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PubMed1996

Classically conditioned motor effects do not occur with cocaine in an unbiased conditioned place preferences procedure.

Classical conditioning and behavioural sensitisation of motor activity induced with cocaine (10mg/kg, i.p.) were examined using an unbiased two-compartment conditioned place preference (CPP) procedure. Habituation of the rats to the testing environment prior to training was varied (i.e. either the rats were habituated to the environment for three 30min sessions or they were not) in order to examine a possible influence of latent inhibition on conditioned locomotion or behavioural sensitisation. Furthermore, rats were either trained with an explicit CS+ (cocaine-paired compartment) and CS- (vehicle-paired compartment), or else they were trained with no barrier between the compartments (effectively a single-compartment procedure with no explicit CS-) in order to examine a possible influence of stimulus change (training rats while confined to one compartment, but testing with no barrier between compartments). On a drug-free test day with free access to both compartments, rats previously exposed to cocaine in one compartment (CS+) and vehicle in the second compartment (CS-) spent more time in the CS+ compartment (conditioned place preference). However, under no circumstance was the rate of motor activity higher in the CS+ compartment than in the CS- compartment, as would be expected if cocaine-induced motor activity was classically conditioned to contextual cues. Whether or not increased activity extinguished with repeated drug-free exposures to previously drug-paired contexts depended on habituation experience. In addition, both habituation and current access to compartments (free or restricted) determined the presence of post-extinction sensitisation to a challenge dose of cocaine (7.5mg/kg). Classical conditioning and non-associative sensitisation, independently or together, cannot account for this pattern of results.

Journal Article↗
PubMedDate not supplied

Disrupted retention of the classically conditioned nictitating membrane response in the aluminum-intoxicated rabbit using electrical stimulation of the brain as a conditioned stimulus.

Rabbits were classically conditioned to emit an eyeblink conditioned response (CR) to electrical stimulation (ESB) of the medial geniculate nucleus (MGN) paired with a corneal air puff until they attained a criterion of two consecutive days of greater than 90% CRs. They then received intraventricular injections of 1% AlCl3, HCL, or normal saline. Ten days postinjection, each animal underwent a retention test consisting of 50 ESB alone presentations. Whereas all saline and HCL animals gave at least 90% CRs during retention, no aluminum rabbit emitted more than 30% CRs. Considered with the results of previous work, these data suggest that aluminum-induced neurofibrillary degeneration disrupts retention of the CR by affecting central associative processes.

Albinism↗
PubMed2003

Single-cue delay and trace classical conditioning in schizophrenia.

BACKGROUND: Classical conditioning provides a means of addressing mechanisms of learning and can therefore help understand the pathophysiology of memory alteration in schizophrenia. METHODS: Single cue delay and trace eyeblink conditioning were used in patients with schizophrenia and matched normal control subjects to explore, respectively, cerebellar and hippocampal integrity during learning. We measured percent of conditioned (CRs) and unconditioned responses (URs), their amplitude, and onset and peak latencies. We also accounted for spontaneous blink rates and stimulus-induced responses before learning. RESULTS: During delay conditioning, patients showed CRs with longer onset and peak latencies and improved efficiency compared to normal volunteers without there being differences between patients and normal control subjects in the percentage of CRs. During trace conditioning, neither group showed an increase in CRs as a function of conditioned stimulus-unconditioned stimulus pairings, in part because the level of spontaneous blink rates exceeded the level of CRs; however, patients with schizophrenia showed increased responding 150-400 msec after the conditioned stimulus and in the last 100-150 msec before the unconditioned stimulus, whereas normal control subjects showed only the latter type of responses. The former type of response was more frequent in patients with schizophrenia even before either trace or delay conditioning. CONCLUSIONS: These results suggest integrity of cerebellar mechanisms underlying conditioning, although the altered timing of CRs in patients may indicate differences in the modulation of such responses. Both the greater CR onset latency during delay and the presence of early nonadaptive responses during trace are compatible with the pattern of responding seen in animals with hippocampal damage.

Blinking↗
PubMed1995

Potentiation or depression of synaptic efficacy in the dentate gyrus is determined by the relationship between the conditioned and unconditioned stimulus in a classical conditioning paradigm in rats.

Learning a conditioned stimulus (CS)-unconditioned stimulus (US) association is accompanied by a variety of long-lasting changes in physiology and chemistry of the synapse in the dentate gyrus. To determine the time course of synaptic modification during learning, changes in the perforant path-dentate gyrus-evoked field potentials were measured in rats performing a classical conditioning (paired tone and footshock) or pseudoconditioning (unpaired tone and footshock) task. Over the course of 4 days of training, differential changes in the evoked response were observed in the two groups. In the conditioned group, there was an increase in the slope of the excitatory postsynaptic potential (EPSP) which started after five tone-shock paired trials and lasted for more than 40 min, outlasting the training session by 20 min. In contrast, a decrease in the slope of the EPSP which commenced after training and lasted for at least 1 h was observed in the pseudoconditioned group. In both groups there was a prolonged decrease in the amplitude of the population spike. The increase in the EPSP was reduced and the duration tended to shorten over days of training in the conditioned group, whereas in the pseudoconditioned group the decrease in the EPSP tended to increase. Off-line analysis of suppression of lever-pressing for food reward during the presentation of the tone, indicated that the conditioned rats had learned the tone-footshock association. Temperature was measured in the dentate gyrus of rats undergoing an identical procedure. In both groups slight temperature increases were observed, with no difference in amplitude and time-course between the groups. The differential effect of conditioning and pseudoconditioning on the evoked response and changes in temperature eliminate the possibility that effects of stress, arousal and muscular effort are the primary cause of the changes in the EPSP. The results suggest that behavioural events can exert bidirectional control of synaptic strength of entorhinal cortex inputs to the dentate gyrus and that the sign of synaptic modification is at least in part determined by the temporal relationship between these events. The data are discussed in terms of the type of neural activity that may mediate the processing of information in the dentate gyrus.

Animals↗
PubMed1987

Effects of a subanesthetic concentration of nitrous oxide on establishment, elicitation, and semantic and phonemic generalization of classically conditioned skin conductance responses.

Classical conditioning of skin conductance responses was studied in 16 men and 16 women breathing 30% nitrous oxide or 100% oxygen to see how nitrous oxide affected establishment, elicitation, and generalization of conditioned responses (CRs). For CRs that had been established before gas inhalation, nitrous oxide blocked elicitation of "anticipatory" (long latency) but not "orienting" (short latency) CRs. Nitrous oxide appeared to prevent new CRs from being established during its inhalation, but learning evidently took place since anticipatory CRs could be elicited after nitrous oxide inhalation had ceased. Words were used as the conditioned stimuli and nitrous oxide altered generalization of CRs to other words related in meaning or sound, though generalization effects were limited. Nitrous oxide also seemed to reduce the efficacy of the unconditioned stimulus. The results were interpreted in terms of Rescorla's theory of classical conditioning.

Adult↗
PubMed1999

Cerebellar cortical AMPA-kainate receptor blockade prevents performance of classically conditioned nictitating membrane responses.

Classical conditioning of the nictitating membrane-eye blink response of rabbits is a simple form of associative motor learning. Lesion studies have shown that performance of learned responses is dependent on the cerebellum, but they have not shown whether there is storage of memories within the cerebellum or distinguished the roles of the cerebellar cortex and nuclei. Reversible inactivations of the cerebellar nuclei have directly implicated the cerebellum in the acquisition of nictitating membrane conditioning, but previously the cerebellar cortex has not been reversibly inactivated to assess its contribution to the performance or acquisition of conditioned responses. Here we use the water-soluble disodium salt of 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) reversibly to block cerebellar cortical AMPA-kainate receptors in lobule HVI and quantitative autoradiography to map its distribution. Conditioned responses are completely, but reversibly, abolished for 10-60 min depending on the concentration of the CNQX infusion and its location within HVI. Zebrin immunohistochemistry was used to define the optimal cortical infusion site that, we suggest, corresponds to the location of the eye blink control regions. We confirm that areas in HVI are essential for the expression of classically conditioned nictitating membrane responses, and we establish a method to analyze the role of cerebellar cortex in the acquisition of this form of motor learning.

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed2006

Classical conditioning and expectancy in placebo hypoalgesia: a randomized controlled study in patients with atopic dermatitis and persons with healthy skin.

The effectiveness of placebos is unchallenged. However, it is still not clear on which mechanisms the placebo effect is based. Besides expectancy theories, classical conditioning is discussed as a major explanatory model. In an experimental conditioning design we tested 96 participants, 48 with atopic dermatitis (24 male, 24 female) and 48 with healthy skin (24 male and 24 female). All of them received a neutral ointment with a different briefing ("pain-reducing ointment" versus "neutral ointment"). Electrical pain stimuli were subsequently applied, which selectively induce a painful sensation. In the case of the learning condition (classical conditioning) and unbeknown to the participants, the intensity of the pain stimulus was reduced by 50% after the ointment had been applied. The study addressed the question whether the pain experienced by the patients with atopic dermatitis could be reduced through a placebo effect and whether the placebo effect was achieved through expectancy or through a process of classical conditioning or both. The results indicate that a placebo effect is achieved via expectancy and classical conditioning. However, conditioning processes seem to be necessary for a longer lasting effect. The extent of this effect seemed to be greater in atopics than in healthy controls. Expectancy, achieved through verbal instruction, might also be seen as a conditioned stimulus that reactivates earlier stimulus associations.

Adolescent↗
PubMed1998

Evidence of plasticity in the pontocerebellar conditioned stimulus pathway during classical conditioning of the eyeblink response in the rabbit.

Electrical stimulation thresholds required to elicit eyeblinks with either pontine or cerebellar interpositus stimulation were measured before and after classical eyeblink conditioning with paired pontine stimulation (conditioned stimulus, CS) and corneal airpuff (unconditioned stimulus, US). Pontine stimulation thresholds dropped dramatically after training and returned to baseline levels following extinction, whereas interpositus thresholds and input-output functions remained stable across training sessions. Learning rate, magnitude of threshold change, and electrode placements were correlated. Pontine projection patterns to the cerebellum were confirmed with retrograde labeling techniques. These results add to the body of literature suggesting that the pons relays CS information to the cerebellum and provide further evidence of synaptic plasticity in the cerebellar network.

Animals↗
PubMed1995

Evaluative conditioning is a qualitatively distinct form of classical conditioning: a reply to Davey (1994).

Based on a critical review of the literature, Davey (1994) [Behaviour Research and Therapy, 32, 291-299] concludes that there is no sufficient evidence to support the theoretical position that evaluative conditioning is a qualitatively different form of classical conditioning. In the present manuscript, we will try to show that Davey's conclusion is biased by: (a) an overemphasis on what he believes to be problematic procedural aspects of previous evaluative conditioning studies; and (b) a selective reading of the available evidence. Finally, an attempt is made to characterize evaluative conditioning phenomena as the output of a Referential Learning System, which can be distinguished from an Expectancy Learning System.

Association Learning↗
PubMedDate not supplied

Subcellular interactions between parallel fibre and climbing fibre signals in Purkinje cells predict sensitivity of classical conditioning to interstimulus interval.

Classical conditioning of the nictitating membrane response requires a specific temporal interval between conditioned stimulus and unconditioned stimulus, and produces an increase in Protein Kinase C (PKC) activation in Purkinje cells. To evaluate whether biochemical interactions within the Purkinje cell may explain the temporal sensitivity, a model of PKC activation by Ca2+, diacylglycerol (DAG), and arachidonic acid (AA) is developed. Ca2+ elevation is due to CF stimulation and IP3 induced Ca2+ release (IICR). DAG and IP3 result from PF stimulation, while AA results from phospholipase A2 (PLA2). Simulations predict increased PKC activation when PF stimulation precedes CF stimulation by 0.1 to 3 s. The sensitivity of IICR to the temporal relation between PF and CF stimulation, together with the buffering system of Purkinje cells, significantly contribute to the temporal sensitivity.

Algorithms↗
PubMedDate not supplied

External inhibition in a goldfish (Carassius auratus) classical conditioning situation.

Goldfish were classically conditioned with a light as the CS and shock as the US. The UR was a decrease in respiration. After 15 or 60 conditioning trials the fish were tested with novel stimuli (clicks) during the CS-US interval. High and moderate intensity novel stimuli produced a significant decrease in CRs (external inhibition) for fish with 60 conditioning trials (5.5 or 10.5 sec CS-US interval), but not fish with 15 conditioning trials. Low intensity novel stimuli produced no evidence for disinhibition (an increase in CRs). Control groups (e.g., groups with random presentations of the CS and US) showed that the external inhibition for fish with 60 conditioning trials was inhibition of a true CR.

Acoustic Stimulation↗
PubMed1990

The role of contingency in classical conditioning.

The assumption that classical conditioning depends on a contingent relation between the conditioned stimulus (CS) and the unconditioned stimulus (US), which was proposed some decades ago as an alternative to the traditional contiguity assumption, still is widely accepted as an empirical generalization, if no longer as a theoretical postulate. The first support for the contingency assumption was provided by experiments in which occasional CS-US pairings produced no response to the CS in random training--i.e., training in which the probability of the US was the same in the presence and absence of the CS. Those early experiments, the results of which too often are taken at face value, are reconsidered along with various later experiments that show conditioning, both of the CS and its context, in random training. The evidence suggests that CS-US contingency is neither necessary nor sufficient for conditioning and that the concept has long outlived any usefulness it may once have had in the analysis of conditioning.

Animals↗
PubMed1994

Classical conditioning of pain responses.

Classical conditioning is involved in the acquisition of chronic pain. The present study investigated whether experimental pain responses can be conditioned using auditory stimuli in a differential trace conditioning paradigm. 16 healthy subjects served as paid volunteers. The UCS was an intracutaneous electrical stimulus applied to the left middle-finger (10 ms duration). Tones of 1000 and 1400 Hz (both 80 dB SPL, 50 ms) were used as CS+ and CS-, respectively. A trace conditioning paradigm was used with an 800 ms interval between CS and UCS. Somatosensory event related potentials (SEP) and auditory event related potentials (AEP) were recorded from 29 electrode sites. Subjective pain reports were measured with an adjective list that allowed a detailed description of subjects' sensations elicited by painful and auditory stimuli. Data revealed significant differences of the subjective sensations between the CS+ and CS-, but no differences in the amplitudes and latencies of the P50, N100, P200, and P300 AEP components. No changes in the topographical organization of the CS+ and CS- were found. A significant differential negativity in the brain sites responsible for processing the UCS was obtained, which is attributed to the anticipation of the UCS after CS+ presentation.

Acoustic Stimulation↗
PubMedDate not supplied

Classical conditioning using vestibular reflexes.

Adaptation of the vestibulo-ocular reflex (VOR) is one of the principal models for studying motor learning in the mammalian CNS. However, there has been no previous comprehensive attempt to understand the behavioral characteristics of VOR adaptation in terms of traditional psychological learning theory. To accomplish this objective, the effectiveness of vestibular-evoked responses in serving as the conditioned or unconditioned stimulus in classical conditioning paradigms is first reviewed. Then, the various procedures for eliciting VOR adaptation are reviewed from the perspective of their similarity to standard classical conditioning protocols. A systematic analysis of Western and Russian literature yielded a relatively small number of studies that explicitly used vestibular reflexes in classical conditioning paradigms, and they report a wide range in success. Potential explanations for these diverse findings are discussed. A comprehensive categorization of the behavioral parallels between VOR adaptation and classical conditioning is then presented. Viewing VOR adaptation as a form of classical conditioning is a useful heuristic device and leads directly to the description of further behavioral experiments that could throw additional light on general mechanisms for inducing neural plasticity. Such an exercise is of benefit in order to further understand the common framework which might exist between VOR adaptation and other models of motor learning (for example, rabbit eye blink conditioning).

Animals↗
PubMed1984

The discharge characteristics of vagal cardiac neurons during classically conditioned heart rate change.

Classically conditioned heart rate change in the pigeon has been developed as a vertebrate model system for cellular analysis of associative learning. One aspect of this development involved characterizing in detail the "final common path" for the conditioned response, the "cardiac motoneurons." With this as a foundation it has been possible to investigate the discharge properties of these motoneurons during acquisition of the conditioned heart rate response, and in this paper we report such data for the vagal (parasympathetic) component of the conditioned response. The activity of single neurons was recorded in the intermediate zone of the dorsal motor nucleus of the vagus of the pigeon. Antidromic activation confirmed that these cells gave rise to efferent axons in the vagus nerve and allowed their classification on the basis of conduction velocity into three groups: A, B1 (cardiac), and B2 units. B1 and B2 units had low levels of irregularly maintained activity, whereas A units discharged more regularly at higher frequency. B1 units had a weak cardiac rhythm, no respiratory rhythm, and showed decreased discharge in response to visual stimulation or foot-shock. These stimulus-evoked decreases in the activity of cardiac cells were accompanied by increases in heart rate. B2 units were unresponsive to both visual stimulation and foot-shock, whereas A units were unresponsive to visual stimulation but possibly responsive to foot-shock. The activity of vagal cardiac neurons was recorded during or after classical conditioning (paired lights and foot-shocks) or sensitization (unpaired lights and foot-shocks) to characterize discharge changes associated with conditioned cardioacceleration.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1981

The effects of pimozide during pairing on the transfer of classical conditioning to an operant discrimination.

Transfer of classical conditioning to operant learning was demonstrated by showing enhanced acquisition of an operant discrimination in a group of rats (n = 6) previously exposed to pairings of the discriminative stimulus with food as compared to control animals (n = 6). A group (n = 6) that received the classical conditioning sessions while under the influence of the neuroleptic, pimozide (1.0 mg/kg, IP) also showed enhanced acquisition of the discrimination when tested while undrugged but their performance was intermediate between that of the other groups for the first seven sessions. For the remaining sessions, the two groups that had received classical conditioning did not differ from each other and both groups discriminated better than the controls. These data may indicate a role for dopaminergic neurons in the mechanism by which the effects of classical conditioning influence operant responding.

Animals↗
PubMed1988

Classical conditioning in a cognitive era.

Classical conditioning as a body of laboratory techniques and the phenomena which they have generated has a long history in behavioural science. Today, the emphasis on cognitive processes which has overtaken behavioural science threatens to displace the older technology. This paper examines those aspects of classical conditioning which might be expected to contribute a useful supplement to the cognitive description of human functioning. It is suggested that the emphasis on individual differences and on the modulation of affect and preference constitutes the core of this contribution.

Anxiety Disorders↗