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PubMedDate not supplied

The effect of beta-(Tyr9)melanotropin-(9-18) on active avoidance behavior, electroconvulsive shock-induced amnesia and T-discrimination learning of rats.

The effect of beta-(Tyr9)melanotropin-(9-18) was investigated on active avoidance behavior, electroconvulsive shock (ECS)-induced amnesia and T-discrimination learning in rats. The decapeptide inhibited the extinction of active avoidance behavior. It was also able to block ECS-induced amnesia if the treatment was performed immediately, or 4 hr or 20 hr after the ECS. In the T-discrimination paradigm the peptide facilitated spatial discrimination learning and reversal learning. These results suggest that beta-(Tyr9)melanotropin-(9-18) can influence learning and memory processes in different behavioral tests.

Amnesia↗
PubMed1989

A role for stimulus generalization in conditional discrimination learning.

In each of three experiments on discrimination learning by rats, whether or not a 10-sec target stimulus was followed by food was determined by the nature of a 2-min background stimulus that accompanied it. A conditional discrimination was employed in Experiment 1 such that background A indicated food would follow one target but not the other, whereas this relationship between the targets and food was reversed in the presence of background B. Experiment 2 employed two feature-positive discriminations. Subsequent test trials revealed that the background for one discrimination was able to enhance responding during the target for the other discrimination. Experiment 3 employed a feature-positive and a feature-negative discrimination prior to test trials in which each target was presented separately during a compound of both background stimuli. The compound enhanced responding to the target from the feature-positive discrimination and reduced it to the target from the feature-negative discrimination. We suggest that to accommodate all these findings, the best explanation is provided by a configural model of Pavlovian conditioning.

Animals↗
PubMed1998

The role of the central cholinergic projections in cognition: implications of the effects of scopolamine on discrimination learning by monkeys.

In humans, administration of the cholinergic antagonist scopolamine impairs the encoding of information into long-term memory and has effects on other cognitive processes. It has been supposed that it is inhibition of the rising cholinergic projections from the basal forebrain, specifically from the basal nucleus of Meynert (NBM) to the neocortex and from the medial septum/vertical limb of the diagonal band of Broca (MS/VDB) to the hippocampus, that results in these cognitive impairments. In this paper, we describe the effects of scopolamine treatment in monkeys on learning different sorts of visual discrimination and visuospatial conditional tasks and compare these results to the effects of lesions of the rising cholinergic projections. Experiments in rodents in which these projections have been selectively destroyed have failed to produce a consensus view of the functions of these two areas. In particular, highly specific immunotoxic lesions of the NBM have largely failed to produce changes in task performance that can be interpreted as resulting from a cognitive impairment. In monkeys, lesions of the NBM produce modest or short-lasting, impairments in visual discrimination learning, retention, and reversal, whereas lesions of the MS/VDB produce large and permanent impairments of certain types of conditional learning. Similar impairments produced by scopolamine in monkeys and additive effects of lesions of the NBM or MS/VDB with scopolamine suggest that scopolamine has these effects by acting on the rising cholinergic pathways rather than on other cholinergic systems in the brain. It is argued that the rising cholinergic projections sustain the functions of the target areas; in the case of the hippocampus in humans, the function is usually regarded as being the analysis of information in a way that is pertinent to the formation of episodic memories and in the case of the neocortex, is the analysis of information in a manner that is relevant to the cognitive processing of on-going events and the acquisition of semantic knowledge.

Acetylcholine↗
PubMed1980

Conditional discrimination learning: a critique and amplification.

Carter and Werner recently reviewed the literature on conditional discrimination learning by pigeons, which consists of studies of matching-to-sample and oddity-from-sample. They also discussed three models of such learning: the "multiple-rule" model (learning of stimulus-specific relations), the "configuration" model, and the "single-rule" model (concept learning). Although their treatment of the multiple-rule model, which seems most applicable to the pigeon data, is generally excellent, their discussion of the other two models is incomplete and sometimes inaccurate. Potential problems of terminology are discussed in the present paper, as are additional lines of research that deserve consideration by those interested in further work in this area. The issue of response versus stimulus selection (configuration versus compound-cue learning) is discussed in connection with the configuration model. Particular attention is given to Carter and Werner's criticism of the application, in studies with other species, of the learning set procedure in testing for single-rule learning. Some of the important related issues are: the bias for improvement on new problems in a series, the adequacy of a multiple-rule model to explain learning set formation, and evidence in favor of the single-rule model, at least in primates. Consideration of these additional contributions to the study of conditional discrimination learning emphasizes the usefulness of this task in the comparative study of cognitive processes.

Animals↗
PubMed2006

Postnatal exposure to diisopropylfluorophosphate enhances discrimination learning in adult mice.

Visual discrimination and reversal learning were tested in adult C57Bl/6 mice that had been treated on postnatal days (PND) 4-10 with diisopropylfluorophosphate (DFP), an acetylcholinesterase inhibitor. DFP-treated mice attained the learning criterion in the Y maze significantly earlier than saline-treated mice. Female mice treated with DFP showed a more rapid decline in errors in the initial discrimination task, compared to female mice treated with saline. There was no effect of DFP treatment on learning the reverse discrimination. The data suggest that long-lasting effects of treatment with an acetylcholinesterase inhibitor can improve discrimination learning, similarly to the improvement reported by acute administration in adults.

Animals↗
PubMed1999

Discrimination learning of amplitude modulated tones in Mongolian gerbils.

Discrimination learning of 100% sinusoidal amplitude modulated tones (AM) was investigated in adult Mongolian gerbils using a footshock motivated shuttle box avoidance go/no go paradigm. AM stimuli to be discriminated had identical carrier frequency (2 kHz) but differed in modulation frequency (fm) by one octave. Six groups of gerbils were trained to discriminate AM-pairs with fm ranging from 10 to 640 Hz. Learning proceeded faster and discrimination performance was slightly better for low fm, up to 80 Hz, than for high fm, above 80 Hz. These results may be related to cortical AM encoding (Schulze, H. and Langner, G., J. Comp. Physiol. A, 181 (1997) 651-663), which is temporal for low fm (synchrony code) and spatial for high fm (rate-place code). This may implicate different neuronal learning strategies or distinct behavioral meanings influencing the discrimination training.

Acoustic Stimulation↗
PubMed2006

Vicarious trial-and-error behavior and hippocampal cytochrome oxidase activity during Y-maze discrimination learning in the rat.

The present study investigated whether more vicarious trial-and-error (VTE) behavior, defined by head movement from one stimulus to another at a choice point during simultaneous discriminations, led to better visual discrimination learning in a Y-maze, and whether VTE behavior was a function of the hippocampus by measuring regional brain cytochrome oxidase (C.O.) activity, an index of neuronal metabolic activity. The results showed that the more VTEs a rat made, the better the rat learned the visual discrimination. Furthermore, both learning and VTE behavior during learning were correlated to C.O. activity in the hippocampus, suggesting that the hippocampus plays a role in VTE behavior during discrimination learning.

Analysis of Variance↗
PubMed1980

Classification of abnormal children: discrimination learning ability.

Large individual differences exist among psychotic and retarded children, and a procedure that would enable classification of discrimination learning ability would be of value. A procedure designed to assess the discrimination learning thresholds of low-functioning children is described. A performance index (PI) that reflects accuracy of discriminative responding, difficulty of the discriminations attained, and learning rate was found to correlate significantly with mental age, intelligence quotient, Vineland Social Age, Vineland Social Quotient, and language functioning, but not with chronological age. The question of the optimal magnitude of correlation between a new measure and existing measures is discussed.

Autistic Disorder↗
PubMed1980

Damages to cortical associative areas: effects on visual discrimination learning in cats.

Participation of the parietal and frontal cortical areas in pattern discrimination learning was studied in cats. Extirpation of the parietal cortex (fields 5 or 7) produced a deficit of visual discrimination of simultaneously presented patterns, but the animals were able to relearn the task. Postoperative learning of simultaneous discrimination was abolished, although successive discrimination of the same stimuli was still possible. The parietal associative areas probably participate in the organization of spatially and visually controlled movements. The frontal lobe ablation eliminated pattern but not brightness discrimination learning. The lesion of the frontal lobe is apparently connected with the occulomotor mechanism of pattern discrimination.

Animals↗
PubMed1993

Simultaneous visual discrimination learning in lurcher mutant mice.

Lurcher mutants were evaluated in the acquisition of a visual discrimination learning task with water escape as a reward. In comparison to normal mice, lurchers were impaired in discrimination learning in a manner not explainable by motor deficits. Although in initial trials the mutants had difficulty in finding the correct invisible platform, in agreement with previous findings of deficits in visuo-spatial organization, they eventually were able to find the quadrants where one of two platforms was situated but even so took longer to reach criterion in choosing the correct one. These results agree with the hypothesis that the cerebellum is involved in the acquisition of visual discrimination tasks in mice.

Animals↗
PubMed1981

Concurrent discrimination learning of monkeys after hippocampal, entorhinal, or fornix lesions.

Ablations of anterior inferotemporal cortex in monkeys are known to impair learning when discriminations between members of several pairs of objects are taught concurrently. This deficit has been attributed to a loss of visual mnemonic functions. But ablations of hippocampus have also been shown to impair retention, and this impairment transcends the visual modality. Therefore, in the first of two experiments, we compared the behavioral effects of inferotemporal cortical lesions with those of either hippocampus, entorhinal area, or fornix, using a visual concurrent discrimination task. Monkeys with either hippocampal or entorhinal ablations were impaired, while those with fornix sections were not. However, ablations of hippocampus included inadvertent damage of the inferotemporal cortex. Therefore, in the second experiment, behavioral effects of inferotemporal lesions were compared with those of hippocampus (without additional inferotemporal damage) on the concurrent task in both visual and tactual modalities. In the visual mode, monkeys with hippocampal removals were as impaired as those with inferotemporal ablations. In the tactual mode, however, hippocampal, but no inferotemporal, ablations were followed by a deficit. Our results, taken together with other existing evidence, emphasize the role of the hippocampus in mediating associative learning in more than one modality. These results, obtained with non-human primates, are in line with clinical findings.

Animals↗
PubMed2003

The role of perirhinal cortex in visual discrimination learning for visual secondary reinforcement in rats.

Perirhinal cortex in monkeys has been thought to be involved in visual associative learning. The authors examined rats' ability to make associations between visual stimuli in a visual secondary reinforcement task. Rats learned 2-choice visual discriminations for secondary visual reinforcement. They showed significant learning of discriminations before any primary reinforcement. Following bilateral perirhinal cortex lesions, rats continued to learn visual discriminations for visual secondary reinforcement at the same rate as before surgery. Thus, this study does not support a critical role of perirhinal cortex in learning for visual secondary reinforcement. Contrasting this result with other positive results, the authors suggest that the role of perirhinal cortex is in "within-object" associations and that it plays a much lesser role in stimulus-stimulus associations between objects.

Animals↗
PubMedDate not supplied

Sound sequence discrimination learning motivated by reward requires dopaminergic D2 receptor activation in the rat auditory cortex.

We have previously reported that sound sequence discrimination learning requires cholinergic inputs to the auditory cortex (AC) in rats. In that study, reward was used for motivating discrimination behavior in rats. Therefore, dopaminergic inputs mediating reward signals may have an important role in the learning. We tested the possibility in the present study. Rats were trained to discriminate sequences of two sound components, and licking behavior in response to one of the two sequences was rewarded with water. To identify the dopaminergic inputs responsible for the learning, dopaminergic afferents to the AC were lesioned with local injection of 6-hydroxydopamine (6-OHDA). The injection attenuated sound sequence discrimination learning, while it had no effect on discrimination between the sound components of the sequence stimuli. Local injection of 6-OHDA into the nucleus accumbens attenuated sound discrimination learning. However, not only discrimination learning of sound sequence but also that of the sound components were impaired. SCH23390 (0.2 mg/kg, i.p.), a D1 receptor antagonist, had no effect on sound sequence discrimination learning, while it attenuated the licking behavior to unfamiliar stimuli. Haloperidol (0.5 mg/kg, i.p.), a D2 family antagonist, attenuated sound sequence discrimination learning, while it had no clear suppressive effect on discrimination of two different sound components and licking. These results suggest that D2 family receptors activated by dopaminergic inputs to the AC are required for sound sequence discrimination learning.

Acoustic Stimulation↗
PubMed2005

Visual discrimination learning in zebrafish (Danio rerio).

Three experiments demonstrated visual discrimination learning in zebrafish (Danio rerio). In each experiment, zebrafish were given a choice between two visually distinct arms of a T-maze. Choice of one stimulus was always followed by a food reward, but choice of the other stimulus was not rewarded. Different colored sleeves fitted around the arms of the T-maze were used in Experiments 1 (green and purple) and 2 (red and blue). The stimuli used in Experiment 3 were white sleeves lined with horizontal or vertical black stripes. In all three experiments, zebrafish acquired a significant preference for the stimulus that led to a food reward. Experiments 1 and 2 also showed that zebrafish could learn a reversal of the discrimination. Finally, the effect of discontinuing food rewards was examined after reversal training in Experiment 2 and after initial discrimination training in Experiments 1 and 3. Non-reinforcement led to a decrease in correct responding in Experiments 2 and 3 independent of stimulus identity, but to an asymmetrical pattern of responding in Experiment 1. The median latency to make a choice response decreased over the course of acquisition in all three experiments; during extinction, median response times did not change at all in Experiment 1 and increased only very slightly in Experiment 2, but showed a substantial increase in Experiment 3. The implications of these results for the zebrafish as a model system for genetic studies of learning and memory are discussed.

Animals↗
PubMed2002

Landmark discrimination learning in the dog: effects of age, an antioxidant fortified food, and cognitive strategy.

The landmark discrimination learning test can be used to assess the ability to utilize allocentric spatial information to locate targets. The present experiments examined the role of various factors on performance of a landmark discrimination learning task in beagle dogs. Experiments 1 and 2 looked at the effects of age and food composition. Experiments 3 and 4 were aimed at characterizing the cognitive strategies used in performance on this task and in long-term retention. Cognitively equivalent groups of old and young dogs were placed into either a test group maintained on food enriched with a broad-spectrum of antioxidants and mitochondrial cofactors, or a control group maintained on a complete and balanced food formulated for adult dogs. Following a wash-in period, the dogs were tested on a series of problems, in which reward was obtained when the animal responded selectively to the object closest to a thin wooden block, which served as a landmark. In Experiment 1, dogs were first trained to respond to a landmark placed directly on top of coaster, landmark 0 (L0). In the next phase of testing, the landmark was moved at successively greater distances (1, 4 or 10 cm) away from the reward object. Learning varied as a function of age group, food group, and task. The young dogs learned all of the tasks more quickly than the old dogs. The aged dogs on the enriched food learned L0 significantly more rapidly than aged dogs on control food. A higher proportion of dogs on the enriched food learned the task, when the distance was increased to 1cm. Experiment 2 showed that accuracy decreased with increased distance between the reward object and landmark, and this effect was greater in old animals. Experiment 3 showed stability of performance, despite using a novel landmark, and new locations, indicating that dogs learned the landmark concept. Experiment 4 found age impaired long-term retention of the landmark task. These results indicate that allocentric spatial learning is impaired in an age-dependent manner in dogs, and that age also affects performance when the distance between the landmark and target is increased. In addition, these results both support a role of oxidative damage in the development of age-associated cognitive dysfunction and indicate that short-term administration of a food enriched with supplemental antioxidants and mitochondrial cofactors can partially reverse the deleterious effects of aging on cognition.

Age Factors↗
PubMed1988

Binocularly deprived cats are normal in visual discrimination learning in a simple apparatus.

Pattern discrimination learning was compared in three groups of cats: reared in normal conditions, reared in the laboratory with opened eyes, and deprived of patterned vision from birth. A four-choice apparatus without partitions was used. The figure of a disc was reinforced with food, whereas a cross, triangle and square were not. All groups reached criterion after similar numbers of trials and errors, indicating that in binocularly deprived cats, simple perceptual and associative learning are not impaired.

Animals↗