A 1-13 re-activated fetal memory for the classically conditioned association. Experiments 3b and 3c suggested that the orosensory properties of milk activated a kappa opioid system in the fetal brain that reduced oral grasping of the artificial nipple during the test for oral grasping.

Animals↗
PubMed1985

Lesions of the inferior olivary complex cause extinction of the classically conditioned eyeblink response.

The dentate-interpositus nuclei of the cerebellum are known to be critically involved in the production of the classically conditioned eyeblink response in the rabbit. The rostro-medial portions of the inferior olivary complex (rmIO) project to these nuclei as well as receive projections from the fifth sensory nuclei. Lesions of the rmIO caused a previously classically conditioned eyeblink response to slowly decrease in amplitude and frequency with continued paired conditioned stimulus-unconditioned stimulus (CS-UCS) training in a manner which was identical to extinction of the learned response in control animals. The lesion had no effect on the performance of the unconditioned response. Lesions of the rmIO before training prevented learning from occurring. Lesions of other portions of the IO or of the reticular formation did not specifically affect the learned response. We conclude that the rmIO is critically involved in the learning and maintenance of the classically conditioned eyeblink response. We propose that the rmIO may serve as a pathway for information from the unconditioned stimulus to reach the cerebellum, and as such may in fact be the essential reinforcing or teaching input for the learning of classically conditioned responses. These results support the hypothesis that the cerebellum contains neuronal changes which are a critical portion of the memory trace for the conditioned response.

Animals↗
PubMed2001

Selective expression of electrical correlates of differential appetitive classical conditioning in a feeding network.

Electrical correlates of differential appetitive classical conditioning were recorded in the neural network that underlies feeding in the snail Lymnaea stagnalis. In spaced training (15 trials over 3 days), the lips and the tentacle were used as CS+ (reinforced conditioned stimulus) or CS- (nonreinforced conditioned stimulus) sites for behavioral tactile conditioning. In one group of experimental animals, touch to the lips (the CS+ site) was followed by sucrose (the unconditioned stimulus, US), but touch to the tentacle (the CS- site) was not reinforced. In a second experimental group the CS+/CS- sites were reversed. Semi-intact lip-tentacle-CNS preparations were made from both experimental groups and a naive control group. Intracellular recordings were made from the B3 motor neuron of the feeding network, which allowed the monitoring of activity in the feeding central pattern generator (CPG) interneurons as well as early synaptic inputs evoked by the touch stimulus. Following successful behavioral conditioning, the touch stimulus evoked CPG-driven fictive feeding activity at the CS+ but not the CS- sites in both experimental groups. Naive snails/preparations showed no touch responses. A weak asymmetrical stimulus generalization of conditioned feeding was not retained at the electrophysiological level. An early excitatory postsynaptic potential (EPSP) response to touch was only enhanced following conditioning in the Lip CS+/tentacle CS- group but not in the Tentacle CS+/lip CS- group. The results show that the main features of differential appetitive classical conditioning can be recorded at the electrophysiological level, but some characteristics of the conditioned response are selectively expressed in the reduced preparation.

Animals↗
PubMed2001

Relation between conditioned stimulus-elicit responses and unconditioned response diminution in long-interval human heart-rate classical conditioning.

Previous research on electrodermal conditioning suggests that the conditioned diminution of the unconditioned response (UR) has an associative basis. The aim of this experiment was to test whether this phenomenon also occurs in heart rate (HR) classical conditioning. For this purpose, a differential classical conditioning was performed. The conditioned stimuli (CSs) were geometrical shapes (the CS+ was a square and the CS- was a triangle) displayed on a computer screen and a burst of white noise was used as unconditioned stimulus (US). For analysis of the conditioned response (CR) components, an interval between CS+ and US of 8 seconds was used. After the acquisition phase, participants were tested using trials with the US preceded either by a CS+, a CS-, or a neutral stimulus (a circle). The results showed conditioned diminution of the UR and suggest that the second heart rate deceleration component (D2) is responsible for the occurrence of this phenomenon.

Acoustic Stimulation↗
PubMed1989

Retention of a backward classically conditioned reflex response in spinal cat.

Retention of a backward classically conditioned reflex response was investigated in the spinal cat preparation. Facilitation of the flexion reflex was induced by the pairing of superficial peroneal nerve stimulation (30 Hz, 0.5 s), the US (unconditioned stimulus), with saphenous nerve stimulation (10 Hz, 1.5 s), the CS (conditioned stimulus). Both the US and CS were supramaximal for activation of A delta cutaneous afferent fibers. Experimental animals received 30 paired trials (US preceded CS by 0.25 s) with an intertrial interval (ITI) of three min. Control animals received the same stimuli but in an explicitly unpaired manner. Following acquisition, all animals received 30 additional CS-alone trials at five min intervals. This paradigm, which incorporated ITIs longer than those which had been used previously in backward conditioning studies, induced a long-lasting potentiation of the flexion reflex which appeared to be specific to spinal reflex pathways activated by A alpha cutaneous fibers. The relevancy of these results to a more specific understanding of backward and forward classical conditioning in the spinal cat is discussed.

Action Potentials↗
PubMed2000

Cerebellar volume in humans related to magnitude of classical conditioning.

Neural circuits in the cerebellum are essential for eyeblink classical conditioning, and hippocampal activation is also present during acquisition. Anatomical (volumetric) brain MRI, delay eyeblink conditioning and neuropsychological tests were administered to eight healthy older subjects. The correlation between cerebellar volume (corrected for total cerebral volume) and conditioned response percentage was 0.81 (p < 0.02), but neither hippocampal nor total cerebral volume correlated with conditioning or any neuropsychological test scores. There was no relationship between age and cerebellar volume, but the correlation between hippocampal volume and age was -0.80 (p < 0.02). These volumetric results add to the increasing evidence in humans demonstrating a relationship between the integrity of the cerebellum and eyeblink classical conditioning.

Aged↗