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Results for “Reversal Learning”

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PubMed1975

Faster acquisition of an olfactory discrimination following septal lesions in male albino rats.

Normal rats and rats with septal lesions were maintained on a 23.5-hr water deprivation schedule and trained to bar press for water reinforcement, which was available during the presentation of one odor (SD) but not another (Sdelta). Vanilla and vinegar were the olfactants. Both groups showed evidence of discrimination within the first 2-hr of training and reached asymptotic discrimination ratios greater than 90 percent, but the rats with septal lesions reached successively higher levels of discrimination faster than the controls. The results suggest a septal inhibitory influence on the olfactory bulbs.

Animals↗
PubMed1981

GABAergic modulation of learned helplessness.

Previous studies have demonstrated the GABAergic system in the hippocampus to be a major controlling factor in the reversal of learned helplessness by antidepressants. In the present work, animals in which learned helplessness (LeH) was induced by exposure to uncontrollable electric shock demonstrated a decreased depolarization-induced release of GABA relative to controls, and an increased release of hippocampal glutamate. Injection of bicuculline but not glutamate into the hippocampus produced a behavioral state identical to that induced by uncontrollable shock, but had no influence on pain sensitivity. When flux through the "small" hippocampal pool of GABA was determined, chronic treatment with imipramine or iprindole, but lorazepam or chlorpromazine elevated this measure. These three findings along with those of prior experiments, suggest a controlling role for GABA in the learned helplessness model of depression.

Amino Acids↗
PubMed1997

Dietary gluten and learning to attend to redundant stimuli in rats.

The purpose of the present study was to assess the effect of a high-gluten diet against a gluten-free diet on learning stimulus-response relationships in rats. In the first phase of training rats learned to associate a stimulus light with responding on a particular response lever. In the second phase, the same rats were exposed to new, but redundant stimuli to guide responding (a tone and houselight). Probe trials, involving only new stimuli, revealed that rats fed a gluten-free diet displayed a "blocking" effect. That is, gluten-free rats did not learn to associate these new stimuli with particular responses. In contrast, high-gluten rats very quickly learned to use these redundant stimuli to guide responding. Subsequent phases of training demonstrated, however, that this group difference could be removed. The present findings are discussed in the context of the possible links between dietary gluten and schizophrenia.

Acoustic Stimulation↗
PubMed2003

Conditional discrimination learning in patients with bilateral medial temporal lobe amnesia.

The ability of bilateral medial temporal lobe amnesic patients (MT; n=8) and normal participants (NC; n=8) to acquire a conditional discrimination in trace and delay eyeblink conditioning paradigms was investigated. Experiment 1 assessed trace conditional discrimination learning by using a light conditional stimulus (S+/S-) and tone conditioned stimulus (CS) separated by a 1-s trace. NCs responded differentially on S+ trials (mean percent conditioned responses=66) versus S- trials (30). Whereas MTs were impaired in their acquisition of the conditional discrimination (S+ =51, S- =43). In Experiment 2, the temporal separation was eliminated. NCs acquired the conditional discrimination (S+ =70, S- =29). MTs were unable to respond differentially (S+ =42, S- =37). The findings indicate that the hippocampal system is essential in acquiring a conditional discrimination, even in a delay paradigm.

Adult↗
PubMed1990

Hierarchical structures: chunking by food type facilitates spatial memory.

Three experiments assessed the ability of male Sprague-Dawley rats to organize the spatial locations of different food types in a hierarchical manner to maximize the efficiency of working memory. Independent groups were exposed, on a 12-arm radial maze, to baiting arrangements varying in the stability of the pattern and type of food used as bait. Training rats with stable, differentiable baiting arrangements produced increased accuracy in choice performance, hierarchically ordered patterns of choice selection, slower growth of proactive interference when trials were massed, and the learning of the geometrical relations among food types independent of other extramaze cues. Such findings are strong evidence of the rat's ability to encode and use local cues for navigation, based on properties of the reinforcer. The application of a chunking strategy may provide for more efficient use of working memory by facilitating information storage, recall, or resetting mechanisms.

Animals↗
PubMed2002

Visual discrimination learning and strategy behavior in the fat-tailed dunnart (Sminthopsis crassicaudata).

Fat-tailed dunnarts (Sminthopsis crassicaudata) were trained on visual discrimination learning-set, reversal-set, and spatial delayed-alternation tasks. The learning set involved 36 2-way black-and-white pattern discriminations and 5 probe reversals. Ten reversals of a black-and-white pattern discrimination were followed by 5 novel tasks. Spatial alternation was tested at delays up to 20 s. Learning-set and reversal-set formation, including 1-trial learning and spontaneous transfer from learning set to reversals and vice versa, was found. Learning-set-experienced dunnarts showed no retention of previously learned tasks 1 week after testing but demonstrated consistently high Trial 2 performance, indicating the retention of a response strategy. Delayed-alternation tasks were learned up to 10-s delays. These results provide the first evidence of a visually guided "win-stay, lose-shift" strategy in a marsupial.

Analysis of Variance↗