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PubMed1992

Effects of dihydroergotoxine on central cholinergic neuronal systems and discrimination learning test in aged rats.

We evaluated changes in the cholinergic neuronal system and learning ability with aging. Choline acetyltransferase (ChAT) activity, a presynaptic index of the cholinergic system, was decreased in the cerebral cortex, hippocampus, striatum, and hypothalamus in the brain of aged rats compared with young adults. Muscarinic cholinergic binding sites (receptors, MCR), a postsynaptic index of the cholinergic system, were markedly decreased in all areas of the brain. However, intraperitoneal injection of 1 mg/kg of dihydroergotoxine (DHET) for 14 days normalized both ChAT and MCR in the cerebral cortex and hippocampus. In the striatum, ChAT was normalized, but MCR did not recover. Aged rats showed marked learning impairment in a 30-day operant type brightness discrimination learning test. Daily DHET administration restored the discrimination ability in the aged rats to nearly the young adult level. DHET had no effects on central cholinergic indices or learning test results in young adult rats. These findings suggest that learning is impaired in aged rats due to impairment in the central cholinergic neuronal system, and that DHET normalizes the decreased function in this system, restoring the learning ability.

Aging↗
PubMed1989

Effect of piracetam, a nootropic agent, on discrimination learning deficits induced by parental undernutrition and environmental impoverishment in young rats.

The study was conducted on 64 Charles Foster albino rats which were equally distributed into 8 even-matched groups, following a 2 x 2 x 2 factorial design by varying three independent factors at two levels: nutrition--normal and undernutrition, environmental--enrichment and impoverishment, and drug treatment--vehicle and piracetam (100 mg/kg, ip). Prenatal nutrition was induced by restricting the mother's food intake. The environmental enrichment/impoverishment and the vehicle/drug treatments were given during the postweaning period of the rat pups. The animals were subjected to original and subsequent reversal brightness discrimination learning tests in a single unit T-maze at 8-9 weeks of age. The results indicate that undernutrition and environmental impoverishment significantly attenuated the original discrimination as well as the reversal discrimination learning. Piracetam treatment improved the learning performance of normally reared rats and also attenuated the original and reversal learning deficits induced by prenatal undernutrition and postnatal impoverishment. The results indicate that piracetam may be useful in memory deficits induced by malnutrition.

Analysis of Variance↗
PubMed1985

Genetic differences in avoidance learning by Rattus norvegicus: escape/avoidance responding, sensitivity to electric shock, discrimination learning, and open-field behavior.

The behaviors of rats selectively bred for either good or poor shuttle box avoidance learning were studied. The results of Experiment 1 indicated that the phenotypic difference in avoidance learning is not associated with differences in speed of escape or avoidance responding. Differences between the lines in frequency of intertrial responses (ITRs), which appear during training but not during pretest, suggest that ITRs in animals of the low-avoidance (SLA) line are more suppressed by electric shock than in animals of the high-avoidance (SHA) line. This result suggests that SLA animals may be more emotionally responsive than SHA animals. Experiment 2 demonstrated that the animals of the two lines do not differ in absolute sensitivity to electric shock, and Experiment 3 showed that the poor performance of the SLA line is not due to an inability to learn. Experiment 3 also provided evidence which suggests that the poor avoidance learning by SLA animals is due to their emotional reactivity. Observations of open-field behavior in Experiment 4 are consistent with this hypothesis. The major consistent correlate of the phenotypic difference in avoidance learning is greater emotionality or emotional reactivity in SLA than in SHA animals.

Animals↗
PubMed1988

Delta-9-tetrahydrocannabinol impairs visual recognition memory but not discrimination learning in rhesus monkeys.

The effects of orally administered delta-9-tetrahydrocannabinol (THC) were evaluated on two different learning abilities in monkeys. Visual recognition memory, known to depend on limbic system integrity, was tested by means of delayed nonmatching-to-sample and found to be significantly impaired by acute administration of 2 and 4 mg/kg THC given 1 or 2 h prior to testing. Performance was significantly impaired throughout a 21-day period of repeated administration of 4 mg/kg THC and also during a 3-5 day period that began 7-10 days after the last dose of THC. By contrast, 24-h concurrent discrimination learning, a task that monkeys with limbic lesions can perform normally, was not impaired by THC, even following doses as high as 16 mg/kg. These results suggest that THC interferes with recognition memory more than discrimination learning, possibly reflecting a selective action of THC on limbic mechanisms.

Administration, Oral↗
PubMed1991

Hippocampus and the blood supply to TE: parahippocampal pial section impairs visual discrimination learning in monkeys.

In the base of each temporal lobe in 4 monkeys (Macaca fascicularis) we sectioned the pia mater in an antero-posterior line along the most medial part of the inferior temporal visual association cortex (area TE), lateral to the parahippocampal cortex. This pial section interrupts the blood flow in branches of the posterior cerebral artery which cross the parahippocampal gyrus en route to area TE. Histologically, the brains of 2 of these animals did not show any abnormalities in cresyl violet stained material, apart from the small cortical damage along the line of the pial section itself. Of the remaining two animals, one had a small unilateral infarct in TE and one had bilateral infarcts in TE. All of these animals were impaired in visual discrimination learning, and the severity of impairment was correlated only imperfectly with the severity of infarction. These results show that pial section along the medial boundary of area TE can affect visual discrimination learning without producing large infarcts. Further, since aspiration lesions of the hippocampal formation require the pia mater to be sectioned in a similar way to that reported here, the effects of such aspiration lesions on visual learning and memory may be mediated in part by effects on TE.

Animals↗
PubMed1985

Control of children's observing responses by information feedback during visual discrimination learning.

Four experiments examined the control of observing responses by information feedback during visual discrimination learning. Second-grade children participated in Experiment 1; kindergarten, second-, and fifth-grade children were subjects in Experiments 2 and 3, and grade 5 and adult subjects were tested in Experiment 4. In order to view the stimuli, subjects in Experiments 1, 2, and 3 activated lights in viewing boxes; in Experiment 4, stimulus fixations were measured using a corneal reflection technique. Fifth graders and adults observed the discriminative stimuli for longer times on trials following negative feedback than on trials following positive feedback; in contrast, kindergartener's observing was not affected by type of feedback. Second graders showed smaller and less reliable reactions to type of feedback than did older subjects. These results support the view that visual observing is controlled by cognitive processes associated with hypothesis testing.

Child↗
PubMed1983

Luck and learning: feedback contingencies and initial success in verbal discrimination learning.

Ninety undergraduate volunteers learned a 12-pair, low frequency, verbal discrimination list. The independent variables were feedback (positive only, negative only, or both) and initial success (17%, 50%, or 83% correct on trial one). With the total errors on nine trials as the dependent variable, the main effect of feedback was found to be not significant. The main effect of initial success was significant. Subjects who started at 50% correct had the most difficulty learning the list and subjects in the 83% correct condition learned quickest. The predicted interaction between feedback and initial success was not significant, even though the means for the three types of feedback at the 17% correct starting level reflect the expected differences. The results are interpreted as supporting the rule-use component of frequency theory. The relationship between initial success and subsequent performance appears to be curvilinear, rather than linear, as many theorists have assumed.

Discrimination Learning↗
PubMed1990

[Investigation of cortical slow potentials during the delayed discrimination learning in monkeys].

Averaged slow potentials (SPs) were recorded at different training stages of delayed discrimination learning in two monkeys. The details of the task sequence was described in our previous work. It was found that at the early stages of the training the amplitude of SPs was very small, and it increased gradually with the increase of percentage of correct responses. The SPs recorded from the prefrontal cortex had the largest amplitude and there was no SPs recorded from the rear portion of the cortex. SPs recorded from the symmetrical sites of the two hemispheres showed no significant differences in amplitude and duration. Moreover, the SPs did not show significant differences in amplitude and distribution between two test models (R Model and B Model). The results obtained from the extinction experiments showed that after extinction of the behavioral responses the SPs disappeared. The results showed that the SPs recorded were learning-dependent and represented the association of events. As the SPs appeared in the delay period and were prefrontal-dominant, it was suggested that the prefrontal cortex might play an important role in short-term memory process.

Action Potentials↗
PubMed1990

Configural associations in discrimination learning.

In 4 experiments, Sprague-Dawley rats and homing pigeons received training with an A+ AB0 BC+ discrimination, in which food (+) accompanied trials with A and BC. Food was not presented (0) on trials with the compound AB. Subsequent test trials revealed that responding during C by itself, or the compound ABC, was slower than during either A or BC. Responding during the ABC compound was also found to be slower after training with the A+ AB0 BC+ than an A0 AB+ BC+ discrimination. We argue that these findings demonstrate the importance of configural associations in discrimination learning. Two accounts for the way in which these associations exert their influence are considered.

Animals↗
PubMed1976

Fornix damage enhances successive, but not simultaneous, object-discrimination learning in cats.

The purpose of this study was to compare the effects of fornix lesions with the deficits known to follow septum lesions in cats learning visual object discriminations. In Experiment 1 when eight cats with aspiration lesions of the fornix performed successive discrimination problems, acquisition was greatly facilitated, but first- and second-reversal scores were normal by comparison with eight normal cats and two operated corpus callosum-control cats without fornix damage. Four corpus callosum-damaged cats with secondary degeneration in the medial fornix also learned the initial problem faster than normals. In Experiment 2 in a simultaneous paradigm, eight cats with fornix lesions scored like five normal controls, although they perseverated in early stages of reversal problems. The authors hypothesize that medial fornix damage, in contrast with septum lesions, enhances both initiation and maintenance of response inhibition.

Afferent Pathways↗
PubMedDate not supplied

Visual discrimination learning in binocularly deprived cats: 20 years of studies in the Nencki Institute.

Data obtained by the author and his colleagues on various forms of visual discrimination learning in cats binocularly deprived of pattern vision with cloth masks (BD cats) are reviewed. In these studies two comparison groups were used: controls reared also in the laboratory but with open eyes (C cats) and cats reared in normal environment outside the laboratory (N cats). Data from other laboratories on lid-sutured and dark-reared BD cats are also shortly reviewed. The BD cats showed several clear-cut deficits. Those in pattern discrimination and in fine contrast discrimination were presumably mainly due to impairment of the perceptual inhibitory learning, whereas those in coping with the partition in the apparatus and in successive discrimination were due to impairment of associative inhibitory learning. The deficits in object discrimination and in interocular transfer were apparently due to a reduced number of binocular neurons in the deprived visual cortex and superior colliculi. Dramatic deficit in relearning after ablation of the superior colliculi-pretectum complex shows a reduced utilization of the abnormal cortex in discrimination learning. The C cats shared fully with BD cats a dramatic impairment in the visually delayed response. This short-term memory deficit was presumably due to a limited practice in visual learning in cage-reared cats. The C cats showed also some impairment in coping with the partition and in relearning after the colliculus-pretectum ablation. The BD cats were not impaired in pattern vs. no-pattern discrimination and in grating discrimination. Thus, visual deprivation does not impair the formation of excitatory and simple inhibitory connections required in crude discrimination. Moreover, presumably due to their less distractibility by external stimuli, the BD cats could be even superior to N and C cats in very crude discrimination tasks.

Animals↗
PubMed1989

The role of homecage environmental stimuli in the facilitation of shock-motivated spatial discrimination learning in rat pups.

In three experiments we examined the role of homecage environmental stimuli on learning an aversively motivated spatial discrimination task in 11-day-old rats. Varying the presence and absence of nest shavings in the correct and incorrect arms of a T-maze in Experiment 1 revealed that nest shavings had both nondirective facilitation and approach-eliciting properties. Training the 11-day-old rats in the presence or absence of shavings over three daily sessions and comparing their performance on the third day of training with that of a maturation control in Experiment 2 indicated that there is a residual training effect of the approach-eliciting property of nest shavings on shock-escape behavior. In Experiment 3, using nest shavings either as an irrelevant stimulus or as a redundant relevant cue in an aversively motivated T-maze reversal task suggested that 11-day-old rats acquire the discrimination task using non-nest spatial or directional cues as well as those provided by nest shavings. Overall, these results suggest that nest shavings introduced into aversively motivated tasks create a learning environment comparable to that of appetitively motivated instrumental tasks utilizing suckling from an anesthetized dam as a reinforcer.

Animals↗
PubMed1984

The role of response-reinforcer relationship in discrimination learning of mentally retarded persons.

The role of the spatial relationship between target responses and reinforcers in the discrimination learning of mentally retarded subjects was evaluated. On each training trial, subjects were instructed to move a hand-operated manipulandum to a positive stimulus located at the left or right end of a track. Correct responses were immediately followed by onset of a light and presentation of an edible reinforcer. In the control condition the light and edible reinforcers were presented in a single location equidistant from the ends of the manipulandum track; in the experimental condition, they were presented directly adjacent to the terminus of the response at the end of the manipulandum track corresponding to the location of the correct stimulus. Results showed that discrimination performance was more efficient in the experimental condition than in the control condition.

Adult↗
PubMed1988

The contribution of the rewarded and the non-rewarded stimulus in visual discrimination learning in mice.

The relative contribution of the rewarded and non-rewarded stimulus in the learning of a visual discrimination task in various species is unclear. A number of different parameters have been suggested as influencing the importance of the one over the other, among them the type of reinforcement. Our results show that with both positive reinforcement (using water as reward after a correct choice, and no reinforcement after an incorrect choice) and negative reinforcement (electroshock punishment after an incorrect choice) mice use the position of the incorrect stimulus as a cue for the discrimination. Mice trained by positive reinforcement without the added negative reinforcement of blocking the door on which the incorrect stimulus is projected, do not learn a brightness discrimination task. This suggested that the added negative reinforcement of the closed door had a strong influence on the learning behaviour in our experiments.

Animals↗
PubMed1977

Neurobehavioral and systemic effects of longterm blood lead-elevation in rats. I. Discrimination learning and open field-behavior.

In order to assess neurobehavioral deficit subsequent to early low-level lead-exposure, Wistar-rats were prenatally Pb-exposed via their mothers, neonatally via their dams' milk, and later on via their diet containing lead acetate (745 mg Pb/kg diet). Blood-lead levels (PbB) of dams increased from 24.2-31.2 microgram-% during pregnancy and suckling-periods, those of offsprings were 26.6 microgram-% at about 16 days of age and 28.5 microgram-% at about 190 days of age. Between 100 and 200 days of age 40 male offsprings were subjected to behavioral testing, namely an open field-test and a visual discrimination-learning task. Two learning-tasks of different complexity, i.e. orientation- and size-discrimination, were used. Data of 20 lead-treated animals were compared with those of 20 age-matched controls. In the open-field test lead-fed animals were significantly more restless than controls; an increase of ambulation, rearing and grooming was observed. In the difficult learning-task, i.e. size discrimination, only the controls did learn the problem, whereas only one of the lead-group did; there was, however, no difference between lead- and control-animals for the easy task, i.e. orientation-discrimination. The observed effects, namely overreaction in the open field and a deficit of visual discrimination learning, may be interpreted in terms of lead-induced CNS-dysfunction. They clearly suggest that the "no-response level" for neurobehavioral damage in the rat, subsequent to early lead-exposure, must be assumed to be lower than 35 microgram/100 ml.

Animals↗
PubMed1976

Differential effects of chlordiazepoxide on simultaneous and successive brightness discrimination learning in rats.

Chlordiazepoxide (CDP) at a dose of 20 mg/kg, i.p. was found to exert a marked disruptive effect on black-white successive discrimination learning in rats, while this effect failed to be obtained on black-gray simultaneous discrimination. Since trials to the learning criterion were found almost equal for saline rats on both successive and simultaneous discrimination tasks, the differential inhibitory effects of CDP could not be accounted for in terms of differences in difficulties of the two tasks. It is suggested that present results might be interpreted in terms of the hypotheses (a) that CDP produces a deficit in the integration of relevant stimulus cues when they were presented across trials or (b) that CDP has a disinhibitory effect in that inhibition of dominant response (positional preference) patterns is weakened by the drug, in a manner similar to effects observed in hippocampectomized animals.

Animals↗