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PubMed1976

Effects of caffeine on discrimination learning, consolidation, and learned behavior in mice.

Three sets of experiments were carried out in a Y water maze in which mice had to swim toward the light or the dark, in two different procedures. The first procedure involved, orientation toward a light source (L procedure), corresponding to natural preference, the latter involved orientation toward the dark (D procedure), corresponding to the acquisition of a new pattern of behavior. In pretrial drug treatments caffeine was administered to two groups of naive mice, tested under one of two experimental conditions. Posttrial drug treatments were made in animals learning the D procedure. Pretrained mice in the L or D procedure were finally injected with increasing doses of the drug. The results show that caffeine administration to naive animals was followed, in the D procedure, by a facilitation of learning and consolidation processes, and in the L procedure by improvements of the natural tendencies. Behavioral disruption followed treatment with the drug in mice pretrained in the D procedure, while only very high doses caused disruption in mice pretrained in the L procedure.

Animals↗

PubMed1999

Neural encoding in orbitofrontal cortex and basolateral amygdala during olfactory discrimination learning.

Orbitofrontal cortex (OFC) is part of a network of structures involved in adaptive behavior and decision making. Interconnections between OFC and basolateral amygdala (ABL) may be critical for encoding the motivational significance of stimuli used to guide behavior. Indeed, much research indicates that neurons in OFC and ABL fire selectively to cues based on their associative significance. In the current study recordings were made in each region within a behavioral paradigm that allowed comparison of the development of associative encoding over the course of learning. In each recording session, rats were presented with novel odors that were informative about the outcome of making a response and had to learn to withhold a response after sampling an odor that signaled a negative outcome. In some cases, reversal training was performed in the same session as the initial learning. Ninety-six of the 328 neurons recorded in OFC and 60 of the 229 neurons recorded in ABL exhibited selective activity during evaluation of the odor cues after learning had occurred. A substantial proportion of those neurons in ABL developed selective activity very early in training, and many reversed selectivity rapidly after reversal. In contrast, those neurons in OFC rarely exhibited selective activity during odor evaluation before the rats reached the criterion for learning, and far fewer reversed selectivity after reversal. The findings support a model in which ABL encodes the motivational significance of cues and OFC uses this information in the selection and execution of an appropriate behavioral strategy.

Action Potentials↗

PubMed1998

An automated training device for pattern discrimination learning of group-housed gerbils.

The setup, designed for the rodent Meriones unguiculatus (gerbil), allows flexible stimulus presentations and rewarding as well as on-line data registration. It consists of a spacious housing where the animals have free access to water. Food is supplied exclusively in the y-maze training compartment and serves as a reinforcer in an operant conditioning paradigm.

Animals↗

PubMed1979

Effects of the lateral septum and latent inhibition on successive discrimination learning.

Damage to the lateral nucleus of the septum in the rat resulted in atypical learning to a previously meaningless stimulus. Nonreinforced preexposure to a stimulus normally makes more difficult subsequent use of that stimulus for learning. The effect of this preexposure on learning is termed latent inhibition and was demonstrated in sham operated animals. Rats in which the lateral septum was damaged demonstrated a paradoxically smaller learning deficit in the presence of a conditioned stimulus that was previously presented without reinforcement, when compared to the performance of both septal lesioned rats no receiving nonreinforced preexposure and sham operates receiving preexposure. The interaction of nonreinforced preexposure and lateral septal lesions can be explained using a proposed sensitization hypothesis.

Animals↗

PubMed1990

Discrimination learning alters the distribution of protein kinase C in the hippocampus of rats.

Protein kinase C (PKC), an enzyme that plays an essential role in eukaryotic cell regulation (Nishizuka, 1988; Huang et al., 1989), is critical to memory storage processes both in the marine snail Hermissenda crassicornis and in the rabbit (Alkon et al., 1988; Bank et al., 1988; Olds et al., 1989). Specifically, activation of PKC mimics neurobiological correlates of classical conditioning in both Hermissenda and the rabbit, and the distribution of the enzyme within the rabbit hippocampus changes after Pavlovian conditioning. Here, we report that the amount of PKC, as assayed by specific binding of 3H-phorbol-12,13-dibutyrate (3H-PDBU), decreased significantly within the hippocampal CA3 cell region in rats trained to solve a water maze task either by cognitive mapping or by visual discrimination strategies, but not in control rats. Furthermore, hippocampal lesions interfered with acquisition of both of these tasks. We interpret these findings to support the conclusion that distributional changes of PKC within the mammalian hippocampus play a crucial role in memory storage processes.

Animals↗

PubMed1996

Spatial and visual discrimination learning in CD1 mice: partial analogy between the effect of lesions to the hippocampus and the amygdala.

CD1 mice with dorsal hippocampal and central amygdaloid lesions were submitted to three radial eight-arm maze tasks requiring various degrees of spatial and nonspatial information processing. The results show that, on the standard version of the radial maze, only hippocampal lesions disrupted performance. In the spatial four-baited path task, both hippocampal and amygdaloid lesions increased the errors and modified the patterns of arm choice. Finally, on the visually cued four-baited path task, the two lesions did not affect any quantitative aspect of performance but a strong and unexpected effect of amygdaloid lesions on the patterns of arm choice was found. Taken together, the results indicate i) an effect of hippocampal lesions in all situations that require performing a spatial discrimination, and ii) an effect of amygdaloid lesions in all situations that require distinguishing between baited and unbaited arms, whatever the modality--spatial or visual--being relevant for discriminating the two sets of arms. The analogy between the effects of hippocampal and amygdaloid lesions specifically observed in the spatial four-baited path task suggests that these two limbic areas can exert a similar control on performance in tasks involving mapping operations based upon the discrimination of rewarded and nonrewarded reinforced locations.

Amygdala↗

PubMed1999

Temporal discrimination learning in severe amnesic patients reveals an alteration in the timing of eyeblink conditioned responses.

This study investigated whether the hippocampal system plays a modulatory role in the timing of conditioned responses (CRs) in eyeblink classical conditioning. Seven bitemporal amnesic patients and 7 controls were randomly presented 2 tone conditioned stimuli (CSs) that were individually paired with two different interstimulus intervals (ISIs) in a delay conditioning task. It was found that amnesic patients' CRs occurred significantly earlier than control participants' CRs at the longer ISI. Amnesic patients also produced significantly more nonadaptive CRs than did control participants, their level of acquisition was less than that of control participants after equating for ISI, and they did not show extinction with the longer ISI. These data suggest a role of the hippocampal system in controlling the precise timing of conditioned eyeblink responses and in acquiring and extinguishing responses within the context of a temporal discrimination task.

Adult↗

PubMed2005

Effects of nitric oxide synthase inhibition on spatial discrimination learning and central DA2 and mACh receptors.

Cholinergic and dopaminergic systems are involved in spatial memory and are modulated by nitric oxide (NO); NO has well documented effects on place learning in rodents. The aim of the present study was to investigate the effect of NOS inhibition on place learning in the water maze and to evaluate the relationships between NOS inhibition, learning performance, dopamine (DA) D2 and muscarinic acetylcholine (mACh) receptors. Male Sprague-Dawley rats received the NOS inhibitor Nomega-Nitro-l-Arginine (l-NA), or saline and were trained in the water maze. Rats that were not trained, but received the same treatments were also included. Following treatments with or without water maze training, [3H]-QNB and [3H]-spiperone binding in cortex, striatum and hippocampus were determined to assess the effects of NOS inhibition and/or learning on DA D2 and mACh receptor regulation. The overall results of the present study showed that: (1) NOS inhibition impairs performance in the MWM; (2) NOS inhibition does not affect specific binding to DA D2 (striatum and hippocampus) and mACh (cortex and hippocampus) receptors; (3) MWM training lowers D2 and mACh receptor binding in cortical regions.

Animals↗

PubMed1979

Discrimination learning of delinquent boys as a function of reinforcement contingency and delinquent subtype.

Previous research has demonstrated the effectiveness of contingency management as a means of behavioral resocialization with delinquent boys on an individual basis. The present study was designed to examine and clarify systematically verbal and token reward and/or punishment. The principal findings of the study were: (1) Neurotic subjects performed at the highest level for punishment, at the lowest level for reward, and at an intermediate level for a combination of reward and punishment, regardless of verbal or token contingency modality. (2) Psychopathic subjects performed best for the joint verbal reward and punishment contingency, but they did not learn over trials for the joint token reward and punishment contingency. Their performance was undifferentiated at asymptote under the separate verbal and token reward or punishment contingencies. (3) Neurotic subjects performed at a significantly higher level than did psychopathic subjects for verbal and token punishment, while psychopathic subjects performed at a significantly higher level than neurotic subjects for verbal and token reward.

Adolescent↗

PubMed1986

Discrimination learning and reversal following electrolytic lesions of the median raphe nucleus.

The current study examined the effects of electrolytic median raphe lesions on the performance of several T-maze discrimination tasks. Raphe lesions were found to impair the reversal, but not the acquisition, of a learned position habit, but to be without effect on either the acquisition or reversal of simultaneous brightness discrimination task. Rats with raphe damage were severely impaired in the acquisition of either a successive brightness discrimination task or of a delayed spatial alternation task. These results are similar to those which have been reported after limbic damage, and support the view that the paramedian midbrain tegmentum may play an important role in the functioning of limbic structures.

Animals↗

PubMed1994

Reinforcement effects of Boschniakia rossica on discrimination learning in cholinergic lesions of rats.

The dried herb or stem of Boschniakia rossica (Boschniakiae Herba) has been used as an antisenile agent in the Jilin Province of China. To elucidate the effects of Boschniakiae Herba on decreased learning ability and memory weakness, a 50% ethanol extract of Boschniakiae Herba was administered to rats whose nucleus basalis of Meynert had been destroyed by the injection of ibotenic acid. This administration showed a significant improvement in the decrease of the ratio of correct responses caused by destruction of the nucleus basalis of Meynert. These results suggest that B. rossica would be therapeutic in senility.

Animals↗

PubMed1991

A water-maze discrimination learning deficit in the rat following lesion of the habenula.

Although the habenula occupies a potentially important link between forebrain and midbrain, lesion of the complex produces little effect in most standard behavioral paradigms. More recently, it has been shown that such lesions may impair the ability to initiate or switch responses appropriate to environmental contingencies but only under demanding conditions. Although such deficits have been described as response failures, they could equally well be attributed to restricted attentional mechanisms. The present study was designed to further substantiate a role for the habenula in acquisition of adaptive behavior under demanding conditions and to examine the possible contribution of attentional failure. The initial response preference to 'escape' onto platforms situated in two chambers at the distal end of a water tank was established for groups of lesioned and sham-operated rats. Rats were subsequently trained in discrete trials to escape by choosing the side of the nonpreferred chamber. During training the choice of escape chamber was cued by distracting black or white visual stimuli displayed on the tank sides and above the entrances to the chamber. These were moved over trials so as to be nonpredictive of the appropriate escape position. Lesioned animals were significantly impaired in the acquisition of this positional discrimination. Analysis of response times suggested that both lesion and control animals were attending to the irrelevant visual cue. The results confirm a behavioral inflexibility following lesion of the habenula and suggest that this deficit cannot be explained simply in terms of a failure to attend to environmental cues. The lesion deficit also could not be attributed to a response perseveration.

Animals↗

PubMed2000

Effects of the size of the morris water tank on spatial discrimination learning in the CFW1 mouse.

The spatial orientation of mice and rats in tasks such as the Morris water escape task is guided by extramaze cues. Using data from the control groups of mice used in two drug-finding experiments, we addressed the question whether the size of the Morris water tank affects spatial learning in mice. In these experiments, CFW1 mice had been tested in either a small or a large water tank. Reanalysis of the data revealed that pool size did not affect learning or bias for the previous training quadrant. The Morris water escape task appears to act as a severe stressor in particular mouse strains, and a high stress level may interfere with the learning ability or performance of mice, which may have serious consequences for the interpretation of data. This is of special relevance when assessing the Morris maze performance of strains of mice with a different sensitivity to stress. We conclude that mice can best be tested in a small pool, because the time and distance swam to find and escape onto the platform is decreased and the probability of success (that is, of encountering the platform) is increased. This will reduce stress and hence increase the comparability of data between different strains of mice.

Animals↗

PubMed2005

Auditory frequency discrimination learning is affected by stimulus variability.

We explored the effects of training set variability on learning and generalization of pure-tone frequency discrimination (FD) in three groups of untrained, normally hearing adult listeners. Group 1 trained using a fixed standard tone at 1 kHz (fixed), Group 2 on slightly varying (roving) tones around 1 kHz, and Group 3 on widely varying standard frequencies (wide-roving). Initially, two thirds of all listeners had low FD thresholds (good listeners) and one third had intermediate to high thresholds (poor listeners). For good listeners, slight variations in the training set slowed learning but wide variations did not. Transfer to untrained frequencies (up to 4 kHz) and to the fixed condition was equivalent regardless of training condition, but Group 1 listeners did not fully transfer learning to the roving condition. For poor listeners, any variation in the training condition slowed learning and impaired transfer to other frequencies but did not affect transfer to untrained conditions. Thus, the effects of training set on progress and outcome depend on set variability and individual FD ability.

Adult↗

PubMed1975

Extinction by retarded children following discrimination learning with and without errors.

Four groups of retarded children (N = 4 in each group) were trained to respond to a triangle with apex up (S+) and not to a triangle with apex down (S-), with and without errors. A free-operant procedure in which responding to S+ was intermittently reinforced and a trial procedure in which all responses to S+ were reinforced were compared. An extinction procedure in which responses were no longer reinforced was then introduced. Extinction resulted in substantial responding during S- for all groups, except the free-operant errorless group. S- responding during extinction did not differ between the errorless and error-trial groups and was maximum for the free-operant error group.

Achievement↗

PubMed1975

Role of cortex in Pavlovian discrimination learning.

Two totally neodecorticate rabbits and two groups of normal rabbits were trained on a light-tone differentiation using a Pavlovian nictitating membrane response. The significance of the two stimuli involved in the differentiation was then reversed. Excellent initial differentiations were produced by both decorticates and normals, although there was some evidence of a small retardation of conditional response acquisition in the decorticates in this first stage of the experiment. Under reversal conditions the decorticates extinguished responding to the formerly positive conditional stimulus in fewer trials and produced more complete differentiation performances than normal animals. The decorticates, unlike the normal animals, failed to show a reduction in conditional response onset latencies during either differentiation or reversal training.

Acoustic Stimulation↗

PubMed2003

Acquired equivalence and distinctiveness in human discrimination learning: evidence for associative mediation.

In the first stage of Experiments 1-3, subjects learned to associate different geometrical figures with colors or with verbal labels. Performance in Stage 2, in which the figures signaled which of 2 motor responses should be performed, was superior in subjects required to make the same response to figures that had shared the same Stage 1 associate. A third stage of testing showed that the events used as associates in Stage 1 were capable of evoking the motor response trained in Stage 2, an outcome predicted by an associative interpretation of such transfer effects. Experiment 4 provided evidence that the relevant associations can be effective in controlling motor responding even when subjects report an antagonistic relationship between events.

Adolescent↗

PubMed1980

Differential effects of inescapable shock on escape performance and discrimination learning in a water escape task.

The effects of inescapable shock on subsequent T-maze water escape and position discrimination performance were evaluated in seven experiments. Escapable shock did not disrupt water escape performance; however, escape performance was retarded 24 hr after inescapable shock. These deficits were not apparent if escape was possible upon stress inception; however, pronounced deficits were noted if sustained active responding was necessitated by briefly (3-5 sec) preventing escape. When water escape testing was conducted in relatively warm water (20 degrees C), the disruptive effects of preshock were not apparent. In colder water (15 degrees C), which increases the motor difficulty of the task, the disruptive effects of preshock were noted. When the motor difficulty of the task was increased further, by testing mice in 10 degrees C water, or when the associative difficulty was increased by using a vigorous reversal learning task, the differences between the preshocked and nonpreshocked groups were obviated. Exposure to inescapable shock did not disrupt position discrimination performance regardless of the motor difficulties of the task. Similarly, deficits of discrimination performance were not apparant in mice exposed to inescapable shock even when the associative difficulty of the task was increased by removing intramaze cues or by testing animals in a position discrimination reversal task. It is concluded that inescapable shock results in deficits of response maintenance but probably has a minor, if any, influence on cognitive/associative processes.

Animals↗