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PubMed1999

Comparative effects of prenatal and postnatal undernutrition on learning and memory in rats.

Effects of pre- and post-natal undernutrition on learning and memory parameters were studied in albino rats. Prenatal undernutrition was induced in rat pups by restricting the mother's diet by 50% during the entire gestation period, whereas postnatal undernutrition was induced in rat pups by restriction of their diet by rotating them between lactating and non-lactating maternalised females for 12 hr each day during suckling period from 2nd day to 18th day after birth. At 2.5 to 3 months of age all the rat offsprings were subjected to (i) original and reversal discrimination learning, (ii) passive avoidance, and (iii) active avoidance and its retention tests. The results indicate that both pre- and post-natal undernutrition in rat pups caused significant deficits in original and reversal discrimination learning, retention of passive avoidance after one week retention interval, and retention of active of avoidance learning. However, both pre- and post-natal undernutrition did not show significant effect on acquisition of active avoidance and retention of passive avoidance after 24 hr retention interval.

Animals↗
PubMed2005

Behavioural and cognitive effects of oligofructose-enriched inulin in rats.

The behavioural and cognitive effects of oligofructose-enriched inulin at the doses of 5 and 10 % in the diet, orally ingested daily during 2 weeks, were investigated using a functional observational battery (FOB) and the light extinction test in male Wistar rats. Control rats received a standard diet and were tested in the same test situations. The behavioural effects were assessed 2 d before and 14 d after the beginning of the treatment period and the cognitive effects were investigated after the administration period by lever-pressing activity and learning discrimination using the light extinction test paradigm. In general, the study demonstrated that oligofructose-enriched inulin at 5 % in the diet, and particularly at 10 % in the diet, caused relaxing-like effects, stimulated and increased the general activity and interest of the rats to the test environment. In addition, both doses of oligofructose-enriched inulin showed significant effects on learning discrimination in male rats, in comparison with the control diet. These results suggest that oligofructose-enriched inulin, particularly at the dose of 10 %, improves cognitive performances in the light extinction test and the well-being of male rats using the FOB.

Animals↗
PubMed1993

Critical determinants of nonspatial working memory deficits in rats with conventional lesions of the hippocampus or fornix.

Rats with conventional lesions of the hippocampus or fornix were compared postoperatively with controls on nonspatial memory tasks. Neither lesion impaired delayed matching-to-sample (DMS) performance in a discrete-trial task involving "pseudo-trial-unique" complex stimuli. An impairment emerged if a single pair of complex stimuli was used throughout each day's session, and the greatest impairment was obtained with the use of a single pair of less complex stimuli throughout each day's test. Transfer to a continuous DMS task with no explicit intertrial interval produced a different pattern because both lesion and control levels of performance were depressed when two complex stimuli were used repeatedly. A final, separate discrimination learning experiment showed that hippocampectomized rats readily discriminated between the stimuli associated with the greatest lesion-induced DMS deficit. Hippocampal dysfunction thus produces clear deficits on non-spatial memory tasks under appropriate test conditions.

Animals↗
PubMed2004

Cognitive inflexibility after prefrontal serotonin depletion.

Serotonergic dysregulation within the prefrontal cortex (PFC) is implicated in many neuropsychiatric disorders, but the precise role of serotonin within the PFC is poorly understood. Using a serial discrimination reversal paradigm, we showed that upon reversal, selective serotonin depletion of the marmoset PFC produced perseverative responding to the previously rewarded stimulus without any significant effects on either retention of a discrimination learned preoperatively or acquisition of a novel discrimination postoperatively. These results highlight the importance of prefrontal serotonin in behavioral flexibility and are highly relevant to obsessive-compulsive disorder, schizophrenia, and the cognitive sequelae of drug abuse in which perseveration is prominent.

5,7-Dihydroxytryptamine↗
PubMed1966

Behavioral contrast and the peak shift: effects of extended discrimination training.

Behavioral contrast and the peak shift, two widely observed phenomena in experiments on successive discrimination learning, were shown to disappear during extended discrimination training. This finding and an analysis of the conditions under which behavioral contrast and the peak shift occur suggested that both phenomena were by-products of emotional responses that resulted from response suppression and that their disappearance after extended discrimination training could be attributed to the dissipation of such emotional responses.

Animals↗
PubMed1997

Hippocampal degeneration inducing impairment of learning in rats: model of dementia?

In the pharmacological field, the development of drugs effective for dementia is now widely anticipated because of the increase in the elderly population. Dementia has some histological degeneration in the brain, including the hippocampus. Preclinical evaluations of such drugs use animal models with memory impairment, since memory impairment is a major criterion of dementia. We therefore investigated two animal models with hippocampal degeneration. Neonatal administration of monosodium glutamate (MSG) induced specific degeneration of hippocampal pyramidal cells in the CA1 region of Wistar rats in adulthood. In these animals, the correct response rate during the acquisition period of light-dark discrimination learning was significantly lower than that in the control group. No significant changes were noted in the hippocampal concentrations of neurotransmitter substances, including acetylcholine and glutamate. In the second model, similar histological changes were observed at 3 weeks after oral administration of trimethyltin (TMT). These histological changes were accompanied by a reduction in the intrahippocampal concentrations of acetylcholine and glutamate. In the case of light-dark discrimination learning, neither pre- nor post-training administration of TMT affected the correct response rate during both the acquisition and retention test periods. In the case of 8-arm radial maze learning, the increase in correct response rate was significantly suppressed in comparison with that of the control group when TMT was administered at 4 weeks before starting the acquisition trial. This suppression was followed by a lower response rate in the retention test. On the other hand, the correct response rates in retention tests were not affected when TMT was administered after completion of the acquisition trial. These findings indicate that sole degeneration of the hippocampus was able to induce different types of memory impairment, and single evaluation of a drug with one learning paradigm was difficult to justify that a drug is effective for dementia.

Animals↗
PubMed1989

Facilitation of acquisition and retention in preweanling but not postweanling rats by the presence of familiar home-nest material.

A series of four experiments examined the effect of the presence of stimuli from the home nest on the acquisition and retention of aversively motivated behaviors in preweanling and adult rats. In Experiment 1, training in the presence of home-nest shavings facilitated acquisition of a T-maze discrimination to escape footshock for 16-day-old rats but not for adults. Experiment 2 demonstrated that the extent to which preweanlings were familiar with the home shavings determines the degree to which these stimuli facilitate spatial discrimination learning. When clean shavings were made more familiar than soiled home-nest stimuli (by changing the shavings every day) clean shavings enhanced discrimination performance, whereas no enhancement of learning by home shavings was observed. Experiment 3 extended the generality of the enhancement effect to a conditioned location aversion and examined the extent to which this facilitative effect was due to the tendency for home-nest shavings to elicit approach responses. Expression of the conditioned aversion was enhanced in subjects conditioned in the presence of home shavings, regardless of whether the home shavings were presented with the CS+, the CS-, or both. Experiment 4 determined that the enhanced expression of learning in the context of home-nest stimuli observed for preweanlings did not occur among subjects trained shortly after weaning. Collectively, these data suggest that whereas the enhancement of learning and retention by familiar home-nest stimuli enjoys generality across a number of conditioning situations, the effect may be limited to a relatively brief period during ontogeny.

Aging↗
PubMed1986

Perceptive properties of the multi-site electrical microstimulation of the olfactory bulb in the rat.

Electrical microstimulation of the olfactory bulb in different locations has been shown to provide water-deprived rats with discriminative cues for selecting a palatable solution without tasting it in a two-choice test. Some perceptive properties of bulbar electrical stimulation were investigated. It was shown that the perceptive effect evoked by stimulating a given site could be recognized when this site was stimulated together with several others. The animals' perception of multi-site stimulation patterns seems therefore to be analytical rather than synthetic. Discrimination of stimulation patterns did not require presentation of concurrent patterns inside a short time interval. Identification of a multi-site pattern was possible when this pattern was presented alone in a test session. Individual characteristics of bulbar microstimulation appear to be perceived absolutely rather than differentially. A good retention of the discrimination learning of specific stimulation patterns was observed. Animals could identify stimulation patterns after complete interruption of the training for 17 days. The results are discussed with reference to the properties of the natural stimulation of the olfactory system.

Animals↗
PubMed1983

Influence of exteroceptive contextual conditions upon internal drug stimulus control.

Rats were trained in a spatial T-maze discrimination either in a drugged (D = pentobarbital, 17.5 mg/kg) or in a non-drugged (N = saline) state (drug discrimination learning). Either of two external discriminative stimulus sets (light vs complete darkness) was consistently associated with the D or N state. When tested in the presence of the external stimulus previously associated with training in the D state, the animals made more drug-appropriate choices when tested with low pentobarbital doses as compared to testing in the external stimulus condition previously associated with the N state. This was reflected both in the ED50 values and the slopes of the dose-generalization gradients. The gradients of the controls were intermediate to those of the experimental rats. The present data suggest a new approach for studying interactions between controlling features in environmental events and the internal state.

Animals↗
PubMed1998

Associative mediational processes in the acquired equivalence and distinctiveness of cues.

Three experiments used rats to examine the acquired equivalence or distinctiveness of cues occurring when 2 auditory and 2 visual stimuli were associated with either the same or with different reinforcing outcomes (A1+, A2+, V1*, and V2* vs. A1+, A2*, V1+, and V2*). Subsequent single modality discrimination learning (e.g., A1+, A2-) was assessed in Experiment 1, whereas in Experiment 2, visual and auditory discriminations were tested concurrently (i.e., A1+, A2-, V1-, V2*). In Experiment 3, auditory and visual discriminations (A1+, A2-, V1-, V2*) were trained and then reversed, using either the same (A1-, A2+, V1*, V2-) or different outcomes (A1-, A2*, V1+, V2-) within each stimulus modality. Discriminations were learned more rapidly in these studies when different outcomes were associated with stimuli from the same modality. These results challenge associative mediational theories of acquired equivalence and distinctiveness.

Animals↗
PubMed1971

Contrast and stimulus generalization following prolonged discrimination training.

Different groups of pigeons received discrimination training in which the reinforcement-associated and extinction-associated stimuli were respectively either (a) a line tilt vs a blank key, (b) a blank key vs a line tilt, or (c) two different line tilts. The high response rates that developed to the positive stimulus in all groups during discrimination learning were maintained over 64 sessions of training. After these sessions, all subjects were tested for stimulus generalization along the line-tilt dimension. Gradients of relative (per cent) generalization around the stimulus associated with reinforcement (so-called excitatory gradients) and around the stimulus associated with extinction (so-called inhibitory gradients) were as steep as they typically are after much briefer training periods. These results do not support several of Terrace's predictions on the basis of the hypothesis that emotional responses develop to the stimulus associated with extinction during discrimination learning with errors, but eventually dissipate after extended training.

Journal Article↗
PubMed1991

The basal forebrain-cortical cholinergic system: interpreting the functional consequences of excitotoxic lesions.

Ibotenic acid and kainic acid lesions of the basal forebrain induce profound deficits in performance on a wide variety of tasks involving discrimination learning and memory. These observations have been widely taken to reflect damage of cholinergic projections from the nucleus basalis magnocellularis (NBM) to the neocortex, and to provide an animal model of dementia. However, injections of the toxins quisqualic acid and, more recently, alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) into the same site, which produce at least as extensive cholinergic cell loss, induce only marginal impairments on the same range of cognitive tasks. Further analysis suggests that the cholinergic regulation of the neocortex may influence specific aspects of discrimination learning and visual attention. Conversely, we propose that many of the functional consequences of ibotenic acid lesions on mnemonic tasks cannot be attributed to disruption of basal forebrain cholinergic systems, but may instead result from damage in the globus pallidus to corticostriatal output pathways.

Animals↗
PubMed1979

Food delivery as a conditional stimulus: Feature-learning and memory in pigeons.

Three experiments investigated the learning and memory of discriminations based on presence versus absence of a pre-trial food delivery. In Experiment 1 half the illuminations of a response key were followed by food regardless of the subject's behavior. In one group an extra food delivery preceded only reinforced trials (feature-positive condition), whereas in a second group it preceded only nonreinforced trials (feature-negative condition). Key pecks and approaches revealed more rapid and superior discrimination learning in the first group. Experiment 2 replicated the results of Experiment 1 but yielded no evidence that greater "unexpectedness" of pretrial food conditions facilitates discriminative performance. In Experiment 3, individual pigeons trained on a conditional discrimination exhibited a within-subject feature-positive superiority. Delay between pretrial and trial stimuli interacted with feature-positive versus feature-negative training in both the between-group (Experiment 2) and within-subject (Experiment 3) procedures: performance was decremented at both short and long delays in the feature-positive condition but was decremented only at longer delays in the feature-negative condition. The feature-positive superiority obtained here is incompatible with explanations based on either the general concept of "perceptual organization" or on the conditional nature of feature-negative discriminations.

Journal Article↗
PubMed1989

Selective sparing after lesions of visual cortex in newborn kittens.

Previous findings are discordant regarding the effects of perinatal lesions of Cortical Areas 17 and 18 on visual discrimination learning in cats. Three potential determinants of such sparing were investigated: age at lesion (4 or 181 days), age at testing (3 or 9 months), and stimulus complexity. Age at testing was not significant, but performance varied with stimulus complexity and cortical damage, and there was an interaction between stimulus complexity and age at lesion. Both operated groups were transiently impaired in discriminating objects and subsequently learned to discriminate simple 2-dimensional patterns as well as done by controls, but the lesion groups were permanently impaired in discriminating similar patterns circumscribed by irrelevant lines. The age-at-lesion groups differed, however, in discriminating patterns masked by superimposed lines. The group lesioned at 181 days was severely impaired at both acquisition and subsequent intercurrent performance; the group lesioned at 4 days was impaired only at intercurrent performance. This study suggests that sparing after early postnatal damage of Areas 17 and 18 occurs only under limited circumstances.

Animals↗
PubMed1987

Effect of dietary alpha-linolenate/linoleate balance on brain lipid compositions and learning ability of rats.

Spontaneously hypertensive rats (SHR) and normotensive control, Wistar/Kyoto (WKY) rats through two generations were fed a semipurified diet supplemented either with safflower oil (rich in linoleate) or with perilla oil (rich in alpha-linolenate). The cerebral lipid contents and phospholipid compositions did not differ between the two dietary groups of SHR rats. There were also no differences in the unsaturated/saturated ratios of individual phospholipids or the proportions of plasma-logens. However, the proportions of (n-3) and (n-6) fatty acids were significantly different. Decreases in the proportions of docosahexaenoate [22:6 (n-3)] in phosphatidylethanolamine and phosphatidylserine in the safflower oil group were compensated for with increases in the proportions of docosatetraenoic [22:4 (n-6)] and docosapentaenoic [22:5 (n-6)] acids as compared with the perilla oil group. These differences in phospholipid acyl chains were much smaller than the difference in the proportions of linoleate and alpha-linolenate of the diets. In a brightness-discrimination learning test, the total number of responses to the positive and negative stimuli were less in the groups fed perilla oil. However, the alpha-linolenate-deficient group took longer to decrease the frequency of R- responses and therefore longer to learn the discrimination. Consequently, the correct response ratios were higher in the perilla oil groups than in the safflower oil groups. Thus, the dietary alpha-linolenate/linoleate balance influenced the (n-3)/(n-6) balance of polyenoic fatty acids differently among brain phospholipids.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

The role of observing and attention in establishing stimulus control.

Early theorists (Skinner, Spence) interpreted discrimination learning in terms of the strengthening of the response to one stimulus and its weakening to the other. But this analysis does not account for the increasing independence of the two performances as training continues or for increases in control by dimensions of a stimulus other than the one used in training. Correlation of stimuli with different densities of reinforcement produces an increase in the behavior necessary to observe them, and greater observing of and attending to the relevant stimuli may account for the increase in control by these stimuli. The observing analysis also encompasses errorless training, and the selective nature of observing explains the feature-positive effect and the relatively shallow gradients of generalization generated by negative discriminative stimuli. The effectiveness of the observing analysis in handling these special cases adds to the converging lines of evidence supporting its integrative power and thus its validity.

Animals↗
PubMed1981

Prevention of incorrect responding for establishing instruction following behaviours.

A comparison of two techniques for teaching instruction-following to severely retarded children was the purpose of the present study. The design consisted of a cross-over design involving a cross-over of techniques for each of the three subjects. Within the experimental condition the instructions were presented by physically preventing the subject from making an incorrect response, that is, interrupting an incorrect movement. The results were in favour of the experimental condition in comparison with a trial-and-error approach. The data obtained in this investigation provide further evidence for the notion of errorless-discrimination learning.

Child↗
PubMed1994

Context specificity of conditioned-reinforcement effects on discrimination acquisition.

Pigeons were trained on a series of reversals of a simultaneous form discrimination in which the trial outcomes were separated from the choice responses by an 8-s delay interval. Different conditions were defined by the stimuli occurring during the two halves of the delay interval. Discrimination learning was greatly facilitated by having differential stimuli during the delay following correct versus incorrect choices. When the differential stimuli appeared only at the midpoint of the delay, some facilitation occurred relative to when no different stimuli occurred, but there was substantially less facilitation than when the differential stimuli occurred immediately contingent on choice. A reversed-stimulus condition, in which the stimulus at the onset of the delay following a correct choice was the same as that during the last segment of the delay following an incorrect choice, and the stimulus at the onset of the delay following an incorrect choice was the same as that preceding food during the last segment of the delay following a correct choice, also facilitated discrimination learning relative to the nondifferential stimulus conditions.

Journal Article↗