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Results for “Reversal Learning”

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At least 811 records · Page 45Linked to original sources
PubMed1992

A specific form of cognitive rigidity following excitotoxic lesions of the basal forebrain in marmosets.

The effects of N-methyl-D-aspartate-induced lesions of the basal forebrain were studied on performance of a series of visual discrimination tests that examined a range of cognitive functions in the marmoset. These included the ability to attend to the various dimensional properties of stimuli and to use just one of these properties in order to solve a discrimination (intra-dimensional shift); to switch attention from one dimension to another (extra-dimensional shift); to learn the reinforcement value of specific exemplars within a dimension (new learning); and to relearn their reinforcement value following reversal of the reward contingencies (serial reversals). Lesions of the basal forebrain did not impair the ability either to attend selectively to the dimensional properties of the stimuli or to switch attention from one dimension to the other. However, the lesion did affect various aspects of associative learning including a transient impairment of new learning and a marked disruption of serial reversal learning. The reversal deficit could be characterised as a tendency to perseverate on the previously correct stimulus and as a failure to to show the formation of a reversal learning set. In addition, the lesion prevented disruption of performance of a well-learned discrimination when novel exemplars from the irrelevant dimension were introduced (probe test). It is suggested that the functional effects of the basal forebrain lesion reflect impaired learning of stimulus-reward associations and behavioural rigidity. The finding, however, that there was no effect of the lesion on attentional set-shifting suggests that any loss of inhibitory control was specific to the level of stimulus-response or stimulus-reward associations, inhibitory control at the level of attentional selection remaining intact. The similarity of the effects of damage to the basal forebrain to those seen following damage to the orbitofrontal cortex and the amygdala are discussed in the context of the close anatomical and functional relationships that exist among these three structures.

Animals↗
PubMed2006

Cognitive inflexibility after prefrontal serotonin depletion is behaviorally and neurochemically specific.

We have previously demonstrated that prefrontal serotonin depletion impairs orbitofrontal cortex (OFC)-mediated serial discrimination reversal (SDR) learning but not lateral prefrontal cortex (PFC)-mediated attentional set shifting. To address the neurochemical specificity of this reversal deficit, Experiment 1 compared the effects of selective serotonin and selective dopamine depletions of the OFC on performance of the SDR task. Whereas serotonin depletions markedly impaired performance, OFC dopamine depletions were without effect. The behavioral specificity of this reversal impairment was investigated in Experiment 2 by examining the effect of OFC serotonin depletion on performance of a modified SDR task designed to distinguish between 3 possible causes of the impairment. The results showed that the reversal deficit induced by prefrontal serotonin depletion was not due to a failure to approach a previously unrewarded stimulus (enhanced learned avoidance) or reduced proactive interference. Instead, it was due specifically to a failure to inhibit responding to the previously rewarded stimulus. The neurochemical and behavioral specificity of this particular form of cognitive inflexibility is of particular relevance to our understanding of the aetiology and treatment of inflexible behavior apparent in many neuropsychiatric and neurodegenerative disorders involving the PFC.

5,7-Dihydroxytryptamine↗
PubMed1972

The behavior of chronic cats with lesions in the frontal association cortex.

Cats with lesions in the proreal and anterior sigmoid gyri and substantial but subtotal degeneration in the mediodorsal thalamic nucleus were studied for 6 years post-operatively. The control group consisted of normal cats matched for age and previous experience. The results reported here and in Warren's previous progress report indicate that frontal cortical lesions result in several behavioral changes in cats which are like those seen in rhesus monkeys after frontal ablations: impairments in discrimination reversal, double alternation and active avoidance learning, retardation in the rate of habituation to novel neutral stimuli, and a decrease in aggression in competitive social situations. Cats with larger frontal lesions made more errors in reversal learning than cats with smaller lesions. Frontal cats, unlike frontal rhesus monkeys, are not hyperactive post-operatively and retain some capacity for learning delayed response in the WGTA. It is impossible at present to tell whether these discrepancies reflect species differences in the organization of the frontal lobe system or whether the frontal cortex spared in this series of cats is sufficient to mediate delayed response and to prevent the occurrence of hyperactivity.

Aggression↗
PubMedDate not supplied

Image rotation and reversal--major obstacles in learning intracorporeal suturing and knot-tying.

BACKGROUND AND OBJECTIVES: A major stumbling block to teaching and learning the finer skills of laparoscopy is related to the "optical illusions" the video camera plays on the surgeon's eyes. Until now, the belief was that lack of coordination was the result of depth perception deficiencies resulting from the two dimensional plane of the video monitor. In reality, this is a minor problem that is easily surmounted with practice. A closer analysis of how organ orientation at the operative site compares to the video camera's fields of focus reveals the real problem: the major optical difference between laparotomy and laparoscopy involves rotation of the images received by the brain. CONCLUSIONS: There are four major operating positions in laparoscopy: camera position, right camera position, left camera position and opposite camera position. The object in front of the camera has two components; the first, a reality image, which results from light reflected off the object as it exists in time and space. The second, a visual image, which represents the actual light entering our eyes. At right camera position the visual image is a 90 degrees counter-clockwise rotation of the reality image. At the left camera position the visual image is a 90 degrees clockwise rotation of the reality image. At opposite camera position, a 180 degrees rotation and complete reversal of the reality image occurs. It is only at camera position that the visual image is equal to the reality image, and we approach a scenario similar to that found in laparotomy. Every other position will be unlike what we were accustomed to in open surgery.

Clinical Competence↗
PubMed1980

The first year after treatment: factors affecting time course of reversibility of memory and learning deficits in alcoholism.

Ninety-two alcoholics admitted to the Tayside Area Alcoholism Unit in East Scotland were examined on four tests of memory and learning two weeks after cessation of drinking. Sixty-two were re-examined at four weeks, forty-one at eight weeks, thirty-five at six months and thirty-two at one year after initial abstinence, although some resumed drinking. There was a significant improvement in testing results over the year following treatment, greatest in the period from four to twenty-six weeks. Improvement was most marked in the patients who remained abstinent or almost abstinent and in those not malnourished at admission.

Adult↗
PubMed1981

Perseverative behaviour after amphetamine; dissociation of response tendency from reward association.

Low doses of amphetamine were found to alter the ability of marmosets to take account of changes in reward values of object stimuli in a visual discrimination task. Under amphetamine, animals changed their motor responses and stimulus choice in order to preserve the acquired reward value or meaning of certain stimuli. These results suggest that the perseverative effect of amphetamine on behaviour is due to impaired cognitive flexibility rather than to an enhancement of motor habit.

Animals↗
PubMed1985

Deficits in non-spatial conditional associative learning after periarcuate lesions in the monkey.

Monkeys with lesions of the periarcuate region of the frontal cortex were severely impaired in learning a nonspatial conditional associative task. In this task, either one of two non-spatial responses (open the lit or the unlit box) was correct if emitted in the presence of the appropriate stimulus. In contrast, the periarcuate monkeys were able to learn, at a normal rate, the control tasks in which only one of the two responses was correct (e.g., go to the lit box), the animal's task being to emit this response when the cue to do so was given. These findings support the hypothesis that the periarcuate cortex is critically involved in conditional associative learning.

Animals↗
PubMed1996

Perception, learning and identification studied with reversible suppression of cortical visual areas in monkeys.

We use cold to reversibly suppress cortical areas involved in visual perception, learning and retrieval and we found a localization of functions essential for performance of delayed match-to-sample (DMS) in anterior ventral temporal cortex, we call ventral TE (TEv). We also found a visual input for this area that is separate from the one going to the heart of inferotemporal cortex and suppressing this input also impairs performance of DMS. Suppressing the dorsal half of TE (TEd) disrupts retrieval of some, but not all complex images, and different images are disrupted in different animals. This variability within and between animals is extreme, with perfect performance on some complex images and below chance on others. We suggested that TEd represents some, but not all elements of the images. In attempting to discover what those elements might be, we found that TEd suppression disrupts the perception of small figures, but not the larger figures that they compose. We also found that it impaired the discrimination and matching of colors, without impairing the ability to detect and differentiate hues. We proposed that TEd represents the details and colors of things, but not global figures. Also, complex objects do not have a representation in one area, rather its representation involves the entire visual system, including TE with different elements of the image represented in different parts.

Animals↗
PubMed1997

Reversion to a previously learned foreign accent after stroke.

Foreign accent syndrome occurs rarely after stroke. Most patients with this syndrome develop an aphasia characterized by a new accent. This report presents a 48-year-old man who sustained a left parietal hemorrhagic stroke resulting in right hemiparesis and the inability to speak. As spontaneous speech emerged several weeks later, he was noted to have a Broca's aphasia and a Dutch accent. Analysis of his speech demonstrated final consonant deletion, substitution of "d" for "th" sounds, vowel distortions, additional "uh" syllables added at the end of words, and errors in voicing. This speech pattern has persisted for more than 5 years after the stroke. Elicitation of additional history found that the patient was born in Holland and lived there until the age of 5 years, when he moved to the United States with his family. Before his stroke, he had no foreign accent. This report illustrates the importance of considering foreign accent syndrome during aphasia recovery and suggests several pathogenetic mechanisms that may contribute to the development of this syndrome.

Brain↗
PubMed2003

The corticotropin-releasing factor receptor 1 antagonist CP-154,526 reverses stress-induced learning deficits in mice.

The neuropeptide corticotropin-releasing factor (CRF) coordinates the endocrine responses to stress as a major physiological regulator of the hypothalamic-pituitary-adrenal axis. We assessed the effect of the non-peptidergic CRF receptor 1 antagonist CP-154,526 on stress-induced changes in context-dependent fear conditioning and hippocampal synaptic plasticity. The learning impairment of mice trained immediately after 1 h immobilization could be overcome by preinjection of CP-154,526 before exposure to immobilization. Exposure to acute stress reduced the amount of autophosphorylated Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) in the hippocampal CA1 area. When animals were pretreated with CP-154,526 before immobilization, the amount of hippocampal autophosphorylated CaMKII was elevated. Electrophysiological studies in the hippocampal CA1 region of stressed animals revealed no significant effects of the CP-154,526 pretreatment on long-term potentiation but a significant elevation of paired-pulse facilitation (PPF) was observed. The CP-154,526-induced enhancements in fear conditioning and PPF could be prevented by the selective CaMKII inhibitor KN-62. Our results demonstrated that learning impairment after acute stress was antagonized by CP-154,526 pretreatment.

Animals↗