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Results for “Reversal Learning”

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At least 1,621 records · Page 90Linked to original sources
PubMed2000

Reversible inactivation of the hippocampal mossy fiber synapses in mice impairs spatial learning, but neither consolidation nor memory retrieval, in the Morris navigation task.

The role played by hippocampal mossy fibers in the learning and memory processes implemented in the Morris swimming navigation task has been studied in C57BL/6 mice by selective and reversible inactivation of mossy fiber synaptic fields by diethyldithiocarbamate. The functional integrity of the mossy fibers proved essential for the storage of the spatial representation on the modifiable synapses of the recurrent collaterals of the CA3 pyramidal cells, whereas it is not necessary for the consolidation and recall of spatial memories. The results suggest that mossy fibers are preferentially involved in new learning. They are consistent with the hypothesis that the hippocampal CA3 region might act as an autoassociation memory.

Animals↗
PubMed1980

Second-order appetitive conditioning in goldfish.

Second-order appetitive conditioning was studied in a series of experiments on goldfish. The first-order conditioned stimuli were white lines of different orientations projected on a target, the second-order conditioned stimuli were diffuse colors projected on the target, the unconditioned stimulus was liquid food delivered through a nipple at the center of the target, and the measured response was target striking. In the first experiment, sustained second-order conditioning was demonstrated. Evidence of colon-line association then was sought without success in two further experiments--a sensory preconditioning experiment in which second-order pairings preceded the first-order pairings, and a first-order revaluation experiment in which responses to second-order stimuli were measured after reversal training with positive and negative first-order stimuli. The stimulus-response reinforcement principle affords the best interpretation of the second-order conditioning demonstrated here: Responding to a second-order stimulus is strengthened by a contiguous first-order stimulus that acquires reinforcing properties on first-order trials.

Animals↗
PubMed1978

The effects of methylphenidate on repeated acquisition of serial discrimination reversals.

Rats were trained to bar-press for sucrose solution in the presence of one of two stimulus conditions. On each daily training session, the stimulus during which bar-pressing was reinforced was reversed. The subjects were trained in this Serial Discrimination Reversal procedure until successive acquisitions of the discrimination had stabilized. Drug treatments consisting of saline or 0.25, 1.0, 2.0, 4.0, 6.0 or 8.0 mg/kg of methylphenidate were then administered 20 min prior to the daily training sessions. Acquisition of the discrimination was enhanced by low doses of methylphenidate (1,2, and 4 mg/kg) and attentuated by higher doses (6 and 8 mg/kg).

Animals↗
PubMed1971

Transfer of stimulus control: measuring the moment of transfer.

Three severely retarded boys acquired simple form discriminations errorlessly. Each was first taught to press a red key versus a simultaneously present white key. After this discrimination had been established, black figures were superimposed on the red and white keys. Each correct response affected the next trial by delaying the onset of the red stimulus an additional 0.5 sec. Transfer of stimulus control to the figures was indicated when the subjects responded correctly before the onset of the red stimulus. A series of errorless discrimination reversals was accomplished with this technique, during which the number of trials to transfer systematically decreased with successive reversals.

Adolescent↗
PubMed2004

Two-way interactions between music and language: evidence from priming recognition of tune and lyrics in familiar songs.

A priming technique was employed to study the relations between melody and lyrics in song memory. The procedure involved the auditory presentation of a prime and a target taken from the same song, or from unrelated but equally familiar songs. To promote access to memory representations of songs, we varied the format of primes and targets, which were either spoken or sung, using the syllable /1a/. In each of the four experiments, a prime taken from the same song as the target facilitated target recognition, independently of the format in which it occurred. The facilitation effects were also found in conditions close to masked priming because prime recognizability was very low, as assessed in Experiment 1 by d' measures. Above all, backward priming effects were observed in Experiments 2, 3, and 4, where song order was reversed in the prime-target sequence, suggesting that words and tones of songs are not connected by strict temporal contingencies. Rather, the results indicate that, in song memory, text and tune are related by tight connections that are bidirectional and automatically activated by relatively abstract information. Rhythmic similarity between linguistic stress pattern and musical meter might account for these priming effects.

Adult↗
PubMedDate not supplied

Testing strategies in behavioral teratology: II. Discrimination learning.

Male and female Wistar rats exposed to methylmercury chloride prenatally via drinking water (1.5 and 5.0 mg/l) were tested in a microcomputer-directed learning task (visual discrimination reversal) at the age of two months. Differences were observed between control and high dose group for several parameters, the most obvious being an increase in passiveness and in response latency, as well as a decrease in intertrial interval response rates in the methylmercury group. No effects were seen in the low dose group. Performances of male and female animals were quite similar. However, females showed longer response latencies and passiveness scores were somewhat higher than in males.

Amphetamine↗
PubMed1989

Wulst lesions in pigeons disrupt go/no-go reversal.

Pigeons with lesions of either the Wulst or ectostriatum were compared to controls on reversal of a go/no-go pattern discrimination. The Wulst-lesioned animals were slower to acquire the response to the new S+ but were not different from the other groups on extinction of response to the old S+. The ectostriatum-lesioned group was not different from controls. The results extend the range of situations in which Wulst-lesioned pigeons have been found to show a reversal deficit and are consistent with the notion that Wulst lesions may disrupt learning.

Animals↗
PubMed1990

Effects of physostigmine on operant serial discrimination/reversal learning in rats.

Two experiments examined the effects of physostigmine on acquisition and performance of operant serial reversals by rats. In Experiment 1, four groups of rats (n = 6/group) were injected with either vehicle or 0.03 mg/kg physostigmine five minutes prior to each session, or vehicle or 0.5 mg/kg physostigmine immediately after each session of a three-stimulus (bright, dim or flashing light) repeated discrimination/reversal procedure. Rats treated with physostigmine pre- or postsession learned significantly more reversals over 50 sessions than animals injected with vehicle. Experiment 2 used only two discriminative stimuli, a light and a 2,500 Hz tone. Following establishment of a stable daily reversal baseline, postsession injections of physostigmine significantly increased the number of trials to criterion on the next session compared to each subject's control baseline. Results are attributed to enhanced between-session transfer of previously learned discriminated instrumental responses by physostigmine-treated animals.

Analysis of Variance↗
PubMed1993

Role of the amygdala complex in early olfactory associative learning.

Although olfactory associative conditioning in newborn rats produces marked structural and functional changes in the olfactory bulb, recent evidence suggests that extrabulbar circuits must be involved in storing these early memories. The present experiments examined the role of the amygdala complex on early olfactory learning. Bilateral amygdala lesions or sham lesions were performed on Postnatal Day (PN) 5. On PN6, pups were trained in a standard classical conditioning paradigm associating odor with tactile stimulation. Behavioral testing on PN7 revealed that amygdala lesions blocked odor preferences but had no effect on conditioned behavioral activation. Similar sized neocortical lesions did not impair odor preferences. Importantly, amygdala lesion effects on learned odor preferences could be reversed by extensive overtraining. These results suggest that the amygdala complex plays a critical role in modulating associative learning as early as the first postnatal week in the rat.

Aging↗
PubMed1986

Aluminum ingestion and behavior in the Long-Evans rat.

A variety of behaviors was measured in adult Long-Evans male rats fed ground rat chow containing either no added aluminum, low aluminum (1500 mg/kg), moderate aluminum (2500 mg/kg), or high aluminum (3500 mg/kg). There were no effects of aluminum on either body weight or mouse killing. There was an inverse relationship between brain aluminum and open-field activity. Elevated brain aluminum was correlated with relatively poor performance on a single-trial passive-avoidance task and on a visual discrimination with reversal task.

Aggression↗
PubMed1998

[Experiences with "reversed tip and snip" phacoemulsification].

UNLABELLED: The endothelial cell count after phacoemulsification serves as a sensitive indicator for the level of corneal traumatization caused by different phacoemulsification techniques concerning the used phacotime and phacoenergy/s. PATIENTS: In a prospective and randomized study, the "reversed tip and snip" technique and the "divide and conquer" technique were performed in groups of 30 patients each. The corneal endothelial cell count was measured preoperatively as well as 4 weeks and 3 months postoperatively. In a second study the phacotime and phacoenergy used/second and the endothelial cell loss were compared between patients 1-30 and 31-60 who were operated on with the "reversed tip and snip" technique, demonstrating the learning curve of this technique. RESULTS: The endothelial cell count showed significant (P < 0.001) reduction by about 10% after the "reversed tip and snip" technique and by about 15% after the "divide and conquer" technique. The latter produced significantly greater cell loss. The phacotime (mean: 22-17) and phacoenergy/s (mean: 23-16) were reduced significantly (P < 0.05) when patients 1-30 were compared with 31-60. CONCLUSION: The "reversed tip and snip" phacoemulsification technique produces less endothelial cell loss than the "divide and conquer" technique. There is a short learning curve by using the "reversed tip and snip" technique.

Aged↗