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Results for “Reversal Learning”

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At least 829 records · Page 46Linked to original sources
PubMed1976

Evidence against the response-shift account of hyperstriatal function in the pigeon (Columba livia).

Pigeons with hyperstriatal lesions and unoperated controls were given minimal or extended side-key pretraining prior to acquisition of a position discrimination. Operated birds were impaired following extended, but not minimal, pretraining. The birds then acquired a simultaneous color discrimination with posiversals of the color discrimination, operated birds were impaired, and this was primarily due to an exaggeration of perseverative responding to the former positive stimulus. Analysis of choice latencies found no tendency towards an exaggerated "Mahut effect" in hyperstriatals and indicated that operated subjects used the same solution strategies as normals. These findings directly contradict the response-shift account of hyperstriatal function and indicate a return to the response-inhibition hypothesis.

Animals↗
PubMed1981

Priming-produced facilitation or diminution of responding to a Pavlovian unconditioned stimulus.

Two experiments, concerned with signal-produced variation of unconditioned response (UR) amplitude, evaluated the roles of US intensity and response measure in determining when signaling the US results in a conditioned diminution or a conditioned facilitation of responding. In Experiment 1, rabbits received discrimination training, in an eye-blink-conditioning preparation, with a 1-mA, 50-msec shock US. In testing, preceding the US by SC+ facilitated the eye blink response compared with preceding the US by CS- or neither CS. In Experiment 2, subjects received discrimination training with a 5-mA US and were tested with 1-, 2-, and 5-mA US. During testing, subjects' eye blink responses (for which robust CRs were observed) and gross body movement responses (for which no CRs were observed) were simultaneously recorded. for the eye blink response, preceding the US by CS+ facilitated responding to the 1-mA US, produced negligible differences in responding to the 2-mA US, and diminished responding to the 5-mA US, compared with preceding the US by CS- or neither CS. For the movement response, preceding the US by CS+ diminished responding at all three US intensities, with the decremental effects increasing with increases in US intensity. The results of Experiments 1 and 2 are discussed in terms of the dual effects of CS+: the diminution of US processing and the contribution of the conditioned response to the measured response.

Animals↗
PubMed1993

Enhanced acquisition of reversal training in a spatial learning task in rats treated with chronic nimodipine.

Nimodipine levels were measured in blood and brain of rats implanted SC with sustained-release pellets of nimodipine (0, 10, 20, or 40 mg). Dose-dependent levels of nimodipine were detected in both plasma and brain. These results indicated the possible usefulness of these pellets in behavioral studies where long-term treatment is required. Therefore, the effects of chronic nimodipine, using 40-mg pellets, were examined on the performance of young, middle-aged, and aged rats in the Morris water maze. Following implantation of either nimodipine or placebo pellets, rats were trained for 6 days (three sessions/day) followed by 6 days of reversal training. During both initial and reversal training, every sixth trial was a probe trial. During initial training, there were clear age-related acquisition deficits in place training, with no effects of chronic nimodipine. Nimodipine did, however, enhance performance of rats during the first and second probe trials of reversal training. Time spent in the training quadrant by nimodipine-treated rats was approximately 30% longer on the first reversal probe and 35% longer on the second reversal probe than time spent in this quadrant by placebo-treated animals. These results indicate that chronic nimodipine enhances the performance of normal animals in reversal training on a spatial learning task.

Aging↗
PubMed2003

Perinatal exposure to diethylstilbestrol improves olfactory discrimination learning in male and female Swiss-Webster mice.

During late prenatal and early postnatal brain development, estrogen induces structural sex differences that correspond to behavioral differences in certain domains such as learning and memory. The typically superior performance of males is attributed to the action of elevated concentrations of estrogen, derived inside neurons from the aromatization of testosterone. In contrast, female performance appears dependent on minimal estrogenic activity. Rat models of the relationship between hormones and cognitive behavior predominate the field, but the advent of genetically modified mice as research tools necessitates development of analogous mouse models. This study examined how early postnatal exposure to the synthetic estrogen diethylstilbestrol (DES) affected the ability of male and female Swiss-Webster mice to learn a two-choice olfactory discrimination and three repeated reversals. Mice treated with subcutaneous injections of DES from postnatal days 1-10 learned reversals more readily than oil-treated controls, a difference that became evident after repeated testing. DES-exposed males and females learned reversals at a comparable rate, suggesting that early postnatal estrogen exposure does not influence this mode of learning through a sexually differentiated mechanism in mice. An analysis of response patterns during qualitatively different phases of reversal learning revealed that DES-induced improvements probably were not due to greater inhibitory control. Instead, DES appeared to enhance associative ability. Early postnatal estrogen exposure may have the potential to preserve certain cognitive skills in adulthood.

Animals↗
PubMed2003

Neural encoding in ventral striatum during olfactory discrimination learning.

A growing body of evidence implicates the ventral striatum in using information acquired through associative learning. The present study examined the activity of ventral striatal neurons in awake, behaving rats during go/no-go odor discrimination learning and reversal. Many neurons fired selectively to odor cues predictive of either appetitive (sucrose) or aversive (quinine) outcomes. Few neurons were selective when first exposed to the odors, but many acquired this differential activity as rats learned the significance of the cues. A substantial proportion of these neurons encoded the cues' learned motivational significance, and these neurons tended to reverse their firing selectivity after reversal of odor-outcome contingencies. Other neurons that became selectively activated during learning did not reverse, but instead appeared to encode specific combinations of cues and associated motor responses. The results support a role for ventral striatum in using the learned significance, both appetitive and aversive, of predictive cues to guide behavior.

Action Potentials↗
PubMedDate not supplied

[Ability of reversible cholinesterase inhibitors to support dissociative learning].

In the experiments on rats performed to study dissociated learning it was found that reversible inhibitors of cholinesterase are interchangeable. It was shown that neutralization of the behavioral effect of cholinesterase inhibitors may be induced most successfully by combined administration of M- and N-cholinergic blocking agents.

Animals↗
PubMedDate not supplied

The effects of structure-conformation modifications of melanotropin analogs on learning and memory: D-amino acid substituted linear and cyclic analogs.

Alpha-MSH has a wide variety of putative biological activities in addition to its classical melanocyte dispersing activity. Since each of these activities appears to be mediated by a discrete receptor, this peptide is an excellent candidate for exploring conformational restrictions which determine the chemical-physical basis for hormone action on specific activities. Experiments One and Two evaluated several cyclic and linear analogs of alpha-MSH on retrieval of memory during the reactivation of memory for a passive avoidance response following hypothermia-induced amnesia. Three of the cyclic analogs appear to have enhanced the peptide's ability to serve as a reactivation agent. One of the linear Nle4,D-Phe7 analogs antagonized whereas three others enhanced reactivation. The D-Phe7 substitution in cyclic analogs did not affect reactivation. Another group of animals were trained on a step-through passive avoidance task and tested 25 days later. The cyclic analog enhanced memory whereas the D-Phe7 analog and alpha-MSH had no effect. Finally, two analogs were tested on a black-white discrimination. Although the cyclic analog had no effect on either acquisition or reversal of this learning, the Nle4,D-Phe7 analog significantly impaired reversal learning. The results from these preliminary studies suggest that structural modifications of alpha-MSH do alter its potency and pattern of actions in learning and memory situations.

Amino Acid Sequence↗