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Results for “Reversal Learning”

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At least 1,369 records · Page 76Linked to original sources
PubMed1980

Presentation rate and the representation of briefly glimpsed pictures in memory.

Four experiments on memory for briefly presented complex pictures showed the following: (a) Pictures shown in a sequence for 110 msec each with a blank 5,890-msec interstimulus interval (ISI) were later recognized almost as well as pictures shown for 6 sec each with no ISI; (b) when the ISI was deleted, recognition memory for the briefly presented pictures dropped almost to chance; (c) however, filling a 5-sec ISI with a to-be-ignored picture that was the same on all trials had little or no effect on memory for the briefly presented pictures; (d) when the time between 110-msec pictures was decreased from 4,890 to 1,390, 620, 385, or 0 msec, the ability to detect that they were mirror reversed in the recognition test decreased more rapidly than did recognition accuracy. Evidently, incidental visuospatial properties of a picture can be encoded for at least 1 sec after a brief presentation unless another to-be-remembered picture is presented during that time.

Attention↗
PubMed1978

Operativity and reversibility in children's understanding of pictorial sequences.

The role of reversibility in children's comprehension and memory for sequences of pictures was investigated. Bidirectionality in the ability to remember and infer antecedents and consequences was assessed. Preschoolers were significantly more accurate at identifying consequences of portrayed events than the antecedents. Kindergartners and older children correctly identified beginnings and endings of sequences with equal proficiency. This developmental shift from relatively unidirectional to reversible comprehension was observed both on trials involving figurative memory and operative inference judgments.

Child↗
PubMedDate not supplied

[Effect of sensory and motivational factors on monkey frontal cortex neuron activity].

In chronic experiments on rhesus monkeys formation of new neuronal response patterns appeared when the delay was prolonged or the side of the rewarded conditioned movement changed. This process was accompanied with changes in the background unit activity during response elaboration. Distraction of attention as well as satiety resulted in disappearance of unit responses corresponding to correct task solution. At the same time the animal failed to perform the food procuring movement or correct change in the movement side after the delay period. Relations between rearrangements in unit activity and environmental and internal organism changes are discussed.

Animals↗
PubMedDate not supplied

[Differences in the effects of piracetam and fenazepam in emotional stress caused by the spatial reversal of a habit].

Emotional stress was caused in rats by changing the location of the gate in the shuttle chamber through which training had been accomplished in the previous experiments. The procedure led to disorder of the avoidance response (AR) and increase of intertrial responses (ITR). Phenazepam (0.1 mg/kg) prevented increase in the number of ITS. Piracetam (300 mg/kg) reduced the sharp growth of ISR but, in contrast to phenazepam, it provided a higher level of AR reproduction. The ISR were greater in piracetam than in phenazepam administration. The obtained results show that the suggested model allows the difference in the effects of piracetam and phenazepam to be disclosed.

Animals↗
PubMed1997

Effects of postnatal exposure to a PCB mixture in monkeys on nonspatial discrimination reversal and delayed alternation performance.

Behavioral impairment as a consequence of PCB exposure beginning in utero has been reported in both humans and animals. The present study assessed the behavioral consequences of postnatal exposure to PCBs. Male monkeys (Macaca fascicularis) were dosed from birth to 20 weeks of age with 7.5 micrograms/kg/day of a PCB mixture representative of the PCBs typically found in human breast milk (8 monkeys) or vehicle (5 monkeys). At 20 weeks of age, PCB levels in fat and blood of treated monkeys were 1.7-3.6 ppm and 2-3 ppb respectively. Beginning at three years of age, monkeys were tested on a series of nonspatial discrimination reversal problems followed by a spatial delayed alternation task. Treated monkeys exhibited decreased median response latencies and variable increases in mean response latencies across the three tasks of the nonspatial discrimination reversal. There were no group differences on accuracy of performance, although some treated individuals made more mistakes at the beginning of the experiment than did control monkeys. On the delayed alteration task, the PCB-exposed group displayed retarded acquisition of the task and increased errors at short delay values, which were tested at the beginning of the experiment. There was no increase in the total number of errors in treated monkeys at long delay values. Treated monkeys engaged in more perseverative responding than controls over the entire course of the experiment, in some instances even in the absence of an increase in overall error rate. These findings are interpreted as a learning/performance decrement rather than an effect on spatial memory per se. The results of this study suggest that PCB exposure which is limited to the early postnatal period and results in environmentally-relevant body burdens produces long-term behavioral impairment.

Adipose Tissue↗
PubMed1973

Pup retrieving as a reinforcer in nulliparous mice.

Six nulliparous female mice were trained to bar press with bar pressing reinforced by the opportunity to retrieve pups to the nest. Then, responses on one bar produced the opportunity to retrieve pups, while responses on a second bar produced sensory contact with non-retrievable pups, presented behind a screen door. All subjects emitted more responses on the bar yielding retrievable pups. When the bar-pup contingency was reversed, five subjects learned to press the opposite bar for retrievable pups. The sixth subject showed extinction of responding on the bar that had previously yielded retrievable pups, but failed to press the other bar. A major portion of the reinforcing value of pup presentation resulted from the opportunity to perform the behavior of pup retrieving. This finding supports theoretical formulations which state that the performance of species-typical consummatory behaviors should have reinforcing properties.

Animals↗
PubMed1984

An involvement of acetylcholine in object discrimination learning and memory in the marmoset.

Five marmosets (Callithrix jacchus) were tested, using a Wisconsin General Test Apparatus, on a series of junk object visual discrimination tasks, including new learning, 24-hr reversal and 24-hr retention. The effects of administering the cholinergic receptor blocking agent, scopolamine either just before or immediately after the new learning task, or just before the 24-hr reversal and retention tasks, were assessed. Results suggest that scopolamine impairs new learning and impairs the encoding of new information in long term memory. Some evidence of a mild retrieval deficit under scopolamine was also seen, while state-dependent effects were not apparent.

Acetylcholine↗
PubMed1986

Reversal and nonreversal shifts under amphetamine.

Rats were trained in a Y maze on a two-choice simultaneous brightness discrimination with light as S+ and dark as S- (position irrelevant). Half of the animals were then switched to reversal, where the reinforcement contingencies of the original training were reversed, and the other half were switched to nonreversal, in which they learned a simultaneous right-left discrimination. Nonreversal was acquired faster than reversal in saline injected animals. The administration of 1 mg/kg d-amphetamine did not affect the acquisition of the initial brightness discrimination and of nonreversal. In contrast, the drug facilitated dramatically reversal learning. The results indicate that amphetamine enhances the attention to, or the associability of, the discriminative stimuli, leading to rapid learning to these stimuli under changed contingencies of reinforcement.

Animals↗
PubMed1986

Comparative neuropsychology of cortical and subcortical dementia.

The terms "cortical" and "subcortical" dementia are controversial; however, the clinical distinction between them is real. For example, although Alzheimer's and Parkinson's disease (prototypical of cortical and subcortical dementia, respectively) share clinical features, they differ in the presence of aphasia, apraxia, and agnosia in Alzheimer's disease but not in Parkinson's dementia. We review our studies aimed at clarifying the mechanisms underlying the differences between these neurological disorders. Experimental paradigms adopted from animal models were used to study the functional anatomy and neuropsychological characteristics of Alzheimer's and Parkinson's disease. The tasks administered include delayed alternation (DA) and delayed response (DR), which are sensitive to frontal system damage, and tactile discrimination learning (TOL) and reversal (TRL) paradigms sensitive to parietal system damage. Alzheimer's patients were significantly impaired on all tasks whereas Parkinsonians with dementia were impaired only on DR and TRL. Consideration of neuroanatomical and neuropsychological mechanisms involved in DA, DR, TOL, and TRL appears to have sharpened the distinction between Alzheimer's and Parkinson's dementia. Dementia in Alzheimer's disease may involve dorsolateral frontal, orbitofrontal and parietal systems. In contrast, dementia in Parkinson's disease may involve prominent dorsolateral frontal system damage.

Dementia↗
PubMed1999

Presumed 'prefrontal cortex' lesions in pigeons: effects on visual discrimination performance.

The posterodorsolateral neostriatum (PDLNS) in pigeons may be an equivalent of the prefrontal cortex (PFC) in mammals. Here we report that lesions of this brain region in pigeons have a detrimental effect on various learned visual discriminations. Pigeons with lesions of the overlying area corticoidea dorsolateralis (CDL) served as controls. Both the postoperative re-learning to criterion of a preoperatively learned simultaneous double visual mirror pattern discrimination and the learning of a simple successive go, no-go discrimination were impaired by the PDLNS lesions. The PDLNS and CDL groups did not differ significantly in the postoperative learning of a reversal of the simultaneous discrimination. The results are discussed in relation to the presumed equivalence between the avian PDNLS and the mammalian PFC.

Animals↗
PubMed2004

The reverse hierarchy theory of visual perceptual learning.

Perceptual learning can be defined as practice-induced improvement in the ability to perform specific perceptual tasks. We previously proposed the Reverse Hierarchy Theory as a unifying concept that links behavioral findings of visual learning with physiological and anatomical data. Essentially, it asserts that learning is a top-down guided process, which begins at high-level areas of the visual system, and when these do not suffice, progresses backwards to the input levels, which have a better signal-to-noise ratio. This simple concept has proved powerful in explaining a broad range of findings, including seemingly contradicting data. We now extend this concept to describe the dynamics of skill acquisition and interpret recent behavioral and electrophysiological findings.

Cerebral Cortex↗
PubMed1997

Analyses of response patterns clarify lead effects in olfactory reversal and extradimensional shift tasks: assessment of inhibitory control, associative ability, and memory.

Rats exposed to lead (Pb) chronically from conception were tested on (a) an olfactory serial reversal task and (b) an extradimensional shift (EDS) task. Pb exposure did not impair learning of the original olfactory discrimination but did impair learning of the 5 reversals and the EDS task. In the reversals, Pb exposure tended to shorten the initial period of persistent responding to the previously correct cue, but significantly prolonged the postperseverative learning phase (both the "chance" and "greater-than-chance" components). These effects are similar to those produced by lesions of the amygdala, a structure implicated in the process by which stimuli acquire incentive value. This similarity, coupled with the pattern of findings, suggests that Pb-induced impairment of reversal learning is due to a deficiency in learning the new contingencies of the task (an associative deficit), not inflexibility or deficient inhibitory control. These findings also illustrate the importance of analyzing the types of errors committed, rather than focusing solely on learning rate.

Amygdala↗