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Learning Phase (learning + phase)

Distribution by Scientific Domains

Medical Sciences	28%
Life Sciences	28%
Psychology	14%
Information Science and Computing	14%

Selected Abstracts

Sensori-motor experience leads to changes in visual processing in the developing brain

DEVELOPMENTAL SCIENCE, Issue 2 2010
Karin Harman James
Since Broca's studies on language processing, cortical functional specialization has been considered to be integral to efficient neural processing. A fundamental question in cognitive neuroscience concerns the type of learning that is required for functional specialization to develop. To address this issue with respect to the development of neural specialization for letters, we used functional magnetic resonance imaging (fMRI) to compare brain activation patterns in pre-school children before and after different letter-learning conditions: a sensori-motor group practised printing letters during the learning phase, while the control group practised visual recognition. Results demonstrated an overall left-hemisphere bias for processing letters in these pre-literate participants, but, more interestingly, showed enhanced blood oxygen-level-dependent activation in the visual association cortex during letter perception only after sensori-motor (printing) learning. It is concluded that sensori-motor experience augments processing in the visual system of pre-school children. The change of activation in these neural circuits provides important evidence that ,learning-by-doing' can lay the foundation for, and potentially strengthen, the neural systems used for visual letter recognition. [source]

Effects of Word and Fragment Writing During L2 Vocabulary Learning

FOREIGN LANGUAGE ANNALS, Issue 4 2007
Joe Barcroft
This study examined how writing (copying) target words and word fragments affects intentional second language (L2) vocabulary learning. English-speaking first-semester learners ofSpanish attempted to learn 24 Spanish nouns via word-picture repetition in three conditions: (1) word writing, (2) fragment writing, and (3) no writing. After the learning phase, the participants completed productive (picture-to-L2) and recpectively oriented (L2-to-first language) posttests. Vocabulary learning scores in the no-writing condition were higher than in the other two conditions and higher in the word-writing condition than in the fragment-writing condition. These fmdings provide new evidence on how forced Output without access to meaning can detract from early word learning by exhausting processing resources needed to encode new word forms. The pedagogical implications of the study call for language instructors to rethink the practice of encouraging students to write down a word to remember it. [source]

The retrieval of learned sequences engages the hippocampus: Evidence from fMRI

HIPPOCAMPUS, Issue 9 2009
Robert S. Ross
Abstract Computational models suggest that the hippocampus plays an important role in the retrieval of sequences. However, empirical evidence supporting hippocampal involvement during sequence retrieval is lacking. The current study used functional magnetic resonance imaging (fMRI) to examine the role of the human hippocampus during the learning and retrieval of sequences. Participants were asked to learn four sequences comprised of six faces each. An overlapping condition, where sequences shared common elements, was comprised of two sequences in which two identical faces were shown as the middle images of both sequences. A nonoverlapping condition contained two sequences that did not share any faces between them. A third random condition contained two sets of six faces that were always presented in a random order. The fMRI data were split into a learning phase and an experienced phase based upon each individual's behavioral performance. Patterns of hippocampal activity during presentation, delay, and choice periods were assessed both during learning (learning phase) and after subjects learned the sequences to criteria (experienced phase). The results revealed hippocampal activation during sequence learning, consistent with previous findings in rats and humans. Critically, the current results revealed hippocampal activation during the retrieval of learned sequences. No difference in hippocampal activation was seen between the overlapping and nonoverlapping sequences during either sequence learning or retrieval of sequences. The results extend our current knowledge by providing evidence that the hippocampus is active during the retrieval of learned sequences, consistent with current computational models of sequence learning and retrieval. © 2009 Wiley-Liss, Inc. [source]

Hippocampal lesions and discrimination performance of mice in the radial maze: Sparing or impairment depending on the representational demands of the task

HIPPOCAMPUS, Issue 2 2003
Nicole Etchamendy
Abstract The effects of ibotenate hippocampal lesions on discrimination performance in an eight-arm radial maze were investigated in mice, using a three-stage paradigm in which the only parameter that varied among stages was the way the arms were presented. In the initial learning phase (stage 1), animals learned the valence or reward contingency associated with six (three positive and three negative) adjacent arms of the maze using a successive (go/no-go) discrimination procedure. In the first test phase (stage 2), the six arms were grouped into three pairs, so that on each trial, the subject was faced with a choice between two adjacent arms of opposite valence (concurrent two-choice discrimination). In the second test phase (stage 3), the subject was faced with all six arms simultaneously (six-choice discrimination). Hippocampal-lesioned mice acquired the initial learning phase at a near-normal rate but behaved as if they had learned nothing when challenged with the two-choice discriminations at stage 2. In contrast, they behaved normally when confronted with the six-choice discrimination at stage 3. Detailed examination of within- and between-stage performance suggests that hippocampal-lesioned mice perform as intact mice when presentation of the discriminanda encourages the storage and use of separate representations (i.e., in initial learning and six-choice discrimination testing), but that they fail in test situations that involve explicit comparisons between such separate representations (two-choice discriminations), hence requiring the use of relational representations. Hippocampus 2003;13:197,211. © 2003 Wiley-Liss, Inc. [source]

The dynamic network subserving the three phases of cognitive procedural learning

HUMAN BRAIN MAPPING, Issue 12 2007
Valérie Hubert
Abstract Cognitive procedural learning is characterized by three phases (cognitive, associative, and autonomous), each involving distinct processes. We performed a behavioral study and a positron emission tomography (PET) activation study using the Tower of Toronto task. The aim of the behavioral study was to determine cognitive predictors for the length of each of the three learning phases, in order to preselect subjects for the PET study. The objective of the second study was to describe the cerebral substrates subtending these three phases. Contrasted with a reference (motor) task, the cognitive phase activated the prefrontal cortex, cerebellum, and parietal regions, all of which became less active as learning progressed. The associative phase was characterized by the activation of the occipital regions, right thalamus, and caudate nucleus. During the autonomous phase, new regions were involved, including the left thalamus and an anterior part of the cerebellum. These results, by employing a direct comparison between phases, provide the first evidence of the involvement and the time course of activation of different regions in each learning phase, in accordance with current models of cognitive procedural learning. The involvement of a frontoparietal network suggests the use of strategies in problem solving during the cognitive phase. The involvement of the occipital regions during the associative and autonomous phase suggests the intervention of mental imagery. Lastly, the activation of the cerebellum during the autonomous phase is consistent with the fact that performance in this phase is determined by psychomotor abilities. Hum Brain Mapp, 2007. © 2007 Wiley-Liss, Inc. [source]

Adaptive critic design using non-linear network structures

INTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 6 2003
Ognjen Kuljaca
Abstract A neural net (NN)/fuzzy logic (FL) adaptive critic controller is described. This structure takes advantage of the decision-making properties of a FL system to critique and tune a NN action-generating network. The stability of the proposed structure is proven. NN and fuzzy weight tuning algorithms are given that do not require complicated initialization procedures or any off-line learning phase. Tracking and bounded NN weights and control signals are guaranteed. The adaptive fuzzy critic controller given here is a model-free controller' in the sense that it works for any system in a prescribed class without the need for extensive modeling and preliminary analysis to find a regression matrix'. There is no linearity in the parameter (LIP) requirement. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Matching pursuit-based shape representation and recognition using scale-space

INTERNATIONAL JOURNAL OF IMAGING SYSTEMS AND TECHNOLOGY, Issue 5 2006
François Mendels
Abstract In this paper, we propose an analytical low-level representation of images, obtained by a decomposition process, namely the matching pursuit (MP) algorithm, as a new way of describing objects through a general continuous description using an affine invariant dictionary of basis function (BFs). This description is used to recognize multiple objects in images. In the learning phase, a template object is decomposed, and the extracted subset of BFs, called meta-atom, gives the description of the object. This description is then naturally extended into the linear scale-space using the definition of our BFs, and thus providing a more general representation of the object. We use this enhanced description as a predefined dictionary of the object to conduct an MP-based shape recognition task into the linear scale-space. The introduction of the scale-space approach improves the robustness of our method: we avoid local minima issues encountered when minimizing a nonconvex energy function. We show results for the detection of complex synthetic shapes, as well as real world (aerial and medical) images. © 2007 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 16, 162,180, 2006 [source]

Adaptive recurrent neural network control of biological wastewater treatment

INTERNATIONAL JOURNAL OF INTELLIGENT SYSTEMS, Issue 2 2005
Ieroham S. Baruch
Three adaptive neural network control structures to regulate a biological wastewater treatment process are introduced: indirect, inverse model, and direct adaptive neural control. The objective is to keep the concentration of the recycled biomass proportional to the influent flow rate in the presence of periodically acting disturbances, process parameter variations, and measurement noise. This is achieved by the so-called Jordan Canonical Recurrent Trainable Neural Network, which is a completely parallel and parametric neural structure, permitting the use of the obtained parameters, during the learning phase, directly for control system design. Comparative simulation results confirmed the applicability of the proposed control schemes. © 2005 Wiley Periodicals, Inc. Int J Int Syst 20: 173,193, 2005. [source]

Machine learning for Arabic text categorization

JOURNAL OF THE AMERICAN SOCIETY FOR INFORMATION SCIENCE AND TECHNOLOGY, Issue 8 2006
Rehab M. Duwairi
In this article we propose a distance-based classifier for categorizing Arabic text. Each category is represented as a vector of words in an m -dimensional space, and documents are classified on the basis of their closeness to feature vectors of categories. The classifier, in its learning phase, scans the set of training documents to extract features of categories that capture inherent category-specific properties; in its testing phase the classifier uses previously determined category-specific features to categorize unclassified documents. Stemming was used to reduce the dimensionality of feature vectors of documents. The accuracy of the classifier was tested by carrying out several categorization tasks on an in-house collected Arabic corpus. The results show that the proposed classifier is very accurate and robust. [source]

The reverse-caricature effect revisited: Familiarization with frontal facial caricatures improves veridical face recognition

APPLIED COGNITIVE PSYCHOLOGY, Issue 5 2009
Jobany Rodríguez
Prior research suggests that recognition of a person's face can be facilitated by exaggerating the distinctive features of the face during training. We tested if this ,reverse-caricature effect' would be robust to procedural variations that created more difficult learning environments. Specifically, we examined whether the effect would emerge with frontal rather than three-quarter views, after very brief exposure to caricatures during the learning phase and after modest rotations of faces during the recognition phase. Results indicate that, even under these difficult training conditions, people are more accurate at recognizing unaltered faces if they are first familiarized with caricatures of the faces, rather than with the unaltered faces. These findings support the development of new training methods to improve face recognition. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Multicentre validation study of sentinel node biopsy for staging in breast cancer

BRITISH JOURNAL OF SURGERY (NOW INCLUDES EUROPEAN JOURNAL OF SURGERY), Issue 10 2005
L. Bergkvist
Background: The aim of this study was to validate sentinel node biopsy for axillary staging after the initial learning phase, and to analyse factors associated with false-negative biopsies. Methods: Some 675 patients, who had standard sentinel node biopsy followed by level I and II axillary clearance in one of 20 hospitals in Sweden and were operated on by 36 different surgeons, were recruited prospectively. Results: The overall detection rate was 94·5 per cent. It varied between surgeons but was not influenced by the number of operations per surgeon. Moreover, it was lower among older patients. The overall false-negative rate was 7·7 per cent. This rate was not affected by patient age, tumour histological type or Elston grade, but was increased in patients with multifocal tumours. Some 21 per cent of patients with a multifocal tumour diagnosed on postoperative histopathological analysis had a false-negative biopsy compared with 5·6 per cent of those with unifocal tumours (P = 0·004). Conclusion: Sentinel node biopsy was shown to be a reliable method for axillary staging of unifocal breast tumours. Copyright © 2005 British Journal of Surgery Society Ltd. Published by John Wiley & Sons, Ltd. [source]

Multicentre study of detection and false-negative rates in sentinel node biopsy for breast cancer

BRITISH JOURNAL OF SURGERY (NOW INCLUDES EUROPEAN JOURNAL OF SURGERY), Issue 12 2001
Dr L. Bergkvist
Background: Sentinel node biopsy has recently evolved as a means of staging the axilla in breast cancer with minimal surgical trauma. The aim of this prospective multicentre study was to identify factors that influencd the detection and false-negative rates during the learning phase. Methods: Data on all 498 sentinel node biopsies performed between August 1997 and December 1999 in Sweden were collected. Results: A sentinel node was found in 450 patients (90 per cent). Preoperative scintigraphy visualized 83 per cent of all sentinel nodes. The detection rate was higher with same-day injection of tracer than with injection the day before (96 versus 86 per cent; P < 0·01). Dye injected less than 5 min or more than 30 min before the start of the operation lowered the detection rate (less than 60 per cent versus more than 65 per cent; P = 0·02). The detection rate varied from 61 to 100 per cent between surgeons. The false-negative rate was 11 per cent. The presence of multiple tumour foci and a high S-phase fraction increased the risk of a false-negative sentinel node, whereas the number of operations performed by each surgeon was less important. Conclusion: Training of the individual surgeon influenced the detection rate, as did timing of tracer and dye injection. The false-negative rate seemed to be related to biological factors. © 2001 British Journal of Surgery Society Ltd [source]

Sensitivity to the acceleration of looming stimuli

CLINICAL & EXPERIMENTAL OPHTHALMOLOGY, Issue 3 2003
James Trewhella BSc(Hons)
Abstract The aim of this study was to determine if observers could discriminate between looming stimuli simulating targets approaching the observers at either constant or non-constant speeds. Discrimination between accelerating and constant-speed approaches improved after 70,90 trials for accelerations >2 m/s2. For lower accelerations the ability to discriminate was poor regardless of the trial number. Following the learning phase, observers were able to identify accelerating targets from constant-speed approaches fairly consistently at performance levels of 70,75% for accelerations as low as 4 m/s2 and at 80,96% for accelerations of 6,14 m/s2. Observers' accuracy in identifying decelerating from constant-speed targets did not increase as a function of increasing deceleration. In fact, observers had a slight bias to select the constant-speed stimulus as being the decelerating stimulus. In summary, the sensitivity to acceleration for simulated motion in depth is poor, but increases as acceleration increases and sensitivity to acceleration is far greater than for deceleration. [source]