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PubMed1994

The nature and processes of preverbal learning: implications from nine-month-old infants' discrimination problem solving.

Nine-month-old infants' performance on discrimination-learning problems was investigated in four experiments using the synchronous reinforcement paradigm. These experiments were organized around basic theoretical postulates concerning the relation between attention and learning. In each of the experiments, infants were trained to respond differentially to a particular stimulus feature, with the goal of establishing whether they could learn to respond to a particular stimulus feature under conditions where other stimulus dimensions were present and varying. In the first experiment, 48 infants were trained to fixate visually on a particular feature in a pair of stimuli that varied in color, form, and position dimensions. Contingencies for responding were then shifted either within a dimension (reversal shift) or across dimensions (nonreversal shift). Infants learned to respond to the reinforced feature during initial training; moreover, infants assigned to a reversal shift condition showed a higher level of transfer of learning during the test phase than those assigned to a nonreversal shift condition. The second experiment extended the results of Experiment 1 by testing 48 additional infants under conditions in which the number of varying irrelevant dimensions was increased during the shift phase. Although the difficulty added to this task by this manipulation made transfer more difficult for all infants, results again indicated that transfer of learning was more evident for infants in a reversal shift than a nonreversal shift condition. In the third experiment, 64 infants were trained in a similar manner, except that completely new values were substituted during shift phases on the color and form dimensions. This manipulation was meant to probe whether infants were formulating a dimension response from previous training and to test the predictions of such dimension processing for transfer of learning to a functionally new problem. Infants were reinforced for fixating on a new feature either within the same dimension as during training (intradimension shift) or within the dimension that was not originally trained (extradimension shift). Transfer of learning was clearly superior in the intradimension shift condition. The findings of the first three experiments suggested that, during discrimination-learning problems, infants selected and tested individual stimulus features and dimensions from an array of potential solutions to the problem until discovering the one that was consistently associated with reinforcement.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1996

Expression of the transcription factor Zif268 in the temporal cortex of monkeys during visual paired associate learning.

In humans and monkeys, memory consists of various components which were initially revealed through neuropsychological studies of amnesic patients. One memory component, the long-term memory about facts and events (declarative memory), has been shown to require the integrity of the medial temporal lobe and the neocortex. To investigate a map of gene expression during declarative memory formation in the primate, we monitored expression of immediate early genes in the temporal lobe of macaque monkeys. We trained the monkeys to learn visual associative memory tasks, and immunohistochemically analysed the expression of protein products of immediate early genes. We found that Zif268, a transcription factor regulated by neuronal activity, accumulated in patches in the anterior temporal lobe during visual stimulus-stimulus association learning, whereas other transcription factors, c-Fos and JunD, were not. By contrast, the patchy expression of Zif268 was not observed during another type of learning, visual discrimination learning. These results suggest that Zif268 activates a gene cascade related to the formation of long-term memory in the primate.

Animals↗
PubMedDate not supplied

Human temporal behavior and discrimination-reversal learning.

The present study demonstrates that a relationship exists between individual differences in temporal behavior and individual differences in human discrimination-reversal learning behavior. When the results of performance on a time-estimation task employing the method of reproduction are compared with the results of acquisition performance on a complex form of discrimination-reversal learning task is can be demonstrated that underestimation of time is associated with faster learning and overestimation of time is associated with slower learning of the discrimination task. The experimental design was based on the historical fact that the Sechenov-Pavlov and Spence-Hull formulations assigned a primary role in learning to excitation and inhibition as intervening variables between the input of stimulation and output of response. The present study also used the tasks of time estimation and discrimination learning as dependent variables; and the concept that underestimation of time is associated with and underlying predominance of excitatory processes as a hypothetical construct. The conclusion was reached that one of the many theoretical processes which may be used to explain discrimination learning is the concept that acquisition of the correct response may be viewed as a function of the individual rates at which excitatory processes come to be conditioned to a predominance over existing inhibitory processes.

Adult↗
PubMed2001

Medial geniculate, amygdalar and cingulate cortical training-induced neuronal activity during discriminative avoidance learning in rabbits with auditory cortical lesions.

This study addressed the neural mediation of discriminative avoidance learning, wherein rabbits step in a wheel apparatus in response to an acoustic conditional stimulus, the CS+, to avoid a foot shock, and they learn to ignore a different stimulus, the CS-, not followed by foot shock. Previously, muscimol-induced inactivation of the amygdala in the first session of training prevented learning during the inactivation and permanently blocked the development of discriminative training-induced neuronal activity (TIA) in the medial division of the medial geniculate nucleus (MGm). These results suggested that amygdalar neurons induce discriminative TIA in the MGm via basolateral (BL) amygdalar axonal projections to the auditory cortex. To test this hypothesis, the activity of neurons in the MGm was recorded during learning in rabbits with lesions of the auditory cortex. Recordings were also made in the lateral and BL amygdalar nuclei and in the cingulate cortex. In support of the hypothesis, discriminative learning in rabbits with lesions was impaired significantly during early training sessions 1-4; in these same sessions, discriminative TIA was abolished in the MGm, the BL nucleus, and the anterior cingulate cortex. The lesions also blocked posterior cingulate cortical discriminative TIA in training sessions 1-2 but spared TIA in sessions 3-7. Lateral amygdalar neurons showed gradual development of discrimination that was not significantly affected by the lesions. The results demonstrate a critical role of auditory cortex in early discriminative learning and in the production of early discriminative TIA in multiple areas.

Acoustic Stimulation↗
PubMed2002

Learning to discriminate simple sinusoidal gratings is task specific.

Learning transfer effects of a modified spatial frequency discrimination task with simple sinusoidal gratings on various untrained test tasks, testing performance in relative position, local width and global size discrimination, have been investigated. Six subjects were exposed to grating stimuli of varying spatial frequency and size but constant relative position while they had to respond only to spatial frequency. In the course of 7 consecutive days all subjects showed significant reduction of spatial frequency discrimination thresholds. Comparison of discrimination thresholds for the untrained test tasks, taken before and after the learning epoch, reveals complete learning transfer to spatial frequency discrimination with gratings of constant size and variable relative position, but complete lack of transfer when grating spatial frequency is shifted about one octave lower. Further, there is improvement of relative position discrimination and width discrimination of single luminance bars, which is not very specific for the learnt spatial frequency. Although size variation was part of the learning procedure, discrimination of global stimulus size did not improve. Generally, the observed scheme of learning transfer reveals that there is learning only for stimulus attributes that are behaviorally relevant in the learning task. The differential scheme of improvement and code usage in the test tasks strongly indicates involvement of higher stages capable of independent access to different coding domains, as well as attentionally guided attribute selection and suppression. Supported by other recent findings, it is suggested that discrimination learning can be understood as a higher level process of gradual refinement of code selection out of a rich code base provided by lower level stages.

Adult↗
PubMed2006

Learning motion discrimination with suppressed and un-suppressed MT.

Perceptual learning of motion direction discrimination is generally thought to rely on the middle temporal area of the brain (MT/V5). A recent study investigating learning of motion discrimination when MT was psychophysically suppressed found that learning was possible with suppressed MT, but only when the task was sufficiently easy [Lu, H., Qian, N., Liu, Z. (2004). Learning motion discrimination with suppressed MT. Vision Research 44, 1817-1825]. We investigated whether this effect was indeed due to MT suppression or whether it could be explained by task difficulty alone. By comparing learning of motion discrimination when MT was suppressed vs. un-suppressed, at different task difficulties, we found that task difficulty alone could not explain the effects. At the highest difficulty, learning was not possible with suppressed MT, confirming [Lu, H., Qian, N., Liu, Z. (2004). Learning motion discrimination with suppressed MT. Vision Research 44, 1817-1825]. In comparison, learning was possible with un-suppressed MT at the same difficulty level. At the intermediate task difficulty, there was a clear learning disadvantage when MT was suppressed. Only for the easiest level of difficulty, did learning become equally possible for both suppressed and un-suppressed conditions. These findings suggest that MT plays an important role in learning to discriminate relatively fine differences in motion direction.

Discrimination, Psychological↗
PubMed1977

Effect of introducing novel configurational cues on a learned color discrimination in squirrel monkeys.

The study explored the effect of introducing novel cues on a learned color discrimination. 6 squirrel monkeys were initially trained to discriminate between plaques covered with green and brown construction paper. In a series of transfer tests, these color cues were then presented in 6 different patterns and varied in 4 sizes. The results indicate that some patterns will produce more disruption than others. Furthermore, reducing the size of the cues may also lead to a decrement in performance level. The outcome corresponds well with those of studies which show that contextual variables influence the acquisition of discriminative responses.

Animals↗
PubMed2004

Studies of learning and problem solving in two species of Australian marsupials.

This article reviews the authors' recent work with two species of Australian marsupials on several learning and conditioning experiments. The quokka (Setonix brachyurus) is a cat-sized herbivorous wallaby that inhabits offshore islands around south-western Australia. The fat-tailed dunnart (Sminthopsis crassicaudata) is a mouse-sized carnivorous marsupial that inhabits much of inland Australia. Both species were successful in learning simple discriminations, learning sets and reversal sets. Quokkas and dunnarts were also tested on two configural discrimination tasks: transverse patterning and negative patterning; only the dunnarts successfully solved these tasks. Dunnarts were also the only species to show one-trial learning in reversal set training. Dunnarts may be particularly useful subjects in future studies of brain-behavior relationships, since these animals have some interesting neuroanatomical features, demonstrate a wide range of fast learning abilities, and as pouch young, can be accessed during early developmental stages.

Animals↗
PubMed2006

Contextual control in discrimination reversal learning.

In 3 human predictive learning experiments, the authors examined contextual control of responding in discrimination reversal learning. In Phase 1, a discrimination between 2 stimuli (A+, B-) was trained in Context 1. During Phase 2, participants received discrimination reversal training (A-, B+) in Context 2. Testing occurred in Context 1 and Context 2 (Experiments 1A and 1B) or in Context 1 and Context 3 (Experiment 2). During the test phase, performance in Context 1 and Context 2 reflected the contingencies trained during Phase 1 and Phase 2, respectively. When testing occurred in Context 3, there was no discriminative responding between A and B. In addition, the experiments demonstrated that discriminating stimuli with a consistent reinforcement history were also affected by contextual manipulations. Results indicate that each training context acquires the ability to control performance. Unique-cue and configural approaches account for a major part of the results.

Adolescent↗
PubMed1989

Verbalization of appropriate and inappropriate cues in discrimination reversal learning by moderately mentally retarded children.

Effects of verbalization on discrimination reversal learning for moderately mentally retarded children were examined under three training conditions. Predicted results indicated that verbalization of both appropriate and inappropriate cues within relevant dimension significantly facilitated reversal shift performance, as compared to verbalization of only appropriate cues or non-verbalization. Results were interpreted to be due to the fact that verbalization of both appropriate and inappropriate cues actually served to utilize attentional or verbal mediators in terms of combining appropriate with inappropriate cues within relevant stimulus dimension.

Adolescent↗
PubMed1987

Olfaction and the "data" memory system in rats.

A set of studies was conducted to characterize the memory system involved in successive olfactory discrimination learning in rats. Two odors emanated from different arms of a radial maze; one of the arms contained a water reward. After training on four or five pairs of odors (20 trials per day), rats learned to discriminate the members of a new pair in 5-10 trials. Experiments in which either member of the pair was compared with a novel cue indicated that the rats learn both positive and negative odors, rather than simply ignoring the negative cue. The memories for the odors were apparently persistent, and no evidence for retroactive interference from subsequent training was obtained. Training on 30 pairs did not result in any slowing of subsequent learning, which suggest that the capacity of the memory system for odors is substantial. In a second group of experiments, we tested whether rats distinguish between odors by identifying unshared subcomponents or instead treat odors in a gestalt (i.e., unitary) fashion. Animals trained on three component odors with two in common did not recognize the elements that were unshared when these were presented by themselves. Even when one of the two shared components was combined with the differentiating component into a cue (i.e., two thirds of the original three-component odor), the new cue was treated as a novel odor. However, inclusion of a previously learned simple odor in a complex odor did affect the learning of that odor.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2002

Behavioural consequences of nucleus accumbens dopaminergic stimulation and glutamatergic blocking in pigeons.

Upon systemic administration of apomorphine, a potent dopamine agonist, pigeons show a bout of pecking behaviour. When the drug is repeatedly administered a sensitization takes place that is associated with pronounced discrimination learning. Here we show that intra-cerebral injections of apomorphine in the periphery of the nucleus accumbens of pigeons also elicit pecking. We additionally show that injections of 5-amino-phosphonohepatnoic acid, a NMDA-glutamate receptor blocker, into the Acc impairs the performance of a learned visual discrimination incorporating pecking as a choice response. We conclude that, as it is the case in mammals, the control mechanisms of learned sensory-motor behaviour in birds involves dopaminergic and glutamatergic synaptic transmission within the nucleus accumbens area.

Animals↗
PubMedDate not supplied

Re-evaluation of a programmed method to teach generalized identity matching to sample.

Programmed training in identity matching to sample was given to six participants who had severe mental retardation, mental age-equivalent scores of 3.0 years or less, and histories of failures in prior assessments and training attempts with standard procedures. An intermediate goal of the training program was to establish one-trial discrimination learning (OTDL), where new discriminations are acquired after a single training trial, OTDL was included because an analysis of the task requirements for identity matching suggested that it could be a prerequisite skill. One participant was eliminated from the experiment when stimulus control by prompting procedures broke down relatively early in training. Only one of the remaining participants achieved OTDL. When the program was modified to eliminate OTDL as an intermediate goal, for participants completed it and passed tests for generalized identity matching with high accuracy scores. The program was partially successful with the sixth participant in that it established highly accurate and reliable identity matching when different stimuli were displayed on every trial (nonconditional-function matching), but not when the same set of comparison stimuli was displayed on every trial (conditional-function matching). The results showed that (a) one-trial discrimination learning appears to be sufficient but not necessary for identify matching, and (b) the program successfully established identity matching in a majority of difficult-to-teach students who had well-documented failures to learn by standard teaching methods.

Adolescent↗
PubMedDate not supplied

Discrimination reversal conditioning of an eyeblink response is impaired by NMDA receptor blockade.

In the present study we examined the effects of the specific NMDA receptor antagonist CPP on discrimination reversal learning in rabbits. We report two primary findings. First, the institution of NMDA receptor blockade had no effect on a learned discrimination. Second, after stimulus reversal, CPP treatment impaired acquisition of the discrimination reversal. This impairment manifested itself early in training as a retardation in acquisition of a CR to the new CS+ and late in training as an inability to suppress responsiveness to the new CS-. Given the comparability of the present results with previously published results for phenytoin-treated rabbits, we suggest that the effects of phenytoin on learning in this paradigm is at least in part mediated by its effects on NMDA receptors. We further suggest that these findings emphasize the need to better define the role of NMDA receptor activation and hippocampally-mediated circuits in a variety of associative learning paradigms.

Animals↗
PubMed1988

Human amnesia and animal models of amnesia: performance of amnesic patients on tests designed for the monkey.

The performance of amnesic patients was assessed on five tasks, which have figured prominently in the development of animal models of human amnesia in the monkey. The amnesic patients were impaired on four of these tasks (delayed nonmatching to sample, object-reward association, 8-pair concurrent discrimination learning, and an object discrimination task), in correspondence with previous findings for monkeys with bilateral medial temporal or diencephalic lesions. Moreover, performance of the amnesic patients correlated with the ability to verbalize the principle underlying the tasks and with the ability to describe and recognize the stimulus materials. These tasks therefore seem to be sensitive to the memory functions that are affected in human amnesia, and they can provide valid measures of memory impairment in studies with monkeys. For the fifth task (24-hour concurrent discrimination learning), the findings for the amnesic patients did not correspond to previous findings for operated monkeys. Whereas monkeys with medial temporal lesions reportedly learn this task at a normal rate, the amnesic patients were markedly impaired. Monkeys may learn this task differently than humans.

Alcohol Amnestic Disorder↗
PubMed1998

Prenatal cocaine exposure: long-term deficits in learning and motor performance.

We have developed a rabbit model of in utero exposure to intravenous injections of cocaine given twice daily to dams from gestational days 8-29. At the doses employed (4 mg/kg, injected twice daily), no differences were found in the body weight gain of dams, time to delivery, litter size, and body weight or other physical characteristics of the offspring. However, cocaine-exposed pups displayed an abnormal structural and neurochemical development of the anterior cingulate cortex which persisted into adulthood. In agreement with the known functions of the anterior cingulate cortex, we found that adult, sexually mature rabbits, exposed to cocaine prenatally, demonstrate impairments in motor function, alterations in associative learning and severe impairments in discrimination learning. Moreover, the alterations in discrimination learning were interpreted to be due to deficits in attentional processes. Specifically, cocaine progeny preferentially attend to more salient stimuli even when these are not relevant to the task. Consequently they have difficulty in attending to less salient but relevant stimuli when more salient but irrelevant stimuli occur in the same context. We concluded that the learning deficits are a reflection of the morphologic and neurochemical abnormalities of the anterior cingulate cortex. Alterations in dopamine function of the caudate nucleus may also contribute to the deficits in motor performance.

Acoustic Stimulation↗
PubMed1985

Discrimination shift learning and response inhibition of moderately and severely mentally retarded and non-retarded children.

Simple two-choice discrimination shift learning performances of 20 moderately and severely mentally retarded children were compared with those of 20 non-retarded ones. A learning task arranged with a pair of yellow circle and green triangle slides was used. No difference was found between mentally retarded and non-retarded children in the learning rate of initial discrimination, but the mentally retarded attained shift discrimination more slowly than the non-retarded. Also, the extinction of initial positive responses in mentally retarded children was slower than in non-retarded children. It was suggested that the difficulty of discrimination shift in severely subnormal children is due to failure to suppress a previously learned response to prior positive cues.

Adolescent↗