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PubMed2004

Consolidation of dynamic motor learning is not disrupted by rTMS of primary motor cortex.

Motor skills, once learned, are often retained over a long period of time. However, such learning first undergoes a period of consolidation after practice. During this time, the motor memory is susceptible to being disrupted by the performance of another motor-learning task. Recently, it was shown that repetitive transcranial magnetic stimulation (rTMS) over the primary motor cortex could disrupt the retention of a newly learned ballistic task in which subjects had to oppose their index finger and thumb as rapidly as possible. Here we investigate whether the motor cortex is similarly involved during the consolidation that follows learning novel dynamics. We applied rTMS to primary motor cortex shortly after subjects had either learned to compensate for a dynamic force field applied to their index finger or learned a ballistic finger abduction task. rTMS severely degraded the retention of the learning for the ballistic task but had no effect on retention of the dynamic force-field learning. This suggests that, unlike learning of simple ballistic skills, learning of dynamics may be stored in a more distributed manner, possibly outside the primary motor cortex.

Adult↗

PubMed2003

Structure-stability-function relationships of dendritic spines.

Dendritic spines, which receive most of the excitatory synaptic input in the cerebral cortex, are heterogeneous with regard to their structure, stability and function. Spines with large heads are stable, express large numbers of AMPA-type glutamate receptors, and contribute to strong synaptic connections. By contrast, spines with small heads are motile and unstable and contribute to weak or silent synaptic connections. Their structure-stability-function relationships suggest that large and small spines are "memory spines" and "learning spines", respectively. Given that turnover of glutamate receptors is rapid, spine structure and the underlying organization of the actin cytoskeleton are likely to be major determinants of fast synaptic transmission and, therefore, are likely to provide a physical basis for memory in cortical neuronal networks. Characterization of supramolecular complexes responsible for synaptic memory and learning is key to the understanding of brain function and disease.

Animals↗

PubMed2002

Multiprofessional palliative care in a general hospital: education and training needs.

Palliative care for those who need it should be an integral part of National Health Service (NHS) practice in all settings in the UK. This study used a focus group and individual structured questionnaires, completed during a semi-structured interview, to gain an insight into how different professionals in the hospital view palliative care. An assessment was made of their understanding of it, previous training and current knowledge. The respondents also discussed training needs and personal experiences. The findings show that previous training was variable but, in general, relatively young and inexperienced staff were working in the hospital under enormous pressures of workload, staff shortages and without experienced role models from whom to learn the complexities of palliative care. Communication difficulties focused around the lack of support and the inherent problems of multidisciplinary team working resulting in frustration and less than optimum care being given. Rapid staff turnover compounded the problems. Although staff were keen to learn, clinical workload always took priority over training. The following recommendations arose from the study: undergraduate training should be standardized, and postgraduate training and support should be ongoing and flexible to accommodate the diversities of knowledge and difficulties encountered in attending set sessions.

Attitude of Health Personnel↗

PubMed1993

Learning that food is inedible in freely behaving Aplysia californica.

Freely behaving Aplysia californica can learn that food is inedible. Animals were given access to seaweed tied into canvas and attached to a force transducer. Animals repeatedly found the stimulus, attempted to ingest it, and failed. The force transducer provided an objective record of the number of attempts made by the animal to ingest the stimulus, the length of each attempt, and its intensity (i.e., peak force exerted). Within 2.5 hr, animals showed significant declines in these 3 measures of response to the stimulus. When exposed to the same stimulus the next day, animals showed more rapid declines in responsiveness, which indicate a retention of learning. Training appeared to be specific: Responses to the seaweed Laurencia of animals previously trained on the seaweed Ulva do not differ from the responses of naive animals to Laurencia.

Animals↗

PubMed1998

Computational learning reveals coiled coil-like motifs in histidine kinase linker domains.

The recent rapid growth of protein sequence databases is outpacing the capacity of researchers to biochemically and structurally characterize new proteins. Accordingly, new methods for recognition of motifs and homologies in protein primary sequences may be useful in determining how these proteins might function. We have applied such a method, an iterative learning algorithm, to analyze possible coiled coil domains in histidine kinase receptors. The potential coiled coils have not yet been structurally characterized in any histidine kinase, and they appear outside previously noted kinase homology regions. The learning algorithm uses a combination of established sequence patterns in known coiled coil proteins and histidine kinase sequence data to learn to recognize efficiently this coiled coil-like motif in the histidine kinases. The common appearance of the structural motif in a functionally important part of the receptors suggests hypotheses for kinase regulation and signal transduction.

Algorithms↗

PubMed1984

Monkeys with combined amygdalo-hippocampal lesions succeed in object discrimination learning despite 24-hour intertrial intervals.

Monkeys with combined amygdalo-hippocampal removal show severe impairments on visual memory tasks after delays of only a minute or two, yet they learn visual discrimination habits about as quickly as normal animals with intertrial intervals of the same duration. In an attempt to resolve this discrepancy between abnormally rapid forgetting and successful retention, tests were conducted to determine whether discrimination learning would be prevented in animals with limbic lesions if intertrial intervals lasted 24 hr. The results showed that as long as the lesion did not encroach on inferior temporal cortex, the operated animals could acquire concurrent sets of 20 object discrimination habits at the same rate as normal animals, in an average of about 10 trials per set. The findings suggest that learning and retention processes are divisible into a mechanism for memory formation that is dependent on the limbic system and a mechanism for habit formation that is not.

Amygdala↗

PubMed1975

Acceptable and controversial approaches to treating the child with learning disabilities.

There are many professionals in multiple disciplines developing approaches for helping children with learning disabilities. Much of these data and reports are published in journals normally not read by physicians. On occasion, such publications are reported in newspapers or lay magazines. Thus, parents may know of ideas and suggestions before the professional. It is understandable that the parent of a handicapped child would continually seek out improved ways of helping his or her child. The treatment of choice is basically special education. Medication will minimize the hyperactivity and distractability; psychotherapy may minimize the emotional effects. However, special educational therapy for the underlying learning disabilities is essential. No one yet has a rapid or "guaranteed" cure. Parents are often caught in the middle. They turn to their physician for guidance. It is the purpose of this paper to review the significant literature in an effort to assist the family physician in providing this guidance.

Anti-Anxiety Agents↗

PubMed2004

Circadian modulation of sequence learning under high and low sleep pressure conditions.

Humans are able to learn complex sequences even without conscious awareness. We have studied the repercussions of circadian phase and sleep pressure on the ability to learn structured sequences using a serial reaction time task (SRT). Sixteen young healthy volunteers were studied in a 40-h "constant posture protocol" under high sleep pressure (i.e. sleep deprivation) and low sleep pressure conditions (i.e. sleep satiation attained by multiple naps). Here we show that learning of different sequence structures improved after multiple naps, in particular after naps that followed the circadian peak of rapid-eye-movement (REM) sleep. This situation following sleep contrasted with the lack of learning without sleep. We have evidenced that the observed amelioration of learning new sequences came about by memorizing short sub-fragments ("chunks") of the sequence train. However, SRT performance did not deteriorate under high sleep pressure, despite the high level of sleepiness. Our data indicate that sequence learning is modulated by circadian phase, and the neurophysiological medium required for this type of learning is related to sleep.

Adult↗

PubMed2005

Olfactory learning-induced morphological modifications in single dendritic spines of young rats.

Learning-related morphological modifications in single dendritic spines were studied quantitatively in the brains of young Sprague-Dawley rats. We have previously shown that olfactory discrimination rule-learning results in transient physiological and morphological modifications in piriform cortex pyramidal neurons. In particular, spine density along the apical dendrites of neurons from trained rats is increased after learning. The aim of the present study was to identify and describe olfactory learning-induced modifications in the morphology of single spines along apical dendrites of the same type of neurons. By using laser-scanning confocal microscopy, we show that 3 days after training completion spines on neurons from olfactory discrimination trained rats are shorter as compared to spines on neurons from control rats. Further analysis revealed that spine shortening attributed to olfactory discrimination learning derives from shortening of spine head and not from shortening of spine neck. In addition, detailed analysis of spine head volume suggests that spines with large heads are absent after learning. As spine head size may be related to the efficacy of the synapse it bears, we suggest that modifications in spine head dimensions following olfactory rule-learning enhance the cortical network ability to enter into a 'learning mode', in which memories of new odours can be acquired rapidly and efficiently.

Analysis of Variance↗

PubMed1990

Chronic infusions of GABA into the medial frontal cortex of the rat induce a reversible delayed spatial alternation deficit.

The effects of bilateral infusions of GABA into the medial frontal cortex of the rat were studied in a delayed spatial alternation task. It was found that GABA (500 mM, 1 microliter/h during 7 days) impaired the performance of the rats in the previously learned task. Upon interruption of the treatment, the animals rapidly recovered normal performance scores. The results show that GABA infusions produce functional deficits similar to those produced by lesions of the frontal cortex. Moreover, the deficits are reversible upon interruption of the treatment. This technique may therefore be a useful tool for studying frontal lobe functions and the involvement of GABAergic mechanisms in cognitive processes.

Animals↗

PubMed2001

Effect of innate direction bias on T-maze learning in rats: implications for research.

Adult, male Wistar rats showed substantial left (22.2%) or right (52.8%) bias in spontaneous arm preference in the T-maze; this bias was consistent over 2 days of testing separated by a 30 day interval. Left and right biased rats learnt very rapidly when trained to enter the arm ipsilateral to the bias; learning was significantly poorer or did not occur in the contralateral arm. This contralateral learning difficulty was particularly evident when transfer of learning was assessed. Right-biased rats were more impaired in contralateral learning than left-biased rats. Unbiased rats (25%) also showed learning difficulties. This study has important implications for spatial tasks of learning and memory; with specific reference to the T maze, it is concluded that animals should be preselected for capacity to learn in both arms, randomization into experimental and control groups should be stratified for spontaneous arm bias, and original learning should be directed towards the contralateral arm while transfer of learning, if required, can be directed into the ipsilateral arm.

Animals↗

PubMedDate not supplied

Pharmacological antagonism of tyrosine kinases and MAP kinase in brainstem blocks taste aversion learning in mice.

Although c-Fos induction in the brainstem is a reliable correlate of taste aversion learning and appears necessary for the encoding of the unconditioned stimulus, little is known about the intracellular signaling pathways in the brainstem that regulate c-Fos expression during taste aversion learning. Infusion of the tyrosine kinase inhibitor genistein and the MAP kinase kinase (MEK) inhibitor PD98059 into the fourth ventricle of mice potently blocks acquisition of a learned taste aversion. The unconditioned stimulus LiCl produces a rapid and robust phosphorylation of MAP kinase, as revealed by immunohistochemistry with an antibody specific to the dually phosphorylated active form of MAP kinase. This immunoreactivity is localized to the same region of the intermediate nucleus tractus solitarius in which we have shown large increases in c-Fos immunoreactive cells, suggesting that in at least a subset of these cells, MAP kinase activation may lead to c-fos induction.

Animals↗

PubMed1993

The ClusNet algorithm and time series prediction.

This paper describes a novel neural network architecture named ClusNet. This network is designed to study the trade-offs between the simplicity of instance-based methods and the accuracy of the more computational intensive learning methods. The features that make this network different from existing learning algorithms are outlined. A simple proof of convergence of the ClusNet algorithm is given. Experimental results showing the convergence of the algorithm on a specific problem is also presented. In this paper, ClusNet is applied to predict the temporal continuation of the Mackey-Glass chaotic time series. A comparison between the results obtained with ClusNet and other neural network algorithms is made. For example, ClusNet requires one-tenth the computing resources of the instance-based local linear method for this application while achieving comparable accuracy in this task. The sensitivity of ClusNet prediction accuracies on specific clustering algorithms is examined for an application. The simplicity and fast convergence of ClusNet makes it ideal as a rapid prototyping tool for applications where on-line learning is required.

Algorithms↗

PubMed2001

Learning and evaluation in medical education.

An educational experience is a complex event, which involves four distinct common places: learner, curriculum, milieu and teacher. Medical education is a unique form of educational experience. The learner is almost always an adult. The teacher is not necessarily trained to teach. Because of rapid changes in knowledge it is very dynamic. Life-long learning and evaluation are mandatory, for the student as well as the medical practitioner. This communication highlights some issues concerning learning and evaluation, as applicable to medical education, including the concept of learning by objectives, learning approaches, study strategies, learning methods; the purposes of evaluation, self-evaluation and common assessment methods. This is intended to create some awareness, in the medical student, resident or medical teacher of the need to begin to learn how to learn and demystify evaluation.

Education, Medical↗

PubMed1994

Explicit memory, procedural learning and lexical priming in Alzheimer's disease.

Different aspects of memory functions were studied in two groups of patients with Alzheimer's disease (AD) and in normal elderly controls. The tests included: explicit memory tests with free and cued recall, and recognition measures; learning of a motor skill; learning of a perceptual skill with verbal material; a priming task with the word stem completion paradigm. The data confirmed that, besides severe impairment for all measures of explicit memory, AD patients were able to learn and retain normally a motor skill in the rotor pursuit task, even across a long retention interval. Moreover, sparing of procedural learning was not restricted to motor tasks, since patients learned normally a mirror-reading task, demonstrating (a) rapid acquisition of the procedure, and (b) acquisition of item-specific information for repeated words. This last effect is accounted for in terms of repetition priming effects rather than of explicit memory strategies, since patients had also normal repetition effect in the word stem completion paradigm.

Aged↗

PubMed2005

[Sentinel lymphonodectomy in breast cancer - our own experience. Part 2].

UNLABELLED: The aim of this investigation was to document the personal learning curve of the sentinel lymphonodectomy in breast surgery and to compare it with the experiences of other authors. RESULTS: Between July 1999 and May 2004, the authors performed 218 sentinel lymphonodectomies, 48 of them during the 24-month evaluation period with consecutive full axillary dissection. The overall detection rate was 212/218 or 97.2%, while during the evaluation period it was 38/48 or 89.6% (failures were procedures No. 6, 7, 22, 24 and 47). Among the first 48 cases, 24 had histologically proven metastasis to one or more of the axillary lymph nodes. In 3 of these cases, we were not able to detect a sentinel lymph node, and 4 times the sentinel lymph node was false-negative after rapid section. The false-negative results during the learning period belonged to cases No. 2, 10, 23 and 29 (4/21 or 19%). From September 2001 until May 2004, the detection rate was over 99% (165/166). DISCUSSION: Our own experience documents the initial difficulties and insecurities with this operative procedure. The common recommendations, i.e. that sentinel lymphonodectomy without axillary clearance should not be offered before having completed one's own learning curve with the aid of experienced surgeons, are to be supported.

Axilla↗

PubMed1999

Emergence of symmetric, modular, and reciprocal connections in recurrent networks with Hebbian learning.

While learning and development are well characterized in feedforward networks, these features are more difficult to analyze in recurrent networks due to the increased complexity of dual dynamics - the rapid dynamics arising from activation states and the slow dynamics arising from learning or developmental plasticity. We present analytical and numerical results that consider dual dynamics in a recurrent network undergoing Hebbian learning with either constant weight decay or weight normalization. Starting from initially random connections, the recurrent network develops symmetric or near-symmetric connections through Hebbian learning. Reciprocity and modularity arise naturally through correlations in the activation states. Additionally, weight normalization may be better than constant weight decay for the development of multiple attractor states that allow a diverse representation of the inputs. These results suggest a natural mechanism by which synaptic plasticity in recurrent networks such as cortical and brainstem premotor circuits could enhance neural computation and the generation of motor programs.

Animals↗

PubMedDate not supplied

The use of computer simulation in teaching clinical diagnosis.

Previous studies have shown that feedback of the weighting used in making complex judgements can greatly improve learning when the correct weighting is known. This paper describes the application to teaching medical diagnosis of a microcomputer program which calculates and displays factor weighting based on answers to clinical case simulations. In one application, students learning to diagnose urinary tract infusion with computer feedback of weighting progressed much more rapidly than a control group who received outcome feedback alone. Other applications in the clinical setting suggest that this type of learning can improve diagnostic accuracy and predictive calibration through more accurate assimilation of the clinical information available.

Computer Simulation↗