Hippocampal theta-band activity and trace eyeblink conditioning in rabbits.

The authors examined the relationship between hippocampal theta activity and trace eyeblink conditioning. Hippocampal electrophysiological local field potentials were recorded before, during, and after conditioning or explicitly unpaired training sessions in adult male New Zealand White rabbits. As expected, a high relative power of theta activity (theta ratio) in the hippocampus predicted faster acquisition of the conditioned response during trace conditioning but, contrary to previous results obtained using the delay paradigm, only in the initial stage of learning. The presentation of the conditioned stimulus overall elicited an increase in the hippocampal theta ratio. The theta ratio decreased in the unpaired group as a function of training, remained high throughout conditioning in the fast learners, and rapidly increased in the slow learners initially showing a low theta ratio. Our results indicate a reciprocal connection between the hippocampal oscillatory activity and associative learning. The hippocampal theta ratio seems to reflect changes and differences in the subjects’ alertness and responsiveness to external stimuli, which affect the rate of learning and are, in turn, affected by both conditioning and unpaired training. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Nicotinic cholinergic system involvement in eyeblink classical conditioning in rabbits.

A nicotinic cholinergic antagonist, mecamylamine (MEC), was administered to rabbits tested on eyeblink classical conditioning (EBCC) in the 750-msec delay paradigm for 10 90-trial sessions. Nicotinic receptors were measured in 3 brain regions in S treatment groups: paired conditioned stimulus–unconditioned stimulus (CS–UCS) presentations with (1) vehicle, young; (2) vehicle, older; (3) 0.5 mg/kg MEC, young; unpaired CS–UCS with (4) 0.5 mg/kg MEC, young; and (5) vehicle, young. Daily MEC injections disrupted acquisition in young rabbits (769 trials to learning criterion vs 323 trials for vehicle-treated young rabbits). MEC-treated young rabbits learned similarly to older rabbits. Brain nicotinic receptors were not affected by 10 daily MEC injections. To our knowledge, this experimental protocol, using a low MEC dose to selectively inhibit nicotinic cholinergic receptors, is the first to demonstrate a role for nicotinic cholinergic receptors in EBCC. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Decremental effects of context exposure following delay eyeblink conditioning in rabbits.

The conditioning context arises from the relatively static features of the training environment. In rabbit eyeblink conditioning, procedures that retard acquisition (conditioned stimulus [CS] preexposure, unconditioned stimulus preexposure, blocking manipulations) are attenuated by context changes. In this article the authors investigate the effect of context exposure after initial delay conditioning. After conditioned responses (CRs) were established, one group received 6 sessions of context exposure, whereas control groups either remained in their home cages or received exposure to handling and a novel context. Thereafter, all groups received CS-alone testing. The expression of CRs was substantially reduced following context exposure relative to any retention loss in the home-cage control. Exposure to handling and a novel context facilitated the CRs rather than reducing them. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hippocampal activity during classical discrimination—Reversal eyeblink conditioning in rabbits.

Multiple-unit neuronal recordings were taken from the hippocampi of 10 male, New Zealand white rabbits during classical discrimination and reversal eyeblink conditioning using 2 tones as the conditioned stimuli (CS+ and CS–) and an air-puff unconditioned stimulus. During discrimination training, characteristic learning-related activity was seen in the hippocampus on trials when a conditioned response (CR) was executed. During early phases of reversal training, however, when high numbers of CRs were evident to both the new CS+ (the former CS–) and the new CS– (the former CS+), no learning-related activity was observed. Characteristic CR-related hippocampal activity to the CS+ was observed only after the rabbits began to learn the reversal response. These results suggest that the hippocampus may encode different features of eyeblink conditioning during discrimination and reversal learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Exploration of cerebellar-dependent associative learning in schizophrenia: Effects of varying and shifting interstimulus interval on eyeblink conditioning.

Eyeblink conditioning abnormalities have been reported in schizophrenia, but the extent to which these anomalies are evident across a range of delay intervals (i.e., interstimulus intervals; ISIs) is unknown. In addition, the effects of ISI shifts on learning are unknown, though such manipulations can be informative about the plasticity of cerebellar timing functions. Therefore, the primary purpose of the present study was to investigate the interactions between ISI manipulations and learning in schizophrenia. A standard delay eyeblink conditioning procedure with four different interstimulus intervals (ISIs; 250, 350, 550, 850 ms) was employed. Each eyeblink conditioning experiment was immediately followed by another with a different ISI, thus permitting the characterization of conditioned response (CR) learning at one ISI and the extent to which CRs could be generated at a different latency following an ISI shift. Collapsing across all conditions, the schizophrenia group (n = 55) had significantly fewer conditioned responses and longer onset latencies than age-matched controls (n = 55). Surprisingly, shifting to a new ISI had negligible effects on conditioned response rates in both groups. These findings contribute to evidence of robust eyeblink conditioning abnormalities in schizophrenia and suggest impaired cerebellar function, but underscore the need for more research to clarify the source of these abnormalities and their relationship to clinical manifestations of schizophrenia. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Examination of bilateral eyeblink conditioning in rats.

This experiment monitored eyelid responses bilaterally during delay eyeblink conditioning in rats. Rats were given paired or unpaired training with a tone or light conditioned stimulus (CS) and a unilateral periorbital shock unconditioned stimulus (US). Rats given paired training acquired high levels of conditioned responses (CRs), which occurred in both eyelids. However, acquisition was faster, and the overall percentage of CRs was greater in the eyelid that was ipsilateral to the US. CRs in the eyelid ipsilateral to the US also had shorter onset latencies and larger amplitudes than CRs in the contralateral eyelid. Both eyelids consistently showed high percentages of unconditioned responses (UR) to the US, and the UR amplitude decreased across training sessions in the paired group. The present study demonstrated that CRs occur robustly in both eyelids of rats given eyeblink conditioning, which is similar to previous findings in humans and monkeys. The results also showed that conditioning occurs more prominently in the eyelid that is ipsilateral to the US, which is similar to previous findings in humans, monkeys, dogs, and rabbits. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Discriminated lateralized eyeblink conditioning in the rabbit: An experimental context for separating specific and general associative influences.

Four experiments demonstrated discriminated lateralized eyeblink conditioning in 38 male rabbits and showed how the phenomenon may be used to differentiate between the reflexive and emotive consequences of Pavlovian conditioning. Exps 1, 2, and 3 characterized how 2 conditioned stimuli (CSs), contemporaneously trained with left vs right paraorbital unconditioned stimuli (UCSs), can produce different CRs, each involving predominant closure of the eye ipsilateral to its UCS. Exp 4 showed how the associative tendencies controlled by additional stimuli could be evaluated by presentations in compound with such discriminanda: A 30-sec stimulus, presumed to acquire a conditioned emotional response but no eyeblink CR, equally potentiated the eyelid CRs elicited by both CSs. A 1,050-msec CS that evoked an eyeblink CR in isolation also increased the responding to both CSs but biased it toward its own lateralized CR. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cerebellar involvement in eyeblink classical conditioning in humans.

The role of the ipsilateral cerebellum in human eyeblink conditioning was investigated using the 400-ms delay paradigm and testing 14 cerebellar patients (7 with unilateral lesions and 7 with bilateral lesions) and 20 control participants. Patients performed significantly worse with the ipsilesional eye than control participants but showed no difference when tested with the contralesional eye. Conditioned responses (CRs) totaled 14% for all patients in comparison with 60% for control participants. Data on timed-interval tapping for 6 patients and 14 control participants showed that clock variability was greater with the ipsilesional hand in patients. Only clock variability correlated significantly with percentage of CRs in control participants. Comparisons of paired associate learning and memory for 8 patients and 14 control participants revealed no significant differences. Results confirm that the ipsilateral cerebellum plays a role in eyeblink classical conditioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cortical involvement in acquisition and extinction of trace eyeblink conditioning.

Previous studies have implicated 2 cortical regions interconnected with the hippocampal formation, the retrosplenial cortex (RSQ and the medial prefrontal cortex (mPFC), as loci important for the acquisition of hippocampally dependent trace eyeblink conditioning. These loci have also been proposed to serve as long-term storage sites of task critical information. This study used lesions made prior to training to investigate the roles of the RSC, as well as the caudal and rostral subdivisions of the mPFC, in the acquisition and subsequent extinction of trace eyeblink conditioning in the rabbit. The caudal mPFC and rostral were shown to be critical for acquisition and extinction of the conditioned reflex, respectively. The data indicate that the RSC is not critical for acquisition or extinction of the trace conditioned reflex. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Prefrontal control of trace eyeblink conditioning in rabbits: Role in retrieval of the CR?

Rabbits (Oryctolagus cuniculus) were trained on a trace eyeblink (EB) conditioning task to a criterion of 10 consecutive EB conditioned responses (CRs). One week later, ibotenic acid or sham lesions were made in the mPFC centered on the prelimbic region (Brodmann's area 32) or the cingulate cortex (Brodmann's area 24). Following a 1-week postoperative recovery period, all animals were retrained for 4 consecutive days using the same parameters as during acquisition, given 1 week off, and retrained for another 4 days. Mean EB conditioning deficits in the group with area 32 lesions occurred on the first and second days of each retraining period. However, by the third and fourth days of retraining, these lesioned animals were performing at a level comparable to that of the sham group. Lesions of area 24 did not produce deficits at either retesting period. These findings were interpreted to indicate that area 32, but not area 24, is involved in retrieval processes, rather than consolidation or storage, in that the animals were impaired at both retesting times, but were able to relearn the task. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reflex facilitation during eyeblink conditioning and subsequent interpositus nucleus inactivation in the rabbit (Orycotolagus cuniculus).

In eyeblink conditioning in the rabbit (Oryctolagus cuniculus), not only is a conditioned response (CR) acquired, but also the original reflex is modified as a function of training. In Experiment 1, by comparing unconditioned responses in unpaired and paired groups, 3 types of reflex facilitation were distinguished. One type was linked to exposure to the unconditioned stimuli (USs) and/or experimental setting. The 2nd type was related to the formation of the memory trace for conditioned eyeblink. The 3rd type was linked to the conditioned stimulus immediately preceding the US in the paired group. In Experiment 2, reversible inactivation of the interpositus nucleus (IPN) abolished the CR and reduced the CR-related reflex facilitation, indicating that the latter depends on the plasticity of the IPN. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attentional and error-correcting associative mechanisms in classical conditioning.

R. A. Rescorla (2000, Rescorla, 2001, Rescorla, 2002) reported that the associative changes undergone by 2 conditioned stimuli that are reinforced or not reinforced in compound depend on their initial associations. The results contradict the predictions of simple error-correction models but can be explained by models that incorporate a “constrained” error-correction rule. A model of classical conditioning presented by N. A. Schmajuk, Y. Lam, and J. A. Gray (1996) suggests that attentional mechanisms, acting during both compound training and testing, have an important role in producing those results. Moreover, the model suggests that those attentional mechanisms might obscure the evaluation of the associative changes undergone by the conditioned stimuli during compound training. Two experiments that differentiate our model from competing theories are proposed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Trace eyeblink conditioning in the freely moving rat: Optimizing the conditioning parameters.

Trace eyeblink conditioning (EBC) parameters, with an airpuff unconditioned stimulus, were examined in male Fischer 344?×?Brown Norway F1 rats. Integrated electromyographic activity from the upper eyelid was recorded. An 8-kHz tone was superior to white noise as a conditioning stimulus. Rats trained with 30 or 50 trials per session showed similar learning. Reversal of environmental lighting had no significant effect. Trace intervals of 0 and 250 ms yielded well-timed conditioned responses (CRs); intervals of 500 ms or more did not. These experiments provide parameters that reliably yield CRs and suggest limits on the temporal processing capabilities of the rat. EBC can thus be used as part of a comprehensive test battery for learning and memory in this species. Physiological recording and pharmacological manipulations may also be done easily. This combination of approaches should facilitate a more complete understanding of learning mechanisms and age-related memory impairments. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effects of aging in delay and trace human eyeblink conditioning.

Normal aging has been shown to impact performance during human eyeblink classical conditioning, with older adults showing lower conditioning levels than younger adults. Previous findings showed younger adults can acquire both delay and trace conditioning concurrently, but it is not known whether older adults can learn under the same conditions. Present results indicated older adults did not produce a significantly greater number of conditioned responses during acquisition, but their ability to time eyeblink responses prior to the unconditioned stimulus was preserved. The decline in eyeblink conditioning that typically accompanies aging has been extended to concurrent presentations of delay and trace conditioning trials. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Awareness in classical differential eyeblink conditioning in young and aging humans.

The role of awareness and its impact on learning the conditioned eyeblink response was investigated in both trace and delay discrimination eyeblink conditioning in young and aging participants, in 4 paradigms: delay 750, delay 1250, trace 500, and trace 1000. Participants concurrently watched a silent movie about which they were questioned afterward. Acquisition in both the trace and delay discrimination task was correlated with awareness of conditioning stimulus contingencies, regardless of age. Age-dependent deficits were observed in trace discrimination but not in delay discrimination, with more severe deficits appearing at the longer trace interval. The percentage of aware participants was also found to be greater in the young population than in the aging population. These results indicate that awareness or knowledge of stimulus contingencies may be an important contributor to successful acquisition in higher order discrimination tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Standard delay eyeblink classical conditioning is independent of awareness.

P. F. Lovibond and D. R. Shanks (see record 2002-00340-001) suggested that all forms of classical conditioning depend on awareness of the stimulus contingencies. This article considers the available data for eyeblink classical conditioning, including data from 2 studies (R. E. Clark, J. R. Manns, & L. R. Squire, 2001; J. R. Manns, R. E. Clark, & L. R. Squire, 2001) that were completed too recently to have been considered in their review. In addition, in response to questions raised by P. F. Lovibond and D. R. Shanks, 2 new analyses of data are presented from studies published previously. The available data from humans and experimental animals provide strong evidence that delay eyeblink classical conditioning (but not trace eyeblink classical conditioning) can be acquired and retained independently of the forebrain and independently of awareness. This conclusion applies to standard conditioning paradigms; for example, to single-cue delay conditioning when a tone is used as the conditioned stimulus (CS) and to differential delay conditioning when the positive and negative conditioned stimuli (CS+ and CS-) are a tone and white noise. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Delay discrimination and reversal eyeblink classical conditioning in abstinent chronic alcoholics.

[Correction Notice: An erratum for this article was reported in Vol 23(2) of Neuropsychology (see record 2009-02621-003). The lifetime drinking data listed in Table 1 on p. 198 was not correctly calculated and underestimated lifetime exposure to alcohol. The corrected lifetime variables from that table are included.] Evidence has shown that alcoholism leads to volume reductions in brain regions critical for associative learning using the eyeblink classical conditioning paradigm (EBCC). Evidence indicates that cerebellar shrinkage causes impairment in simple forms of EBCC, whereas changes in forebrain structures result in impairment in more complex tasks. In this study, the ability of abstinent alcoholics and matched control participants to acquire learned responses during delay discrimination and discrimination reversal was examined and related to severity of drinking history and neuropsychological performance. During discrimination learning, one tone (CS+) predicted the occurrence of an airpuff (unconditioned stimulus), and another tone (CS-) served as a neutral stimulus; then the significance of the tones was reversed. Alcoholics who learned the initial discrimination were impaired in acquiring the new CS+ after the tones reversed; this is a function that has previously been linked to forebrain structures. It is suggested that a factor important to alcoholic addiction may be the presence of alcoholic-related associative responses that interfere with the ability to learn new more adaptive associations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Number of trials to assess human eyeblink classical conditioning.

Eyeblink classical conditioning ( EBCC) is a useful paradigm for studying the neurobiology of learning and memory. EBCC shows large age effects and has been shown to be sensitive to Alzheimer-like neuropathology. The EBCC data of 241 participants, including young, middle-aged, and elderly normal adults, adults with Down's syndrome, and patients with probable Alzheimer's disease, were analyzed to identify a minimum number of trials for reliable assessment. Results indicate that EBCC performance can be as reliably assessed in 63 trials as in 90 trials. Using fewer conditioning trials reduces administration time, making EBCC more practical for both research and potential diagnostic purposes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)