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At least 307 records · Page 17Linked to original sources
PubMed1999

A demonstration of classical conditioning of the human eyeblink to an olfactory stimulus.

While acquisition of the eyeblink conditioned response to a variety of stimuli has been widely studied, it has yet to be established that humans will demonstrate a conditioned response to an olfactory stimulus. In this study we present data to show that humans will demonstrate a classically conditioned eyeblink response to an olfactory stimulus. Ten participants were tested in a delay conditioning procedure with an olfactory stimulus presented in a heated, humidified stream of air via an olfactometer, allowing the precise control over stimulus duration necessary for delay conditioning. Trials on which odor alone was presented were administered to four additional participants. Establishing that humans will demonstrate an eyeblink conditioned response to an olfactory stimulus will allow further exploration of the pathways involved in classical conditioning and associative learning, as well as an analysis of conditioning pathways across sensory modalities.

Adult↗
PubMed1987

Ventral tegmental area lesions do not enhance appetitive classically conditioned responses in the rat.

An autoshaping procedure, in which presentation of a retractable lever signalled food delivery, was used to assess the effects of ventral tegmental area lesions on appetitive classically conditioned responses in 28 rats. Rats with ventral tegmental area lesions did not differ from sham-lesioned rats in acquiring classically conditioned lever press responses, or in learning to withold these responses when an omission contingency was in effect. This lack of effect in an appetitive setting stands in contrast to our previous finding that aversive classically conditioned responses are facilitated by this lesion, and suggests that the ventral tegmental area lesion selectively enhances aversively motivated behaviors.

Animals↗
PubMedDate not supplied

No evidence of interference of hypocapnia/respiratory alkalosis with classical conditioning of electrodermal responses.

Most phobias can be traced to aversive experiences relating to the phobic cue, but most aversive experiences do not result in phobias. Why is it that only sometimes these experiences result in classical conditioning of fear? It was hypothesized that if the subject is in a state of hypocapnia/respiratory alkalosis, classical conditioning of fear is facilitated, while extinction of fear responses is inhibited. Thirty-two healthy volunteers underwent a classical conditioning procedure with slides as conditioned stimulus, electric shocks as unconditioned stimulus, and electrodermal responding as (un) conditioned response. During conditioning, half of the subjects hyperventilated and were hypocapnic/alkalotic, while the other half was not. In both groups clear conditioning occurred, but there was no effect of hypocapnia. Results are critically discussed.

Acid-Base Equilibrium↗
PubMed2000

Classical conditioning of oxidative DNA damage in rats.

This study investigated whether the formation of 8-hydroxydeoxyguanosine (8-OH-dG), a known oxidative DNA modification relevant to carcinogenicity, can be classically conditioned to a novel taste in order to clarify the possible role of the central nervous system (CNS) or psychological stress on cancer initiation via a classical conditioning mechanism. Male Wistar rats underwent one or two conditioned taste aversion (CTA) experiments in which ferric nitrilotriacetate (Fe-NTA), which has renal toxicity and can induce renal cell carcinoma, served as a visceral unconditioned stimulus (US), and a saccharin solution (SAC) was used as a conditioned stimulus (CS). The 8-OH-dG levels in the group conditioned with the combination of SAC and Fe-NTA significantly increased as compared to those of the uncombined groups by two repeats of the conditioning procedure (P=0.013). The rats that showed a painful response at the Fe-NTA administration had significantly higher values of 8-OH-dG than those without pain (P=0. 003). These results not only provide the first evidence regarding classical conditioning of oxidative DNA damage using the CTA procedure, but also suggest the involvement of the CNS and psychological stress in the pathogenesis of cancer via oxidative DNA damage.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed1994

Reacquisition of eyeblink classical conditioning following large cerebellar cortical lesions in Dutch belted rabbits.

The effects of cerebellar lesions on a classically conditioned eyeblink response was examined using Dutch Belted rabbits as subjects. Results confirmed our previous findings, using New Zealand White rabbits, that cerebellar cortical lesions do not abolish conditioned responding if the interpositus is intact. However, unlike our previous studies using New Zealand White rabbits, Dutch Belted rabbits failed to reach a pre-lesion level of performance. These results suggest a possible important strain difference in this paradigm.

Animals↗
PubMedDate not supplied

Brain mechanisms of extinction of the classically conditioned eyeblink response.

It is well established that the cerebellum and its associated circuitry are essential for classical conditioning of the eyeblink response and other discrete motor responses (e.g., limb flexion, head turn, etc.) learned with an aversive unconditioned stimulus (US). However, brain mechanisms underlying extinction of these responses are still relatively unclear. Behavioral studies have demonstrated extinction as an active learning process distinct from acquisition. Experimental data in eyeblink conditioning suggest that plastic changes specific to extinction may play an important role in this process. Both cerebellar and hippocampal systems may be involved in extinction of these memories. The nature of this phenomenon and identification of the neural substrates necessary for extinction of originally learned responses is the topic of this review.

Animals↗
PubMed1977

Warning signals and alerting: effects on differential classical conditioning.

Three experiments were carried out to investigate the effects of a nondifferential warning signal on differential classical conditioning. In Experiment 1, a 500-msec warning interval was found to result in good differential conditioning performance at an interstimulus interval (ISI) of 500 msec in which differential conditioning did not otherwise occur. The second experiment demonstrated the warning effect with both visual and auditory conditioned stimuli, thus ruling out the possibility that the warning effects were due to eye movements. Experment 3 showed that a warning signal and an increased ISI were functionally equivalent, as demonstrated by conditioning performance and the similar effects obtained when the ISI and warning-interval conditions were switched from optimal to nonoptimal and vice versa.

Acoustic Stimulation↗
PubMed1994

Ketamine: acquisition and retention of classically conditioned responses during treatment with large doses.

Two experiments were conducted in rabbits to examine the effects of ketamine (0, 100, and 200 mg/kg) on the acquisition and retention of the classically conditioned nictitating membrane response (NMR). Classical conditioning of the NMR was accomplished by pairing tone and light conditioned stimuli (CS) with paraorbital shock as the unconditioned stimulus (UCS). Experiment 1 assessed the effects of the drug on acquisition and retention of conditioned responses (CR) and determined the role of previous exposure to the experimental environment. Ketamine blocked the display of CR. However, data from subsequent retention testing under nondrug conditions revealed that rabbits that had previously received 100 mg/kg ketamine learned faster than saline-treated rabbits during the acquisition phases. Rabbits that received 100 mg/kg ketamine and were placed in the experimental chambers, but not presented with stimuli during the acquisition phase, did not learn faster during the retention phase than naive rabbits. Experiment 2 controlled further for the effects of nonassociative, unlearned processes. Control groups were presented with unpaired CS and UCS training after drug administration, and subsequently received conventional acquisition sessions under nondrug conditions. Their data indicated that the ketamine group's rapid acquisition during retention testing could not be attributed to nonassociative factors. We conclude that, although it was impossible directly to observe acquisition in rabbits under the influence of ketamine, it was possible that learning occurred as manifested by "savings" in subsequent learning trials.

Animals↗
PubMed1989

Acquisition of classical conditioning without cerebellar cortex.

The left cerebellar cortex was surgically aspirated in rabbits who were then subsequently trained for classical conditioning of the nictitating membrane. All rabbits were trained sequentially on both eyes. Rabbits with the lesion confined to the cerebellar cortex were able to learn with the eye ipsilateral to the lesion although it took many times longer than reported for either naive rabbits or for rabbits first trained on the unlesioned, contralateral side. Rabbits with lesions that included the cerebellar cortex and the cerebellar interpositus nucleus did not learn with the eye ipsilateral to the lesion. Learning with the eye contralateral to either type of lesion was always very rapid. It is now clear on the basis of this and previous studies that cerebellar cortex, unlike the cerebellar interpositus nucleus, is not essential for acquisition or relearning/retention of classical conditioning. However, cerebellar cortex normally plays an important role since acquisition of classical eyeblink conditioning is prolonged and of poor quality in its absence.

Animals↗
PubMed1987

Formation of new corticorubral synapses as a mechanism for classical conditioning in the cat.

An electron microscopic quantitative study of corticorubral synapses was performed in the cat which acquired classical conditioning. Conditioned stimulus was applied to the cerebral peduncle and the unconditioned stimulus was an electrical shock to the forelimb skin. The proportion of corticorubral synapses contacting with somata and proximal dendrite was increased after conditioning. It was suggested that collateral sprouting and the formation of new synapses underlie classical conditioning.

Animals↗
PubMed2006

Predicting fear of heights, snakes, and public speaking from multimodal classical conditioning events.

BACKGROUND: Two hundred fifty one men and women participated in a study of the prediction of fear of heights, snakes, and public speaking by providing retrospective accounts of multimodal classical conditioning events involving those stimuli. The fears selected for study represent those believed by some to be innate (i.e., heights), prepared (i.e., snakes), and purely experientially learned (i.e., public speaking). This study evaluated the extent to which classical conditioning experiences in direct, observational, and verbal modes contributed to the prediction of the current level of fear severity. MATERIAL/METHODS: Subjects were asked to describe their current level of fear and to estimate their experience with fear response-augmenting events (first- and higher-order aversive pairings) and fear response-moderating events (first- and higher-order appetitive pairings, and pre- and post-conditioning neutral presentations) in direct, observational, and verbal modes. RESULTS: For each stimulus, fear was predictable from direct response-augmenting events and prediction was enhanced by the inclusion of response-moderating events. Furthermore, for each fear, maximum prediction was attained by the addition of variables tapping experiences in the observational and/or verbal modes. CONCLUSIONS: Conclusions are offered regarding the importance of including response-augmenting and response-moderating events in all three modes in both research and clinical applications of classical conditioning.

Adolescent↗
PubMed1983

A cellular mechanism of classical conditioning in Aplysia: activity-dependent amplification of presynaptic facilitation.

A training procedure analogous to differential classical conditioning produces differential facilitation of excitatory postsynaptic potentials (EPSP's) in the neuronal circuit for the siphon withdrawal reflex in Aplysia. Thus, tail shock (the unconditioned stimulus) produces greater facilitation of the monosynaptic EPSP from a siphon sensory neuron to a siphon motor neuron if the shock is preceded by spike activity in the sensory neuron than if the shock and spike activity occur in a specifically unpaired pattern or if the shock occurs alone. Further experiments indicate that this activity-dependent amplification of facilitation is presynaptic in origin and involves a differential increase in spike duration and thus in Ca2+ influx in paired versus unpaired sensory neurons. The results of these cellular experiments are quantitatively similar to the results of behavioral experiments with the same protocol and parameters, suggesting that activity-dependent amplification of presynaptic facilitation may make a significant contribution to classical conditioning of the withdrawal reflex.

Action Potentials↗
PubMedDate not supplied

Age-related impairment in the 250-millisecond delay eyeblink classical conditioning procedure in C57BL/6 mice.

In this study we tested 4-, 9-, 12-, and 18-month-old C57BL/6 mice in the 250-msec delay eyeblink classical conditioning procedure to study age-related changes in a form of associative learning. The short life expectancy of mice, complete knowledge about the mouse genome, and the availability of transgenic and knock-out mouse models of age-related impairments make the mouse an excellent species for expanding knowledge on the neurobiologically and behaviorally well-characterized eyeblink classical conditioning paradigm. Based on previous research with delay eyeblink conditioning in rabbits and humans, we predicted that mice would be impaired on this cerebellar-dependent associative learning task in middle-age, at ~9 months. To fully examine age differences in behavior in mice, we used a battery of additional behavioral measures with which to compare young and older mice. These behaviors included the acoustic startle response, prepulse inhibition, rotorod, and the Morris water maze. Mice began to show impairment in cerebellar-dependent tasks such as rotorod and eyeblink conditioning at 9 to 12 months of age. Performance in hippocampally dependent tasks was not impaired in any group, including 18-month-old mice. These results in mice support results in other species, indicating that cerebellar-dependent tasks show age-related deficits earlier in adulthood than do hippocampally dependent tasks.

Acoustic Stimulation↗
PubMedDate not supplied

Simultaneous classical conditioning of two effector systems.

The experiment reported here was an attempt to develop an experimental procedure for independent classical conditioning of two different response systems, the skin conductance response (SCR) and the eyelid response. In a differential conditioning design with human subjects (N = 50) two different unconditioned stimuli were used, a white noise (US1) and airpuff (US2). Two conditioned stimuli (CS11 and CS12) were paired with US1, and two other CSs (CS21 and CS22) were paired with US2. A special trial architecture was used to accomplish measurement of both anticipatory SCR and eyelid responses during each trial. Significant eyelid differentiation as well as significant SCR (especially second interval responses) differentiation developed.

Adult↗
PubMed1975

Latent inhibition and stimulus generalization of the classically conditioned nictitating membrane response in rabbits (Oryctolagus cuniculus) following dorsal hippocampal ablation.

Rabbits received 0 to 450 exposures of a tone conditioned stimulus (CS) prior to classical defensive conditioning of the nicitating membrane response based on an infraorbital eye shock unconditioned stimulus. Tone preexposure resulted in retarded conditioning in normal rabbits. This latent inhibition effect was not present in animals with bilateral dorsal hippocampectomy produced by aspiration. Control animals with bilateral neocortical and callosal aspiration lesions demonstrated a latent inhibition effect similar to that shown by normal nonoperated animals. The failure of CS preexposure to retard conditioning in hippocampal rabbits was not due to differences in threshold of the conditioned response to the CS or to differences in response mechanisms as determined by tests of habituation and dishabituation of the unconditioned response. A subsequent experiment employed combined-cue summation tests to confirm the fact that preexposure did not endow the tone with conditioned as well as latent inhibitiory properties. Finally, tests of stimulus generalization along the auditory frequency dimension indicated flatter relative gradients for hippocampals than for nonoperated controls, with cortical controls in between. These findings were discussed in terms of Douglas' model of hippocampal function.

Acoustic Stimulation↗
PubMedDate not supplied

Are there two classes of classically-conditioned responses?

It is proposed that two response classes interact during classical conditioning: (1) a specific effect which directs responding towards or away from the CS, depending upon whether a positive or negative outcome is signaled, and (2) a general, emotional effect which interferes with responding. The interaction between these two response classes can account for the varied results obtained under CER and autoshaping procedures, and must be considered in any analysis which attempts to account for the complex nature of the conditioned response.

Animals↗