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At least 1,603 records · Page 89Linked to original sources
PubMed1984

Signature size in the psychiatric diagnosis: a significant clinical sign?

To test the hypothesis that patients' signatures may have a useful potential in making psychiatric diagnoses, the authors conducted a correlation study between signature sizes and psychiatric diagnoses. 252 medical records at St. Louis State Hospital in Missouri, USA, were randomized for the measurement of the signature sizes and assessment of DSM-III diagnoses. Analysis of variance and pair-wise comparison show that the signature size in the manic group is significantly larger than those of any other categories of psychiatric diagnoses (p less than 0.05), and that the signature size of organic mental disorder is significantly larger than those of the normal group (p less than 0.05). The authors suggest that further studies are needed to develop the clinical significance, if any, for interpreting patients' signatures.

Bipolar Disorder↗
PubMed1979

Field dependency, brain asymmetry and psychophysiological differences.

Field dependent individuals differ psychologically from field independent subjects. They use more primitive defense mechanisms, and are more responsive to social forces around them than field independent subjects. Psychophysiological differences exist between these groups which will be reviewed. Obesity and alcoholism are also related to field dependency, as well as other psychosomatic disorders. Our series of experiments show that field dependent subjects are less left cerebrally dominant, and show most elements (in subclinical form) of a left cerebral lobe (Gerstmann's) syndrome. Implications for psychosomatic medicine are noted in the psychophysiological differences seen.

Amphetamine↗
PubMed1994

Writing tremor after discrete cortical infarction.

BACKGROUND: Hand tremor is a rare manifestation of stroke, and writing tremor has not been reported to be produced by stroke. We describe a patient who developed a unilateral hand tremor mimicking primary writing tremor after discrete cerebral cortical infarction. CASE DESCRIPTION: A 67-year-old man developed mild right hemiparesis. Brain magnetic resonance imaging showed a discrete cortical infarct in the left frontal area. After recovery of motor power, the patient showed significant right hand tremor exclusively during writing or similar motor activities including tooth brushing or shaving. The tremor was temporarily alleviated by clonazepam but persisted until 7 months of follow-up. Medical history suggested that the patient had mild essential tremor, but he did not experience tremor on writing before the onset of stroke. CONCLUSIONS: This observation suggests that unilateral hand tremor mimicking primary writing tremor may be produced by cortical infarction. It remains unclear whether the patient's previous essential tremor played an additional role in the development of this symptom.

Aged↗
PubMed2002

Modulation of the visual word retrieval system in writing: a functional MRI study on the Japanese orthographies.

We used functional magnetic resonance imaging (fMRI) to examine whether the act of writing involves different neuropsychological mechanisms between the two script systems of the Japanese language: kanji (ideogram) and kana (phonogram). The main experiments employed a 2 x 2 factorial design that comprised writing-to-dictation and visual mental recall for kanji and kana. For both scripts, the actual writing produced a widespread fronto-parietal activation in the left hemisphere. Especially, writing of kanji activated the left posteroinferior temporal cortex (lPITC), whereas that of kana also yielded a trend of activation in the same area. Mental recall for both scripts activated similarly the left parietotemporal regions including the lPITC. The writing versus mental recall comparison revealed greater activations in the left sensorimotor areas and right cerebellum. The kanji versus kana comparison showed increased responses in the left prefrontal and anterior cingulate areas. Especially, the lPITC showed a significant task-by-script interaction. Two additional control tasks, repetition (REP) and semantic judgment (SJ), activated the bilateral perisylvian areas, but enhanced the lPITC response only weakly. These results suggest that writing of the ideographic and phonographic scripts, although using the largely same cortical regions, each modulates the visual word-retrieval system according to their graphic features. Furthermore, comparisons with two additional tasks indicate that the activity of the lPITC increases especially in expressive language operations regardless of sensory modalities of the input stimulus.

Acoustic Stimulation↗
PubMed2000

Boosting neural networks.

Boosting is a general method for improving the performance of learning algorithms. A recently proposed boosting algorithm, AdaBoost, has been applied with great success to several benchmark machine learning problems using mainly decision trees as base classifiers. In this article we investigate whether AdaBoost also works as well with neural networks, and we discuss the advantages and drawbacks of different versions of the AdaBoost algorithm. In particular, we compare training methods based on sampling the training set and weighting the cost function. The results suggest that random resampling of the training data is not the main explanation of the success of the improvements brought by AdaBoost. This is in contrast to bagging, which directly aims at reducing variance and for which random resampling is essential to obtain the reduction in generalization error. Our system achieves about 1.4% error on a data set of on-line handwritten digits from more than 200 writers. A boosted multilayer network achieved 1.5% error on the UCI letters and 8.1% error on the UCI satellite data set, which is significantly better than boosted decision trees.

Algorithms↗
PubMed1999

Mixtures of probabilistic principal component analyzers.

Principal component analysis (PCA) is one of the most popular techniques for processing, compressing, and visualizing data, although its effectiveness is limited by its global linearity. While nonlinear variants of PCA have been proposed, an alternative paradigm is to capture data complexity by a combination of local linear PCA projections. However, conventional PCA does not correspond to a probability density, and so there is no unique way to combine PCA models. Therefore, previous attempts to formulate mixture models for PCA have been ad hoc to some extent. In this article, PCA is formulated within a maximum likelihood framework, based on a specific form of gaussian latent variable model. This leads to a well-defined mixture model for probabilistic principal component analyzers, whose parameters can be determined using an expectation-maximization algorithm. We discuss the advantages of this model in the context of clustering, density modeling, and local dimensionality reduction, and we demonstrate its application to image compression and handwritten digit recognition.

Algorithms↗
PubMed1999

Boosted mixture of experts: an ensemble learning scheme.

We present a new supervised learning procedure for ensemble machines, in which outputs of predictors, trained on different distributions, are combined by a dynamic classifier combination model. This procedure may be viewed as either a version of mixture of experts (Jacobs, Jordan, Nowlan, & Hintnon, 1991), applied to classification, or a variant of the boosting algorithm (Schapire, 1990). As a variant of the mixture of experts, it can be made appropriate for general classification and regression problems by initializing the partition of the data set to different experts in a boostlike manner. If viewed as a variant of the boosting algorithm, its main gain is the use of a dynamic combination model for the outputs of the networks. Results are demonstrated on a synthetic example and a digit recognition task from the NIST database and compared with classifical ensemble approaches.

Algorithms↗
PubMed1999

Variational learning in nonlinear gaussian belief networks.

We view perceptual tasks such as vision and speech recognition as inference problems where the goal is to estimate the posterior distribution over latent variables (e.g., depth in stereo vision) given the sensory input. The recent flurry of research in independent component analysis exemplifies the importance of inferring the continuous-valued latent variables of input data. The latent variables found by this method are linearly related to the input, but perception requires nonlinear inferences such as classification and depth estimation. In this article, we present a unifying framework for stochastic neural networks with nonlinear latent variables. Nonlinear units are obtained by passing the outputs of linear gaussian units through various nonlinearities. We present a general variational method that maximizes a lower bound on the likelihood of a training set and give results on two visual feature extraction problems. We also show how the variational method can be used for pattern classification and compare the performance of these nonlinear networks with other methods on the problem of handwritten digit recognition.

Depth Perception↗
PubMed1987

Experiential sampling in the study of multiple personality disorder.

The authors describe the application of experiential sampling, a new time-sampling method, to the assessment of rapid state changes in a woman with multiple personality disorder. She was signaled at random intervals during study periods and asked to provide information on alternate personality switches, amnesia, and mood state. The alternates displayed some characteristics that were as different as those occurring between separate individuals studied previously with this method. There were notable discrepancies between the self-report study data and information reported during therapy hours. The authors conclude that the phenomenology of multiple personality disorder is frequently more complex than is suspected early in the course of treatment.

Adult↗
PubMed1983

Nondyslexic children with combined writing and arithmetic learning disabilities.

A common presenting problem of children in pediatric practice is the constellation of symptoms involving difficulty in completing assignments, trouble with written work, and organizational problems. Typically, these children do not have difficulty with reading but show problems with academic achievement. We have recently studied 29 children, aged 7 to 13, referred for learning problems. They were not dyslexic, that is their reading abilities were normal, but they had significant difficulty with written tests and assignments and problems with arithmetic. In addition to difficulty with eye-hand coordination as measured by a test of visual motor integration, these children showed poor performance on short-term memory tasks when compared with children who do not have writing or arithmetic problems. Suggested treatments include the use of tape recorders, typewriters, and calculators to help compensate for the writing and short-term memory difficulties associated with these learning problems. The pediatrician, acting as child advocate, can exert influence within the traditional school system to gain acceptance for use of learning aids by children with a developmental output disability.

Adolescent↗
PubMedDate not supplied

A case study of the apprenticeship process: another perspective on the apprentice and the scaffolding metaphor.

This study focused on the apprenticeship opportunities in a collaborative writing context. The examination of written artifacts and discursive interactions revealed that collaborative contexts offered unique participatory spaces that allowed students to use their knowledge in ways that exceeded their independent competence. Of note, too, is that the study revealed students' active and constructive role, refuting the perception that most students with disabilities are passive learners in the teaching-learning process. Implications of the study further suggest the importance of peer collaborations in creating successful literacy apprenticeships, as well as in providing teachers with greater insight into the developmental progress and literacy potentials of their students in the context of situated literacy activity.

Child↗