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PubMedDate not supplied

Conditional learning in aged rats: evidence of hippocampal and prefrontal cortex impairment.

Groups of normal old rats and young adult rats were administered a test of conditional discrimination learning in which different visual stimuli were associated with responses to different levers. Initially, rats were tested in a zero-delay condition in which they selected their responses in the presence of the conditional stimuli. They were later tested at 5- and 15-s delays between stimulus presentation and the appearance of the levers. Old rats were impaired in learning the basic conditional discrimination, a test thought to be sensitive to frontal lobe dysfunction. Age differences increased with the length of the interval, revealing a time-dependent memory loss that was attributed to impaired hippocampal function.

Aging↗
PubMed1984

Hippocampectomy disrupts acquisition and retention of learned conditional responding.

The effects of bilateral hippocampal and neocortical lesions were examined on acquisition and retention of classically conditioned responses based on (a) simple associations, (b) a nonconditional discrimination, and (c) a conditional discrimination in the same subjects. Results showed that combined hippocampal and neocortical damage permanently prevented (within the limits tested) both acquisition and retention of learned behavior based on the conditional discrimination but had no effect on behaviors based on the nonconditional discrimination or simple associations. Neocortical lesions alone had no effect on either conditional or nonconditional discriminative responding, but they did temporarily disrupt acquisition and retention of behavior dependent on CS-CS (two conditioned stimuli) associations. Neither lesion affected learned behaviors mediated by CS-US (conditioned stimulus and unconditioned stimulus) associations. Thus, results showed that hippocampal damage selectively disrupted learned conditional behaviors and also revealed that central nervous system control of conditional discrimination performance, within-compound associations, and CS-US associations is mediated by different neural mechanisms.

Animals↗
PubMed2001

Perirhinal cortex and place-object conditional learning in the rat.

The present study examined whether excitotoxic lesions of the perirhinal cortex can affect acquisition of a place-object conditional task in which object and spatial information must be integrated. Testing was carried out in a double Y-maze apparatus, in which rats learned a conditional rule of the type, "In Place X, choose Object A, not Object B (A+ vs. B-); in Place Y, choose Object B, not Object A (A- vs. B+)." Perirhinal cortex lesions significantly impaired acquisition of this task while sparing performance of an allocentric spatial memory task performed in a radial arm maze. Perirhinal cortex lesions also had no apparent effect on a 1-pair object discrimination task performed in the double Y maze or on retention and acquisition of 4-pair concurrent discrimination problems performed in a computer-automated touch screen testing apparatus. The results suggest that, although the perirhinal cortex and hippocampus can be functionally dissociated, their normal mode of operation includes the integration of object and spatial information.

Animals↗
PubMed1996

Role of the hippocampus plus subjacent cortex but not amygdala in visuomotor conditional learning in rhesus monkeys.

Rhesus monkeys were trained to learn a large series of visuomotor conditional associations, each involving the arbitrary coupling of a visual stimulus with 1 of 3 potentially correct forelimb movements. The monkeys then received bilateral aspiration lesions of either the amygdala plus subjacent cortex or the hippocampus plus subjacent cortex. Hippocampal but not amygdala removals significantly retarded the learning of new visuomotor associations. Neither lesion affected retention. The findings argue against a general role for the amygdala in associating information across modalities, construed broadly to include motor information. By contrast, the finding that the hippocampal formation and its subjacent cortex play a role in learning new sensorimotor associations supports the view that this region participates in the long-term storage of associative information or in the recall of recently acquired information.

Amygdala↗
PubMed1991

Hemisphere differences in conditional learning: an ERP-study.

The present ERP-experiment investigated brain asymmetry in encoding and representation of the formation of conditional associations in a Pavlovian framework. Two consonant-vowel syllables were used as conditional stimuli, one of them paired with an unconditional noise during the acquisition phase (CS+), the other never paired with noise (CS-). During a subsequent test phase, both CS cues were presented dichotically i.e. at the same time. Half of the subjects had the CS+ probe presented to the right ear (contralateral to the left hemisphere). The other half of the subjects had the CS+ presented to the left ear (contralateral to the right hemisphere). ERPs from F3, Fz and F4 leads were recorded. The paradigm used was an adaptation of the standard dichotic listening technique for the study of learned associations. The results showed that conditional associative learning occurred during the acquisition phase in both "groups". The P235 latency was furthermore delayed over the left hemisphere to the CS+ probe. During the dichotic test phase, there was a clear laterality or asymmetry effect between the groups for both the N125 and N450 components, possibly supporting an interpretation of asymmetry in encoding and cortical representation of a conditional association, although alternative interpretations remain open.

Adult↗
PubMed2005

The effect of learning condition on perceptual anticipation, awareness, and visual search.

The efficacy of explicit and implicit learning paradigms was examined during the very early stages of learning the perceptual-motor anticipation task of predicting ball direction from temporally occluded footage of soccer penalty kicks. In addition, the effect of instructional condition on point-of-gaze during learning was examined. A significant improvement in horizontal prediction accuracy was observed in the explicit learning group; however, similar improvement was evident in a placebo group who watched footage of soccer matches. Only the explicit learning intervention resulted in changes in eye movement behaviour and increased awareness of relevant postural cues. Results are discussed in terms of methodological and practical issues regarding the employment of implicit perceptual training interventions.

Adult↗
PubMed2000

Effects of pentobarbital and isoflurane on conditioned learning after transient global cerebral ischemia in rabbits.

BACKGROUND: The acquisition of a conditioned eyeblink response has been used extensively to study the neurologic substrates of learning and memory. We examined the effects of the anesthetics isoflurane and pentobarbital, or hypothermia (30 degrees C), on the ability of rabbits to acquire an eyeblink conditioned response after 6.5 min of cerebral ischemia. METHODS: New Zealand white rabbits (n = 48) were randomly assigned to sham, normothermic, hypothermic, isoflurane, or pentobarbital groups. In the normothermic, hypothermic, isoflurane, and pentobarbital groups, 6.5 min of global cerebral ischemia was produced. In animals randomized to the isoflurane and pentobarbital groups, a pattern of burst suppression was achieved on the electroencephalogram before the start of the ischemic episode. Animals in the hypothermia group were cooled to 30 degrees C before ischemia. Seven days after ischemia, eyeblink training was started using an audible tone presented for 100 ms as the conditioned stimulus. The unconditioned stimulus was an air puff directed at the cornea. The delay between the end of conditioned stimulus and the start of the unconditioned stimulus (the trace interval) was 300 ms in duration. A conditioned response was defined as an eyeblink that was initiated during the trace interval. Eighty trials per day and 15 days of training were delivered. RESULTS: Neurologic deficits were greatest in the normothermia group, and these animals also had fewer conditioned responses than those in the sham, hypothermia, or pentobarbital groups. Animals in the isoflurane group had an intermediate number of conditioned responses that was not significantly different from the normothermia group. CONCLUSIONS: This study demonstrates that a brief episode of cerebral ischemia results in the impairment of associative learning. Hypothermia and burst-suppressive doses of pentobarbital were able to improve neurobehavioral outcome as measured by ability to acquire a trace conditioned response.

Adjuvants, Anesthesia↗
PubMed2004

Psychological size and distance: emphasising the interpersonal relationship as a pathway to optimal teaching and learning conditions.

BACKGROUND: Positive interpersonal relationships between teachers and learners increase the quality of learning. The purpose of this study was to investigate psychological size (perceived status) and psychological distance (perceived emotional connectedness) in medical teaching interactions and their impact on the teaching and learning process. METHOD: A total of 45 paediatric preceptor/resident pairs engaged in longitudinal continuity training experiences at different sites were surveyed about teaching effectiveness, satisfaction with teaching, and the psychological size and distance in the relationship between each pair. RESULTS: Both residents and preceptors perceived the resident as having a smaller psychological size compared to the preceptor. Residents perceived greater psychological distance in the relationship than did preceptors, and this distance was significantly related to both residents' satisfaction with particular preceptors and their perception of the preceptors' effectiveness. CONCLUSIONS: Psychological size and distance contribute to effective and satisfactory teaching. Investigating additional aspects of the teaching-learning relationship should help identify optimal educational conditions.

Communication↗
PubMed1990

Conditioned learning in alcohol dependence: implications for cue exposure treatment.

A review of the literature pertinent to cue exposure treatment in alcohol dependence is presented. Psychological models of relapse, based on conditioning and social learning theories, are critically evaluated. In particular, attention is drawn to the potential implications for cue exposure research and treatment of an interaction between Pavlovian and operant conditioning, problems with the application of the concepts of arousal and craving and the importance of a systems model to understand physiological responses. It is concluded that no study has so far demonstrated a link between conditioned responses to alcohol-related cues and relapse, an assumption on which cue exposure treatment is based. Further, the evidence for the effectiveness of cue exposure as a treatment is lacking. Promising research directions are identified.

Alcohol Drinking↗
PubMed2005

Lack of phenotype for LTP and fear conditioning learning in calpain 1 knock-out mice.

We previously proposed the hypothesis that calpain activation played an important role in long-term potentiation (LTP) of synaptic transmission in hippocampus. Two forms of calpain are predominant in brain tissues, calpain 1 (mu-calpain), activated by micromolar calcium concentration and calpain 2 (m-calpain), activated by millimolar calcium concentration in vitro. In the present study, we tested the role of calpain 1 in LTP and in learning and memory using calpain 1 knock-out mice. Changes in learning and memory were assessed using both context and tone fear conditioning. No differences in freezing responses were observed between the knock-out and the wild-type animals during the acquisition phase of the training, eliminating the possibility that the knock-out animals could be differentially affected by the foot shock. Likewise, no differences in freezing responses elicited by either the context or the tone were observed during the retention phase. No differences in short-term potentiation (STP) or LTP were observed in hippocampal slices from the knock-out and matched wild-type mice. Several interpretations might explain these negative results. First, it is conceivable that calpain 2 plays a more dominant role in neurons, and that calpain 1 makes a minor contribution as opposed to its suspected predominant role in the hematopoietic system. Alternatively, it is conceivable that some as yet unknown compensatory mechanisms take effect, and that calpain 2 or another calpain isoform substitutes for the missing calpain 1.

Animals↗
PubMed1999

Effects of hypothermia and lamotrigine on trace-conditioned learning after global cerebral ischemia in rabbits.

Acquisition of the trace-conditioned eye blink response (CR) is mediated by a variety of brain structures, including the cerebellum, the hippocampus, and brain stem nuclei. We examined the effects of a neuronal sodium channel antagonist (lamotrigine) on the ability of rabbits to acquire an eye blink CR after 6.5 min of cerebral ischemia. New Zealand white rabbits (n = 31) were randomly assigned to sham (S), normothermic ischemia (N), hypothermic (30 degrees C) ischemia-(H), or lamotrigine (50 mg/kg) treated (L) groups. In the N, H, and L groups, 6.5 min of global cerebral ischemia was produced using an inflatable neck tourniquet. Trace conditioning was started on the 7th postischemic day. The conditioned stimulus consisted of a tone (85 dB, 6 kHz) presented for 100 ms. The unconditioned stimulus was an air puff (150 ms duration) directed at the cornea. The interval between the end of the conditioned stimulus and the start of the unconditioned stimulus (the trace interval, TI) was 300 ms in duration. A trace-conditioned response was defined as an eye blink that was initiated during the TI. Eighty trials were delivered daily for 15 days. Neurologic deficits were greatest in the N group, and these animals had fewer CRs (149 +/- 157) than animals in the S (509 +/- 214) or H (461 +/- 149) groups (P < 0.05 by analysis of variance). Animals in the L group had a total number of CRs (380 +/- 253) that was intermediate between the S and N groups. Histologic evidence of neural injury was greatest in the N group. This study demonstrates that a brief episode of cerebral ischemia results in the impairment of this test of neurobehavioral function. Both hypothermia and lamotrigine were able to attenuate the impairment of eye blink trace-conditioned responses produced by cerebral ischemia.

Animals↗
PubMed1983

Effect of naloxone on a quickly learned conditioned suppression in rats following cessation of chronic haloperidol treatment.

Rats showed marked suppression of motor activity when placed in the cage where they were previously shocked. When 14 days of consecutive administration of haloperidol was terminated, the conditioned suppression was significantly reduced. Such an effect of chronic haloperidol treatment was antagonized by pretreatment with naloxone. Thus, it is possible that the opiate-like system is involved in a part of the reduction of conditioned suppression.

Animals↗