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PubMed1988

The pretectum and visual discrimination learning in the hooded rat.

In previous studies on the effects of pretectal lesions on visual discrimination performance, the lesions have either been small or their effects confounded with damage to the adjacent thalamus and the results have been inconsistent. This study compares the effects of large pretectal lesions (PRT) with lesions in lateral (TLP) and medial (MPT) posterior thalamus on simultaneous black versus white (BW), horizontal versus vertical (HV) discrimination acquisition and low frequency flicker detection. An unoperated control group treated regularly with a cycloplegic to produce mydriasis was also tested in the discrimination learning phase. PRT lesions and treatment with the cycloplegic produced mydriasis as well as an impairment on BW. Neither group was impaired on HV. Animals with MPT and TLP lesions were impaired on BW and HV and those with TLP lesions were also impaired on flicker detection. It is concluded that the pretectum is important for visual intensity discrimination learning but the effects of lesions are due to disturbances of pupillary control. The significance of this finding for the interpretation of deficits produced by lesions elsewhere in the thalamus is discussed.

Animals↗

PubMed1998

Effects of MK-801 on vicarious trial-and-error and reversal of olfactory discrimination learning in weanling rats.

The effects of dizocilpine maleate (MK-801) on vicarious trial-and-error (VTE), and on simultaneous olfactory discrimination learning and its reversal, were observed in weanling rats. The term VTE was used by Tolman (The determiners of behavior at a choice point. Psychol. Rev. 1938;46:318-336), who described it as conflict-like behavior at a choice-point in simultaneous discrimination learning. It takes the form of head movements from one stimulus to the other, and has recently been proposed by Amsel (Hippocampal function in the rat: cognitive mapping or vicarious trial-and-error? Hippocampus, 1993;3:251-256) as related to hippocampal, nonspatial function during this learning. Weanling male rats received systemic MK-801 either 30 min before the onset of olfactory discrimination training and its reversal, or only before its reversal. The MK-801-treated animals needed significantly more sessions to acquire the discrimination and showed significantly fewer VTEs in the acquisition phase of learning. Impaired reversal learning was shown only when MK-801 was administered during the reversal-learning phase, itself, and not when it was administered throughout both phases.

Animals↗

PubMed2005

Peak shift discrimination learning as a mechanism of signal evolution.

"Peak shift" is a behavioral response bias arising from discrimination learning in which animals display a directional, but limited, preference for or avoidance of unusual stimuli. Its hypothesized evolutionary relevance has been primarily in the realm of aposematic coloration and limited sexual dimorphism. Here, we develop a novel functional approach to peak shift, based on signal detection theory, which characterizes the response bias as arising from uncertainty about stimulus appearance, frequency, and quality. This approach allows the influence of peak shift to be generalized to the evolution of signals in a variety of domains and sensory modalities. The approach is illustrated with a bumblebee (Bombus impatiens) discrimination learning experiment. Bees exhibited peak shift while foraging in an artificial Batesian mimicry system. Changes in flower abundance, color distribution, and visitation reward induced bees to preferentially visit novel flower colors that reduced the risk of flower-type misidentification. Under conditions of signal uncertainty, peak shift results in visitation to rarer, but more easily distinguished, morphological variants of rewarding species in preference to their average morphology. Peak shift is a common and taxonomically widespread phenomenon. This example of the possible role of peak shift in signal evolution can be generalized to other systems in which a signal receiver learns to make choices in situations in which signal variation is linked to the sender's reproductive success.

Adaptation, Biological↗

PubMed1994

Discrimination learning and concept formation in the Arabian horse.

Discrimination learning and concept formation abilities were investigated in four mature Arabian horses. A series of two-choice discrimination problems were presented on stimulus panels that could open to allow access to food bowls. Selection of the correct stimulus resulted in food reinforcement, and an incorrect choice was not rewarded. The positions of the correct and incorrect stimuli were varied randomly during each test session, and the criterion for learning each problem was 85% correct for two consecutive sessions of 30 or 40 trials. Testing progressed through six discrimination problems. The first four were simple pattern discriminations, but the last two incorporated several different triangles as correct stimuli and thus involved the concept of triangularity. Two of the subjects successfully completed only simple pattern discriminations, one showed evidence of learning in the first concept problem, and one completed all six tests, including the two concept formation problems. The results demonstrate complex pattern discrimination ability in horses, and suggest that they may also have the ability to form and use concepts in problem solving.

Animals↗

PubMed1990

Two-stage model of visual pattern discrimination learning in macaque monkeys (Macaca mulatta and Macaca fuscata).

To investigate the nature underlying the process of pattern discrimination learning, a series of seven experiments on seven working assumptions were undertaken. The main findings are as follows. The pattern discrimination learning consists of two time-dependent stages: The initial or first learning stage is the period of performance at chance, and the succeeding or second stage is the period of performance from just above the chance to a criterion level. The duration of the first stage is dependent on the degrees of cue-response separations, whereas that of the second stage is independent of. During the first stage, monkeys do not attend to the discriminative cue even at small cue-response separations, whereas during the second stage, they achieve pattern discrimination, or pattern perception and cognition, regardless of cue-response separations. After having learned the first pattern task with a cue-response separation, they learned new pattern tasks by means of the second stage, showing marked saving of the duration of the first stage. The findings in the present studies indicate that the first stage of learning is predominantly involved in the process of attending to the discriminative cues remote from the response site (a selective attention to the cue), whereas the second stage is concerned with the process of perception and cognition of the discriminative cue.

Animals↗

PubMed1996

Prenatal exposure to cocaine disrupts discrimination learning in adult rabbits.

Previous studies had shown that intrauterine exposure to cocaine produces an increase in the number of immunoreactive GABA neurons and abnormal dendritic structure of pyramidal cells in the anterior cingulate cortex, a brain region known to be involved in attentional processes and discrimination learning. Because structural abnormalities might be expected to produce related functional deficits, we examined whether intrauterine exposure to cocaine would affect discrimination learning in adult rabbits. We previously reported that cocaine progeny undergoing concurrent acquisition to visual and auditory CSs show a normal rate of learning to a light CS and an accelerated rate of learning to a tone. Here, we report that adult, Dutch-belted rabbits exposed to cocaine in utero showed impaired discrimination learning when responding to a positive visual cue but not when responding to a positive auditory cue. The nature of the deficit consisted of an impaired ability to acquire learned responses to the visual CS+ rather than in an impaired ability to withhold responses to the auditory CS-. Given that auditory stimuli tend to be more salient than visual stimuli in the normal rabbit, the preceding pattern of results suggests that intrauterine cocaine exposure affected the ability to preferentially attend to less salient but relevant stimuli and to ignore more salient, irrelevant stimuli. More importantly, these results indicate that prenatal exposure to cocaine produces neurobehavioral abnormalities which persist into adult life.

Animals↗

PubMed1997

Development of vicarious trial-and-error behavior in odor discrimination learning in the rat: relation to hippocampal function?

Previous work from our laboratory has suggested that hippocampal electrolytic lesions result in a deficit in simultaneous, black-white discrimination learning and reduce the frequency of vicarious trial-and-error (VTE) at a choice-point. VTE is a term Tolman used to describe the rat's conflict-like behavior, moving its head from one stimulus to the other at a choice point, and has been proposed as a major nonspatial feature of hippocampal function in both visual and olfactory discrimination learning. Simultaneous odor discrimination and VTE behavior were examined at three different ages. The results were that 16-day-old pups made fewer VTEs and learned much more slowly than 30- and 60-day-olds, a finding in accord with levels of hippocampal maturity in the rat.

Aging↗

PubMed1985

Visual discrimination learning and interhemispheric transfer in the cat, as affected by 6-hydroxydopamine.

Learning and interhemispheric transfer of visual flux, pattern and form discriminations were studied in the cat after selected exposure of one suprasylvian cortex to 6-hydroxydopamine (6-OHDA). Biochemical assay using High Performance Liquid Chromatography (HPLC) two weeks after 6-OHDA revealed no discernible norepinephrine or dopamine in the treated cortex, but elevated concentrations of these transmitters in the cortex of the opposite hemisphere. Visual discriminations learned before treatment with 6-OHDA were retained at a high level using either the eye on the side of chemical lesion or the eye on the untreated side. An asymmetric deficit in learning new form discriminations was present, however, when the eye on the untreated side was used, in contrast to normal learning using the eye on the side of the hemisphere with depleted adrenergic nerve supply. Once learning was achieved using the lesioned hemisphere transfer of the engram was found to the untreated hemisphere. Thus, the unlesioned hemisphere was unable to learn normally using direct retinal input from the ipsilateral eye, but showed good capacity for learning using indirect visual input from the contralateral eye. This suggests a powerful influence of the callosum on the learning abilities of the two hemispheres, an influence proved by sectioning the callosum. Callosotomy resulted in a reversal of the discriminative capacities seen after 6-OHDA, i.e. the lesioned hemisphere was defective relative to the unlesioned hemisphere.

Animals↗

PubMed1977

Technique for assessing visual discrimination learning in mice.

An automated technique for the study of visual discrimination learning in mice has been developed. The technique utilizes a nose-poke as the operant response. The nose-poke response requires no shaping, has a relatively high operant level and can be used to measure preacquisition exploratory behavior. CD-1 mice acquired a simultaneous brightness discrimination readily but a successive brightness discrimination proved more difficult. A 20 sec intertrial interval was optimal for acquisition of the simultaneous discrimination. Reversal learning was slow. This procedure should prove useful in the study of the effects of pharmacologic and toxic agents on learning and performance in both weanlings and adult mice.

Animals↗

PubMed2004

Neural cell adhesion molecule (NCAM) null mice do not show a deficit in odour discrimination learning.

Polysialylated neural cell adhesion molecule (PSA-NCAM) is predominantly expressed during development where it regulates biological functions including axon targeting and neuronal precursor cell migration. Although dramatically down regulated after birth in most regions of the nervous system, PSA-NCAM remains highly expressed into adulthood in areas that have ongoing regeneration and plasticity such as in the olfactory bulb and hippocampus. Consequently, lack of PSA-NCAM in NCAM null mice results in distinct morphological changes to these areas. The functional correlates of these changes are not well defined although there have been reports that learning is impaired in NCAM null mice. In the present study, we assessed the ability of old and young NCAM null mice to learn an odour discrimination task. We tested male and female experimental and control animals of two different ages: 30-60 days and 12-15 months. During 4 days of training, NCAM null and C57BL/6J received trials where one odour (CS+) was paired with sugar while another odour (CS-) was not. In a subsequent preference test, conducted in the absence of sugar, all animals, regardless of strain or age, spent significantly more time digging in the CS+ odour than in the CS- odour. In addition, there was no significant difference in digging behaviour in the CS+ between the NCAM null and the control animals. These data indicate that deletion of the NCAM gene may change the morphology of the olfactory bulb but does not interfere with the ability to learn an odour discrimination task.

Age Factors↗

PubMed1991

Attentional aspects of classroom behavior and discrimination learning.

Teachers' ratings of their mentally handicapped pupils' classroom behavior were examined as correlates of the child's performance on a discrimination learning task. Teachers completed the 23-item version of the Attention/Distraction Inhibition/Excitation Classroom Assessment Scale (ADIECAS) for a total of 77 pupils. Factors identified as attention/distractibility and responsivity to consequences correlated significantly with number of errors and number of trials to criterion during acquisition of a simultaneous visual discrimination. Attention/distractibility scores also correlated significantly with number of dimensions "attended to" during discrimination learning.

Adolescent↗

PubMed1984

Facilitating visual discrimination learning of moderately and severely mentally retarded children through illumination of stimuli.

The effectiveness of illuminating the positive stimulus after a correct response in visual discrimination training of moderately and severely mentally retarded children was investigated. An economical unit for illumination of stimuli was designed for purposes of the present investigation and for possible use in nonspeech communication training of mentally retarded children. In Experiment 1, the illumination of black stimuli on white backgrounds failed to facilitate discrimination learning. In Experiment 2, however, illumination of white stimuli on black backgrounds facilitated discrimination learning. The findings in the second experiment support the use of changes in illumination as an attention-influencing feature of nonspeech communication keyboards for retarded children.

Attention↗

PubMed2005

Endogenous fluorescence imaging of somatosensory cortical activities after discrimination learning in rats.

Aerobic energy metabolism in the brain is reflected as changes in the green fluorescence of mitochondrial flavoproteins, and the activity-dependent changes in endogenous fluorescence are applicable for functional brain imaging. To understand the roles of cortical plasticity in discrimination learning, we used flavoprotein fluorescence imaging to visualize changes of neural activities in the rat primary somatosensory cortex (SI) after learning. Rats were trained to discriminate floor vibration at rewarded and unrewarded frequencies. After this discrimination learning was accomplished in 3-5 days, the rats were anesthetized with urethane (1.5 g/kg, i.p.), and neural responses were recorded in SI during flutter stimuli applied to the contralateral hindpaw. The fluorescence responses to the stimuli at unrewarded frequencies were selectively depressed in the trained rats, which had behaviorally neglected unrewarded stimuli. The depression of cortical responses was not observed in the rats trained with rewarded stimuli only. Therefore, the stimulus-specific depression in SI might explain a part of neural mechanisms underlying discrimination behavior. To reproduce the stimulus-specific depression of cortical responses in anesthetized rats, tetanic cortical stimulation was paired with flutter stimulation applied to the hindpaw. Selective depression of fluorescence responses or field potentials in SI was induced by the paired stimulation. Our findings suggest that some intracortical circuits in SI are specifically tuned to and modulated by unrewarded stimuli of a particular frequency while SI neurons are responsive to both of rewarded and unrewarded stimuli. The present results indicate the usefulness of flavoprotein fluorescence imaging for investigating somatosensory cortical plasticity after learning.

Animals↗

PubMed1982

Eye movements of monkeys during discrimination learning: role of visual scanning.

Four experiments were conducted on stumptailed monkeys (Macaca arctoides) to determine whether the high levels of visual scanning (shifts in fixation from one discriminative stimulus to the other) seen during discrimination learning play a necessary role in this learning. In Experiments 1 and 2, the monkeys were given a series of two-choice, dot-pattern discrimination reversal problems. Normal visual scanning before a choice response was allowed during all but the reversal trials of half of the problems. On these latter trials, the discriminative stimuli were replaced by an uninformative stimulus after the animals made more than one visual fixation on each discriminative stimulus. Thus, on these trials, the animals were limited, in terms of the information received, to the empirically determined minimum number of scans necessary to maintain high levels of performance on such problems. In both experiments, which differed primarily in the number and type of uninformative stimuli used, the rate of reversal learning was markedly retarded by the experimental condition, with the effect persisting over a long series of problems. The magnitude of the effect was unrelated to the similarity of the uninformative stimulus to the discriminative stimuli. In Experiment 3, the monkeys were given a series of discrimination problems without reversals, during half of which the experimental condition was in effect. The results were similar to those of the first two experiments. Experiment 4 was similar to the preceding experiment except that, under the experimental condition, each trial began with the uninformative stimuli, which were replaced by the discriminative stimuli when visual scanning occurred. The uninformative stimuli had no clear-cut effect on discrimination learning in this experiment. These experiments indicate that the information provided by above-minimum levels of scanning is not necessary for discrimination learning per se, but it dose appear necessary for efficient discrimination learning.

Animals↗

PubMed1975

Genetic analysis of water maze discrimination learning for Mus musculus: polygenes and albinism.

Recombinant inbred strains, their progenitor strains and reciprocal F1 hybrids were given thirty spatial discrimination learning trials in the water maze. The pattern of RI strains in relation to the reciprocal F1 hybrids and the progenitor strains, and differences among strains, suggested that different sets of genes affect the various components of water maze discrimination learning. There was no evidence that the albino gene influenced either inferior or superior performance. Pigmented strains performed as well as, or better than, some albino strains, and albino strain BALB/cBy differed significantly from albino strains CXBG and CXBI. The two reciprocal F1 hybrids differed from blocks 2 and 3 of discrimination trials when swimming time was used a dependent variable. Thus, it appears that performance of the F1 hybrids was influenced by paternal effects, maternal effects, or paternal maternal interactions.

Albinism↗

PubMed1976

Differences in the effects of post-trial chlorpromazine, reserpine, and amphetamine on discrimination learning in rats.

Rats were trained to perform in discrimination learning reinforced by water for 6 days, and were intraperitoneally injected with chlorpromazine, reserpine, or d-amphetamine after each training session. Although chlorpromazine at the dose levels of 0.5 mg/kg or more injected immediately after training impaired learning, the drug did not affect learning when it was injected 60 min after training. Reserpine and amphetamine also impaired learning, but delaying the time intervals between training and injection to 60 min or more had no influence on this learning impairment. Post-trial chlorpromazine and amphetamine had no effect on, but reserpine decreased, motility in the subsequent training session. Chlorpromazine had no effect on water intake in the subsequent session, but reserpine and amphetamine decreased water intake at the dose levels that impaired learning. It was concluded that all three drugs impaired learning, but differed in their effects on learning; chlorpromazine impaired learning by a specific effect on learning itself; reserpine, by a non-specific effect on behavior due to a long acting sedation; and amphetamine, by an effect to decrease the motivation to drink water. The specific effect of chlorpromazine could be related to the hypothesis of "memory trace" synthesis.

Animals↗

PubMed1993

Effects of gestational undernutrition, stress and diazepam treatment on spatial discrimination learning and retention in young rats.

Effects of prenatal undernutrition, stress and diazepam treatment on learning acquisition, and subsequent retention of a spatial discrimination task was assessed in the offsprings. Undernutrition of the dams was induced by restricting food intake to half, throughout the period of gestation, whereas footshock stress and diazepam (0.5 mg/kg, ip) treatment was given from day 13 to 20 of gestation, this being the critical period for neural development in this species. The pups born were subjected to spatial discrimination learning, and retention of the learning acquisition after an interval of one week, in a single unit black/white T-maze, at 8-9 weeks of age. The results indicate that prenatal undernutrition induces significant learning and retention deficits in the offspring, whereas the effect of prenatal stress was limited to only deficit in learning acquisition. Prenatally administered diazepam induced significant deficits in learning acquisition and subsequent retention of the discrimination task in pups culled from normally nourished dams. However, offsprings from diazepam administered undernourished dams exhibited less marked cognitive deficits, which may be attributable to the altered emotional reactivity of pups born to undernourished mothers. Prenatally administered diazepam also induced differential effects in stressed and non-stressed dam offsprings, though the effects were statistically insignificant. The results suggest that prenatal insults, in the form of undernourishment, stress and anxiolytic drugs, leave a lasting imprint on cognitive behaviour of the offspring. The final effect on this behaviour may be determined by the co-existence of these prenatal factors, particularly at a time when the foetus is vulnerable because of neural development and differentiation.

Animals↗

PubMed1994

Effect of gestational undernutrition and chlordiazepoxide treatment on black/white discrimination learning and retention in young rats.

Effects of prenatal undernutrition and chlordiazepoxide treatment on learning acquisition, and subsequent retention, of a black/white discrimination task, was assessed in the offspring. Undernutrition of the dams was induced by restricting food intake to half, throughout the period of gestation, whereas chlordiazepoxide (2.5 mg/kg, ip) treatment was given from day 13 to 20 of gestation, this being the critical period for neural development in this species. The pups born were subjected to brightness discrimination learning, and retention of the learning acquisition after an interval of one week, in a single unit black/white T-maze, at 8-9 weeks of age. The results indicate that prenatal undernutrition induces significant learning and retention deficits in the offspring. Prenatally administered chlordiazepoxide induced significant deficits in learning acquisition and subsequent retention of the discrimination problem. Chlordiazepoxide induced similar learning and retention deficits in the normal and undernourished rats, and exaggerated the learning and retention deficits induced by undernutrition. The results indicated that the prenatal insults in the form of undernourishment and anxiolytic benzodiazepine compounds, leave a lasting imprint on cognitive behaviour of the offspring.

Animals↗