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PubMed1991

Ontological categories guide young children's inductions of word meaning: object terms and substance terms.

Three experiments assessed the possibility, suggested by Quine (1960, 1969) among others, that the ontology underlying natural language is induced in the course of language learning, rather than constraining learning from the beginning. Specifically, we assessed whether the ontological distinction between objects and non-solid substances conditions projection of word meanings prior to the child's mastery of count/mass syntax. Experiments 1 and 2 contrasted unfamiliar objects with unfamiliar substances in a word-learning task. Two-year-old subjects' projection of the novel word to new objects respected the shape and number of the original referent. In contrast, their projection of new words for non-solid substances ignored shape and number. There were no effects of the child's knowledge of count/mass syntax, nor of the syntactic context in which the new word was presented. Experiment 3 revealed that children's natural biases in the absence of naming do not lead to the same pattern of results. We argue that these data militate against Quine's conjecture.

Child, Preschool↗

PubMed2002

Role of the dorsomedial striatum in behavioral flexibility for response and visual cue discrimination learning.

These experiments examined the effects of dorsomedial striatal inactivation on the acquisition of a response and visual cue discrimination task, as well as a shift from a response to a visual cue discrimination, and vice versa. In Experiment 1, rats were tested on the response discrimination task followed by the visual cue discrimination task. In Experiment 2, the testing order was reversed. Infusions of 2% tetracaine did not impair acquisition of the response or visual cue discrimination but impaired performance when shifting from a response to a visual cue discrimination, and vice versa. Analysis of the errors revealed that the deficit was not due to perseveration of the previously learned strategy, but to an inability to maintain the new strategy. These results contrast with findings indicating that prelimbic inactivation impairs behavioral flexibility due to perseveration of a previously learned strategy. Thus, specific circuits in the prefrontal cortex and striatum may interact to enable behavioral flexibility, but each region may contribute to distinct processes that facilitate strategy switching.

Animals↗

PubMed1989

Visual effects of opiates in pigeons: II. Contrast sensitivity to sinewave gratings.

In a simultaneous forced-choice procedure, three pigeons learned to discriminate between a blank field and sinewave gratings of equal space-averaged luminance. Conditions included two spatial frequencies and, for each, a series of contrasts, which were varied over a range sufficient to generate psychometric functions. Drug tests used two doses of morphine and a condition that combined naloxone with the higher dose. Morphine decreased contrast sensitivity, although this outcome was reliable only at the higher dose and the higher spatial frequency. This effect was reduced and usually blocked by naloxone. Morphine-induced changes in pupil size were too small to account for the opiate effect.

Animals↗

PubMed1993

Thalamic radiodensity and cognitive performance in mild and moderate dementia of the Alzheimer type.

Eighteen patients with mild to moderate dementia of the Alzheimer type underwent cranial computed tomography (CT) and tests of visual attention, recognition and learning. Two subgroups emerged. Subgroup 1 was made up of ten patients who showed impaired visual recognition learning and memory, but intact attention in marked contrast to subgroup 2, which was made up of eight patients, in whom all of these functions were impaired. Planimetric and densitometric CT measurements yielded one significant difference between the two subgroups: a decreased radiodensity in the dorsomedial thalamus of the patients from subgroup 2. Lower radiodensity in the right dorsomedial thalamic area was significantly correlated with impaired performance on the test of attentional set shifting, more specifically, with deficits at the reversal learning stage. These results are interpreted in the context of recent evidence linking reversal learning to a neural network comprising the cholinergic basal forebrain, the amygdala and the orbitofrontal cortex, as well as the mediodorsal nucleus, and recent evidence of cholinergic deficits in this structure in patients with Alzheimer's disease.

Aged↗

PubMed1984

The effects of lesions of the habenula nucleus on lever press behaviour during a tandem operant schedule with contrasting response requirements.

The effect of bilateral lesions of the habenula nuclei in male Lister hooded rats was assessed in performance of a well learned complex tandem operant reinforcement schedule. The schedule requirement involved two successive and contrasting components in which 15 operant lever press responses followed by inhibition of the same response for a period of 15 s provided liquid-food reinforcement. Initially little disruption of performance was seen when each component of the schedule was differentially signalled with an external cue. However, relative to controls, lesioned animals showed an increasing disruption of performance when such cues were omitted. The deficit in performance of lesioned animals was not a simple failure to inhibit responding that could be predicted from an altered input from septal areas. It is suggested that these behavioural data are consistent with the anatomical evidence for the habenula as a functional relay for the integration of information from limbic structures and the striatum and that lesions of the habenula affect the ability of animals to maintain effective response strategies, particularly when these are under intrinsic control.

Animals↗

PubMed2000

Parents' and teachers' ratings of problem behaviours in children: genetic and contrast effects.

We obtained ratings on the Conners' scales from teachers (CTRS-28) and parents (CPRS-48) for 61 monozygotic and 64 dizygotic twin pairs, aged between 7 and 11 years. Model-fitting analyses were carried out to estimate the extent of genetic and environmental influences on problem behaviours, and to explore possible contrast effects in ratings by parents and teachers. Confirming previous findings with other measures, there was evidence of moderate to strong genetic effects on a range of problem behaviours. Parents' ratings on the Anxiety, Impulsive-Hyperactive and Learning Problem sub-scales showed significant evidence of contrast effects. There was no evidence of such rater bias or competitive sibling interaction effects in ratings by teachers, or in parents' ratings on the Conduct Problem and Psychosomatic sub-scales.

Analysis of Variance↗

PubMed2000

Role of serotonin in memory impairment.

As a result of its presence in various structures of the central nervous system serotonin (5-HT) plays a role in a great variety of behaviours such as food intake, activity rythms, sexual behaviour and emotional states. Despite this lack of functional specialization, the serotonergic system plays a significant role in learning and memory, in particular by interacting with the cholinergic, glutamatergic, dopaminergic or GABAergic systems. Its action is mediated via specific receptors located in crucial brain structures involved in these functions, primarily the septo-hippocampal complex and the nucleus basalis magnocellularis (NBM)-frontal cortex. Converging evidence suggests that the administration of 5-HT2A/2C or 5-HT4 receptor agonists or 5-HT1A or 5-HT3 and 5-HT1B receptor antagonists prevents memory impairment and facilitates learning in situations involving a high cognitive demand. In contrast, antagonists for 5-HT2A/2C and 5-HT4, or agonists for 5-HT1A or 5-HT3 and 5-HT1B generally have opposite effects. A better understanding of the role played by these and other serotonin receptor subtypes in learning and memory is likely to result from the recent availability of highly specific ligands, such as 5-HT1A, 5-HT1B, 5-HT2A receptor antagonists, and new molecular tools, such as gene knock-out mice, especially inducible mice in which a specific genetic alteration can be restricted both temporally and anatomically.

Aging↗

PubMed1986

Kainate and electrolytic lesions of the lateral habenula: effect on avoidance responses.

Male Sprague Dawley rats (n = 24), which received either bilateral electrolytic lesions, kainic acid lesions or sham treatments in the lateral habenula, were tested for acquisition of a one-way, conditioned avoidance response. Animals with electrolytic lesions failed to learn the avoidance task within 15 trials. In contrast, rats with kainic acid lesions performed as well as the control group. The results indicate that the disruption of the septal-medial habenula-interpenduncular nucleus pathway may be responsible for the observed avoidance deficit in electrolytically lesioned animals.

Animals↗

PubMed1995

Investigation of the devaluation interpretation of anticipatory negative contrast.

Rats suppress intake of an acceptable substance (e.g., 0.15% saccharin) when it is followed by a preferred substance (e.g., 32% sucrose) in once per day pairings. The role of a learned devaluation of the initial solution in suppressed intake (anticipatory negative contrast) was investigated. The findings included the following: (a) Flavors or odors as within-subject cues precluded the occurrence of anticipatory contrast, conditioning flavor and odor preferences instead, which appeared to antagonize suppressed intake. (b) Anticipatory contrast was obtained when within-subject context cues, temporal alternation cues, or drinking-spout cues were used. (c) Preference tests conducted with the spout cues showed that devaluation of the initial substance was not necessary for the occurrence of negative anticipatory contrast.

Animals↗

PubMed2005

The effect of the mGlu5 receptor antagonist MPEP in rodent tests of anxiety and cognition: a comparison.

RATIONALE: Antagonists at the metabotropic glutamate 5 (mGlu5) receptor produce robust anxiolytic effects in a number of rat tests. However, there is evidence that mGlu5 receptor antagonists may also impair working memory and spatial learning following intracerebroventricular administration. OBJECTIVES: The aim of this study is to compare the effect of the potent and selective mGlu5 receptor antagonist, 2-methyl-6-(phenylethynyl)-piperidine (MPEP), administered systemically on rodent tests of cognition and anxiety. METHODS: MPEP was assessed in the following rodent tests, 60 min following oral administration: Geller--Seifter conflict, conditioned emotional response (CER), Vogel conflict, delayed match to position (DMTP) and Morris water maze. Diazepam was also tested as a comparator. RESULTS: MPEP had a significant anxiolytic effect, comparable in magnitude to diazepam, at 10--30 mg/kg in the two conflict and CER tasks. There was no effect of MPEP up to 30 mg/kg on working memory in the DMTP task, but at 100 mg/kg, there was a significant reduction in choice accuracy at the longest delay interval (24 s). MPEP (3--30 mg/kg) did not significantly impair spatial learning in the Morris water maze, although during the last probe trial, 30-mg/kg-treated rats were significantly less accurate than controls. In contrast, diazepam significantly impaired performance in both the DMTP and Morris water maze tests. Assessment of plasma and brain concentration of MPEP approximately 75 min following oral administration showed a dose linearity from 3 to 30 mg/kg and good brain penetration, i.e. a brain/plasma ratio of 3.1. CONCLUSIONS: Oral administration of the selective mGlu5 receptor antagonist MPEP induces a robust anxiolytic-like effect in rat conflict tests comparable to that seen with diazepam, but in contrast to diazepam, MPEP does not impair working memory or spatial learning at anxiolytic doses.

Animals↗

PubMed2004

An introduction to the reading of Bion.

The author suggests that a good deal of the confusion that arises in the course of reading Bion derives from the fact that Bion's analytic writing is comprised of two periods of work that involve markedly different conceptions of psychoanalysis. These two periods require of the reader very different ways of reading and generate contrasting experiences in reading. Bion, in passages in Learning from experience (1962) and Attention and interpretation (1970), offers advice to the reader regarding how he would like his 'early' and 'late' work to be read. The author treats the experience of reading these passages as ports of entry into the fundamental tenets underlying Bion's widely differing conceptions of the psychoanalytic enterprise. The experience of reading early Bion generates a sense of psychoanalysis as a never completed process of clarifying obscurities and obscuring clarifications, which enterprise moves in the direction of a convergence of disparate meanings. In contrast, the experience of reading Bion's later work conveys a sense of psychoanalysis as a process involving a movement toward infinite expansion of meaning. The author offers a detailed account of an analytic experience which he discusses from a point of view informed by Bion's work, particularly his late work.

History, 20th Century↗

PubMedDate not supplied

Use of cloze and contrast word procedures in repeated storybook reading: targeting multiple domains.

UNLABELLED: The purposes of this study were: (1) to implement an intervention approach for children with language and phonological impairments, targeting multiple linguistic domains within a unitary activity, and (2) to investigate whether any observed changes in selected outcome measures were associated with particular scaffolding procedures. The intervention approach employed a variety of scaffolding procedures (cloze procedures; cloze procedures with expansions; contrast words) within an interactive repeated storybook reading activity. It was delivered across 12 sessions to three kindergarten children with language and phonological impairments. Pre-treatment and post-treatment probes, together with treatment data, provided indices of the semantic and phonological complexity of the participants' utterances. Changes in complexity levels were observed in all participants. Associations between increases in outcome measures and use of particular scaffolding techniques were identified. LEARNING OUTCOMES: (1) The reader will learn a rationale for use of cloze procedures, cloze procedures with expansions, and contrast words during repeated storybook reading as an intervention for some children with both language and phonological disorders. (2) The reader will learn how to implement cloze procedures, cloze procedures with expansions, and contrast words during repeated storybook reading. (3) The reader will learn how various outcome measures (e.g., level of semantic complexity) may be used to track change in performance over time.

Articulation Disorders↗

PubMed2006

The debate over dopamine's role in reward: the case for incentive salience.

INTRODUCTION: Debate continues over the precise causal contribution made by mesolimbic dopamine systems to reward. There are three competing explanatory categories: 'liking', learning, and 'wanting'. Does dopamine mostly mediate the hedonic impact of reward ('liking')? Does it instead mediate learned predictions of future reward, prediction error teaching signals and stamp in associative links (learning)? Or does dopamine motivate the pursuit of rewards by attributing incentive salience to reward-related stimuli ('wanting')? Each hypothesis is evaluated here, and it is suggested that the incentive salience or 'wanting' hypothesis of dopamine function may be consistent with more evidence than either learning or 'liking'. In brief, recent evidence indicates that dopamine is neither necessary nor sufficient to mediate changes in hedonic 'liking' for sensory pleasures. Other recent evidence indicates that dopamine is not needed for new learning, and not sufficient to directly mediate learning by causing teaching or prediction signals. By contrast, growing evidence indicates that dopamine does contribute causally to incentive salience. Dopamine appears necessary for normal 'wanting', and dopamine activation can be sufficient to enhance cue-triggered incentive salience. Drugs of abuse that promote dopamine signals short circuit and sensitize dynamic mesolimbic mechanisms that evolved to attribute incentive salience to rewards. Such drugs interact with incentive salience integrations of Pavlovian associative information with physiological state signals. That interaction sets the stage to cause compulsive 'wanting' in addiction, but also provides opportunities for experiments to disentangle 'wanting', 'liking', and learning hypotheses. Results from studies that exploited those opportunities are described here. CONCLUSION: In short, dopamine's contribution appears to be chiefly to cause 'wanting' for hedonic rewards, more than 'liking' or learning for those rewards.

Animals↗

PubMed1993

Effects of discrimination learning on the rat amygdala dopamine release: a microdialysis study.

Extracellular levels of dopamine (DA) and its metabolites were monitored with the in vivo microdialysis method in the amygdala of rats while and after they performed a discrimination learning task or a non-discrimination task. A group of rats was trained to discriminate between lamp-on and lamp-off states under an operant-type learning procedure. After a stable discriminative behavior was established, a dialysis probe was inserted into the basolateral amygdaloid nucleus of each rat. The concentrations of DA and its metabolite 3,4-dihydroxyphenylacetic acid significantly increased during the learning sessions as compared to their basal levels. In contrast, another group of rats trained on a similar, but non-discriminative task showed no such increases. These results suggest that the dopaminergic neural systems in the basolateral amygdaloid nucleus are activated during ongoing behavior maintained under the discrimination learning situation.

Amygdala↗

PubMed1999

On the dominance of unidimensional rules in unsupervised categorization.

In several experiments, observers tried to categorize stimuli constructed from two separable stimulus dimensions in the absence of any trial-by-trial feedback. In all of the experiments, the observers were told the number of categories (i.e., two), they were told that perfect accuracy was possible, and they were given extensive experience in the task (i.e., 800 trials). When the boundary separating the contrasting categories was unidimensional, the accuracy of all observers improved significantly over blocks (i.e., learning occurred), and all observers eventually responded optimally. When the optimal boundary was diagonal, none of the observers responded optimally. Instead they all used some sort of suboptimal unidimensional rule. In a separate feedback experiment, all observers responded optimally in the diagonal condition. These results contrast with those for supervised category learning; they support the hypothesis that in the absence of feedback, people are constrained to use unidimensional rules.

Adult↗

PubMed1998

Comparative effects of schizophrenia and temporal lobe epilepsy on memory.

The goal of this study was to further characterize episodic memory functioning in schizophrenia. This study compared verbal and visual learning and memory performance in (1) patients with schizophrenia (N = 35), (2) patients with temporal lobe epilepsy (TLE; N = 30), and (3) normal controls (N = 25). Results indicated significant memory impairments in patients with schizophrenia and TLE. "Savings" score measures of memory decay showed that the loss of information in schizophrenia and TLE was approximately equal, and quantitatively mild compared to that found in most neurologic groups with memory disorders. The severe difficulty shown by the schizophrenia group on a task of incidental recall suggested that the absence of instructional set added to a vulnerability to memory deficit. In contrast, relatively mildly impaired performance on paired associate learning suggested that patients with schizophrenia benefited from retrieval cues, multiple trials, and short (nonsupraspan) informational loads. Because patients with schizophrenia consisted of a relatively nonchronic sample with a mean IQ of 99.7, their memory disorder could not be attributed to schizophrenic dementia, nor was it accounted for by other potential confounds. Patients with schizophrenia, even those relatively early in the course of illness, have a mild episodic memory disorder.

Adolescent↗

PubMed1993

Segmentation of medical images through competitive learning.

In image analysis applications, segmentation of gray-level images into meaningful regions is an important low-level processing step. Various approaches to segmentation investigated in the literature, in general, use either local information of gray-level values of pixels (region growing based methods, for example) or the global information (histogram thresholding based methods, for example). Application of these approaches for segmenting medical images often does not provide satisfactory results. Medical images are usually characterized by low local contrast and noisy or faded features causing unacceptable performance of local information based segmentation methods. In addition, because of a large amount of structural information found in medical images, global information based segmentation methods yield inadequate results in region extraction. We present a novel approach to image segmentation that combines local contrast as well as global gray-level distribution information. The presented method adaptively learns useful features and regions through the use of a normalized contrast function as a measure of local information and a competitive learning based method to update region segmentation incorporating global information about the gray-level distribution of the image. In this paper, we present the framework of such a self organizing feature map, and show the results on simulated as well as real medical images.

Algorithms↗

PubMed1991

Dementia praecox as a failure of neoteny.

The theory of neoteny assumes that adult animals that are higher on the phylogenetic scale retain juvenile characteristics for greater periods of their lifetime. This hypothesis would account for the continuation of curiosity, learning and playfulness in humans and other higher primates in contrast to less evolved mammals. The failure of the neoteny process could result in humans that have lost these juvenile characteristics and lack motivation, curiosity and the capacity to learn freely. These features are indicative of the negative symptoms of dementia praecox, a chronic mental illness that strikes individuals as they become adults. It is postulated that a possible mechanism in the etiology of dementia praecox is the failure of regulator genes to program structural genes to produce enzymes necessary for neoteny. Positive symptoms of the disorder may be conceptualized as the organisms aberrant response to this activation failure. The role of regulator genes in chronic illness may prove a significant avenue for further investigation.

Adolescent↗