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At least 1,621 records · Page 90Linked to original sources
PubMed2005

Intact visual discrimination of complex and feature-ambiguous stimuli in the absence of perirhinal cortex.

The perirhinal cortex is known to be important for memory, but there has recently been interest in the possibility that it might also be involved in visual perceptual functions. In four experiments, we assessed visual discrimination ability and visual discrimination learning in severely amnesic patients with large medial temporal lobe lesions that included complete lesions of perirhinal cortex. Experiment 1 tested complex visual object perception. Experiments 2a and 2b tested in two different ways the ability to discriminate between feature-ambiguous images, which was reported to be impaired in monkeys with perirhinal lesions. Experiment 3 involved images that were successfully discriminated in Experiment 2a and asked patients to learn across 20 trials which of the images had been designated as "correct." Patients performed as well as controls in Experiments 1, 2a, and 2b, but one of the patients had difficulty in Experiment 3 when the task required remembering from trial to trial which image was "correct." These findings indicate that perirhinal cortex is not needed for visual perception across a wide range of visual perceptual tasks.

Aged↗
PubMed1997

Functional changes of rat brain microsomal membrane surface after learning task depending on dietary fatty acids.

Biochemical characteristics of brain microsomal membranes were examined before and after the brightness-discrimination learning tasks in rats that were fed either safflower oil (alpha-linolenate-deficient) or perilla oil (alpha-linolenate-sufficient) diets. We detected small changes in the chain elongation system for polyunsaturated fatty acids in microsomes, whereas no significant difference was detected in the inositol trisphosphate-induced calcium release and ATP-induced calcium uptake profiles of microsomes between the two dietary groups. The calcium ion-induced aggregation rate of microsomes was determined in both groups. We found that the aggregation rate of microsomes in the safflower oil group was significantly greater than that in the perilla oil group. The difference in susceptibility of microsomal membrane phospholipids to phospholipase A2 between the groups was obvious, and the amount of released fatty acids by phospholipase A2 from the perilla oil group microsomes was nearly half of that from the safflower oil group microsomes after the learning task. Susceptibility of sialic acids on the brain microsomal membranes to exogenous sialidase was different only after the learning task in the safflower and perilla oil groups. These results suggest that the biochemical characteristics of membrane surfaces of brain microsomes are affected significantly by the learning task itself in a dietary oil-dependent manner.

Animals↗
PubMed1997

Categorization and perceptual learning: an analogue of the face inversion effect.

This paper reports two experiments that investigate the extent to which it is plausible to suppose that an associatively based mechanism for perceptual learning acts as the basis for the effects of inversion on identification, recognition, matching and discrimination of faces (and certain other stimuli rendered familiar by expertise, e.g. gundogs). In the first experiment, an inversion effect that is contingent both on familiarity with a category and on the category possessing prototypical structure is demonstrated using discrimination learning of chequerboard stimuli. The second experiment demonstrates that the inversion effect found in Experiment 1 can generalize to a recognition paradigm as well. These results are discussed within the framework provided by associative learning theory, and a parallel is drawn with models employing a norm-based coding in similarity space. The conclusion is that it would be remarkable if the inversion effects demonstrated with the abstract categories used in the experiments reported here were not implicated in the inversion effects found with other classes of stimuli, whilst conceding that the analogy is not complete, particularly in the case of faces.

Adolescent↗
PubMed1991

T-maze discrimination and reversal learning after unilateral temporal or frontal lobe lesions in man.

The interpretation of conditional discrimination and reversal learning as acquisition of declarative knowledge suggests that subjects with temporal lobe/hippocampal lesions are likely to be impaired on such tasks. Patients with unilateral left or right temporal lobectomy (and small hippocampal excisions) and patients with unilateral frontal lobe resections were compared with healthy controls on a discrimination reversal task, embedded in a computer game modelled on T-maze tasks traditionally used in animal experiments. The right temporal group showed a deficit in acquiring an initial conditional discrimination, and the frontal group tended to display a marginal impairment in discrimination reversal. These findings are compared with results from animal studies in terms of the mechanisms underlying reversal learning.

Adult↗
PubMed1999

Discrimination, reversal, and shift learning in Huntington's disease: mechanisms of impaired response selection.

In a series of three experiments, we investigated different aspects of response selection in early-stage clinically symptomatic Huntington's disease (HD) patients in the context of discrimination learning. A series of structurally related response selection tasks involving discrimination, reversal, and shift learning were employed. In Experiment 1, the mechanisms of our previously reported [37] finding of impaired extra-dimensional shift learning were explored. The results suggested that impaired shift learning in HD is a result of perseverative responding. In Experiment 2, performance on a concurrent-pair (CP) discrimination and reversal task was examined. HD patients showed no deficits in CP discrimination learning or reversal. In Experiment 3, the performance of HD patients on a probabilistic discrimination and reversal task was examined. HD patients were impaired in the learning of a probabilistic discrimination, and also its reversal. This reversal deficit was again the result of perseverative responding. In addition, there was a strong correlation between HD patients' activities of daily living scores and reversal errors. The result are consistent with current theories of the role of the basal ganglia in cognition, and suggest specific impairments in response selection mechanisms in HD, in particular, in overcoming selection biases based on prior reinforcement.

Adult↗
PubMed2003

Experimental evidence for spatial learning in cuttlefish (Sepia officinalis).

Laboratory mazes were used to study spatial-learning capabilities in cuttlefish (Sepia offcinalis), using escape for reinforcement. In preliminary observations, cuttlefish in an artificial pond moved actively around the environment and appeared to learn about features of their environment. In laboratory experiments, cuttlefish exited a simple alley maze more quickly with experience and retained the learned information. Similar improvement was not found in open-field mazes or T mazes, perhaps because of motor problems. Cuttlefish learned to exit a maze that required them to find openings in a vertical wall. The wall maze was modified to an arena, and simultaneous discrimination learning and reversal learning were demonstrated. These experiments indicate that cuttlefish improve performance over serial reversals of a simultaneous, visual-spatial discrimination problem.

Animals↗
PubMed2005

Response to novelty correlates with learning rate in a Go/No-go task in Göttingen minipigs.

Novelty-seeking and harm-avoidance personality traits influence Go/No-go (GNG) learning in humans. Animal studies have also indicated a link between response to novelty and spatial discrimination learning. In the present study, we test the hypothesis that learning rate in a GNG task correlates with the behavioral response of Göttingen minipigs to novelty. In a group of 12 minipigs of mixed genders, response to novelty was measured by numbers of contacts with a novel object, and the total duration of exploration of the novel object. These parameters were correlated to individual learning rate in a GNG task. The number of sessions to reach criterion in the GNG task correlated significantly with the number of contacts to a novel object (r = 0.70, p = 0.03), but not with the duration of object exploration (r = 0.29, p = 0.41). Thus, pigs with a low behavioral response to novelty learned the GNG task faster than did pigs with a strong behavioral response to novelty, indicated by the tendency to approach novel objects. We hypothesize that the critical factor in this relation is difference in emotional reactivity rather than difference in motivation for exploration. In conclusion, in addition to 'cognitive' ability, 'temperamental' factors are likely to influence learning in individual pigs.

Animals↗
PubMed1991

Behavioural method to detect marginal neurotoxic effects of ivermectin in DA/Orl rats.

Ivermectin (22, 23-dihydroavermectin B 1) in subtoxic doses was administered subcutaneously to young adult DA rats. Prior to treatment the rats had been trained in a visual discrimination learning programme until their response pattern was stable. The behavioural response data were recorded during continued discrimination testing following the Ivermectin injection and compared with those of a control group. The results showed that the Ivermectin injection reduced the total number of lever presses and reinforcement collections. Further the treatment caused an increase in the total number of erroneous responses.

Animals↗
PubMed1982

Specific and non-specific effects of neuro-excitatory amino acids on learning and other behaviours in the chicken.

Intracranial administration of glutamate to the chicken in the first week of life subsequently retards visual discrimination learning. After this susceptible period in the first week, the brain can more effectively metabolize or extrude a loading dose of glutamate. The potent glutamate and aspartate agonists, kainic acid and N-methylaspartate, also retard learning, but alpha-methylaspartate, which is electrophysiologically inactive, does not. Kainic acid also shares glutamate's requirement for interaction with patterned visual input if it is to retard visual learning. Since the amino acid putative neurotransmitters, gamma-aminobutyric acid, taurine and aspartate, also retard visual learning, this effect on behaviour is non-specific. In contrast, glutamate administered to the left hemisphere has a specific effect in elevating attack and copulation, mimicked only by kainic acid and very high doses of N-methylaspartate, but not by the other amino acid putative neurotransmitters. This action of glutamate also differs from its retardation of learning in that is has no requirement for interaction with patterned visual input.

Aggression↗
PubMed1996

The pigeon's recognition of drawings of depth-rotated stimuli.

Four experiments used a four-choice discrimination learning paradigm to explore the pigeon's recognition of line drawings of four objects (an airplane, a chair, a desk lamp, and a flashlight) that were rotated in depth. The pigeons reliably generalized discriminative responding to pictorial stimuli over all untrained depth rotations, despite the bird's having been trained at only a single depth orientation. These generalization gradients closely resembled those found in prior research that used other stimulus dimensions. Increasing the number of different vantage points in the training set from one to three broadened the range of generalized testing performance, with wider spacing of the training orientations more effectively broadening generalized responding. Template and geon theories of visual recognition are applied to these empirical results.

Animals↗
PubMed1981

A new approach to the role of noradrenaline in learning: problem-solving in the marmoset after alpha-noradrenergic receptor blockade.

Nine marmosets (Callithrix jacchus) were tested on a variety of visual discrimination learning tasks in a Wisconsin General Test Apparatus with or without alpha-noradrenergic receptor blockade achieved by the administration of aceperone. After aceperone, animals were found to be severely and consistently impaired at learning the first task of each test session and to be impaired on new and repeated reversal learning. They were, however, unimpaired on learning another similar task in each test session and on performance of a well-learnt task. Results were interpreted as evidence for defective association formation which can be compensated for by suitable priming or practice.

Adrenergic alpha-Antagonists↗
PubMed1986

Can rats learn to associate a flavour with the delayed delivery of food?

Associations between a specific flavour and access to food were studied using a discrimination procedure devised by Holman (1975). This involved giving rats one flavour (e.g. cinnamon) of saccharin solution on some days, and following this by delivery of food, and a second flavour (e.g. wintergreen) on other days which was never followed by food. Experiment 1 used glucose delivered after a 30-min delay and a slight increase in preference for the paired flavour was detected. Using a 20-min delay Experiment 2 varied the kind of food used; some evidence for discrimination learning was again found in the glucose group, but there was no evidence that rats could associate a flavour with starch solution or solid chow over this delay. To check that the general procedure was a sensitive one, in Experiment 3 one flavour was added to glucose i.e. without delay, and this produced large shifts in a subsequent preference test. Overall the results threw doubt on claims that rats as readily form flavour-calorie associations over delays as they do flavour-toxicosis associations.

Animals↗
PubMed1981

The effect of a unilateral ablation of the occipital lobe on pattern discrimination in the rabbit.

Binocular brightness and striated pattern discrimination were studied in Dutch-belted rabbits. A comparison was made between normal animals and animals in which a unilateral lesion of the occipital lobe had been made three months after birth. No difference between the two groups was found in brightness discrimination learning. However, normal animals were found to do better both in acquisition and accuracy of striated pattern discrimination.

Animals↗
PubMed1976

Effects of para-chlorophenylalanine and tryptophan on learning of a brightness discrimination in rats.

Both the learning of brightness discrimination, discrimination reversal and a simple oddity problem, and the pain-sensitivity to electric shock were studied in rats treated with 100 mg/kg of D, L-parachlorophenylalanine (PCPA), 100 mg/kg of D, L-tryptophan (TP) or 2.0 ml/kg of control solution (CS). At the end of the last behavioral session all animals were killed and the levels and rate of 5-hydroxytryptamine (5-HT) synthesis were measured. PCPA treatments produce rats which are more effective in coping with a problem; these animals were similar in that both the levels and turnover rate of brain 5-HT and the pain-sensitivity were lower. Results are tentatively explained suggesting that these differences in learning ability could be a result of the drug's action in pain-sensitivity. The possibility that 5-HT might be responsible for these differences is discussed.

Animals↗
PubMed1989

Learning about rules but not about reward is impaired following lesions of the cholinergic projection to the hippocampus.

Common marmosets with bilateral ibotenic acid-induced destruction of the neurones of the vertical limb of the diagonal band of Broca, which provide the major cholinergic input to the hippocampal formation, were impaired on the acquisition but not on the retention of a repeated-trial visuospatial discrimination learning task. They were also impaired on serial spatial reversal learning (but not on serial object reversal learning), on acquisition of a trial-independent successive concurrent discrimination using novel objects (but not on acquisition of a comparable discrimination in which two familiar objects had predictable reward value) and were unable to acquire a difficult conditional object discrimination. It is argued that the role of the hippocampus is in the acquisition but not the retention of ruled-based behaviour (which includes spatial responding) in contrast to the acquisition of discriminations based on stimulus-reward association formation.

Animals↗
PubMed2001

Effects of the uterine environment and neocortical ectopias upon behavior of BXSB-Yaa+ mice.

Between 40-60% of BXSB-Yaa+mice have neocortical ectopias, a genetically based brain anomaly. The presence of ectopias is known to affect several cognitive measures. A second way to affect cognition is by transferring embryos into foreign uteri. These variables were jointly investigated in three experiments. BXSB-Yaa+mouse embryos were transferred into same-strain uteri, or into uteri of hybrid mice. At birth, pups were cross-fostered to hybrid mothers or were reared by their birth mothers. When adult, the mice were given a series of behavioral tests with primary emphasis upon cognitive competence. Across all three studies, mice transferred into hybrid uteri were superior in the Morris maze and the Lashley III maze, and performed more effectively in shuttlebox avoidance learning. They were less effective in the simple water escape task, and the uterus groups did not differ in discrimination learning. Thus, development within a foreign uterus enhanced spatial learning and fear-based conditioning. Ectopic mice were superior to non-ectopics in learning the Morris maze, a finding consistent with prior research using the congenic BXSB-Yaa strain. There were Uterus x Ectopia interactions on a few measures, indicating that, under certain condition, whether the presence of ectopias is beneficial or detrimental is contingent upon the uterine environment within which the organism develops.

Animals↗
PubMed2004

Dimensional approaches to experimental psychopathology of schizophrenia: shift learning and report of psychotic-like experiences in college students.

Adopting a dimensional approach to experimental psychopathology, and taking into account inconsistencies in the previous literature, we examined whether reports of psychotic-like experiences in undergraduate students were associated with shift-learning deficits, akin to those seen in schizophrenia. The participants (N=72) were tested on a new compound stimulus discrimination task before and after a target shift, and were administered a multi-dimensional schizotypy inventory (O-LIFE). Performance impairment following a target shift was associated with the negative (introvertive anhedonia) and the impulsive (impulsive non-conformity) dimension of schizotypy, but not with the positive (unusual experiences), nor the disorganised (cognitive disorganisation) dimension. None of the schizotypy measures were associated with performance on discrimination learning before the target shift. The obtained results are in line with past evidence that shift learning is associated with the severity of the negative symptomatology of schizophrenia. The possibility that psychotic-like features may contribute differentially to performance deficits across successive stages of learning is considered.

Adolescent↗
PubMed1975

Successive spatial discrimination reversals in the prairie dog.

Six prairie dogs (Cynomys ludovicianus) were given reversal training on a spatial discrimination reversal task in a Wisconsin General Test Apparatus (WGTA). As with many other species, more errors occurred on the first reversal problem than during acquisition of the original discrimination. However, performance improved over training until each S eventually reversed after a single nonreinforced error. Initial findings indicate that prairie dogs perform at high levels in discrimination learning experiments and could be valuable subjects for psychological research.

Animals↗