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Biomedical subjects

L J Chapman

Publications and source records attributed to L J Chapman.

At least 19 recordsLinked to original sources
PubMed1992

Monaural and binaural story recall by schizophrenic subjects.

P. Green and other investigators have reported that schizophrenic Ss have poorer recall of stories presented to both ears than to the single best ear (binaural deficit) and poorer recall of stories presented to the left ear than to the right ear (monaural asymmetry) than do normal control Ss. These studies are plagued by potential methodological problems, including differences in overall accuracy, which artifactually affect the difference scores, and scoring methods that are vulnerable to systematic bias. In this study, scores of schizophrenic, bipolar, and normal control Ss on the Auditory Comprehension Test were compared. Scoring bias was avoided by the use of blind scoring and a revised scoring manual, and artifactual effects of accuracy were considered in interpreting the results. Contrary to previous findings, the groups did not differ on either monaural asymmetry or binaural deficit.

Adult↗
PubMed1991

Finger tremor after carbon disulfide-based pesticide exposures.

Index finger tremor accompanying voluntary movement was studied in 19 age-matched control subjects and in 19 grain industry employees chronically exposed to carbon disulfide-based fumigants. Visual judgments of tremor amplitude made by neurologists during clinical examinations equaled the sensitivity of computerized tremor amplitude measurements. Tremor frequency variations detectable only with computerized measurement were present in grain workers with and without increased tremor amplitudes. Frequency differences discriminated between normal subjects and 74% of the grain workers. The distribution of tremor frequency power in the grain workers was often sequestered at 5 to 7 Hz, reminiscent of tremor in idiopathic Parkinson's disease. These findings suggest that the measurement of subtle tremor frequency changes may provide an early indication of chronic carbon disulfide poisoning.

Adult↗
PubMed1990

Facilitation of word recognition by semantic priming in schizophrenia.

Schizophrenic (n = 21), bipolar (n = 18), and normal control subjects (n = 21) were compared on a word recognition measure of semantic priming. The task involved the presentation of related, neutral, and unrelated word pairs; the second word (target word) in each pair was presented in a degraded form. Facilitation was defined as the accuracy of target word recognition for the related word pairs minus accuracy for the neutral word pairs. Titration, achieved by manipulating the degradation of the target word, was used to maintain each subject's overall accuracy for related and neutral items at approximately 50%. This procedure minimized the artifactual effects of overall accuracy on the difference score. Schizophrenics exceeded both normal control subjects and bipolar subjects on facilitation. Bipolar subjects did not differ from control subjects. The results support Maher's hypothesis that semantic priming effects are heightened in schizophrenia.

Attention↗
PubMed1990

Schizophrenic deficit in span of apprehension.

We investigated two hypotheses about the span of apprehension task in schizophrenia: (a) schizophrenics show performance deficit on the forced-choice (FC) version but not on the full-report (FR) version, and (b) schizophrenic impairment on the FC version is greater when the display subtends a wide visual angle than when it subtends a narrow one. Schizophrenic (n = 21) and normal (n = 22) groups were tested on 3 versions of the task. A narrow-angle FC version was matched psychometrically with a wide-angle one by use of a greater number of noise letters in the narrow version. Schizophrenics reported fewer correct letters than normals on the FR version but did not differ on either the wide or the narrow FC versions. The results imply that schizophrenic deficit is not specific to the FC version and that on the FC version, visual angle is not more important than number of noise letters for demonstrating schizophrenic deficit.

Adult↗
PubMed1990

Asymmetrical brain electrical activity discriminates between psychometrically-matched verbal and spatial cognitive tasks.

This study compared the asymmetry of different features of brain electrical activity during the performance of a verbal task (word finding) and a spatial task (dot localization) that had been carefully matched on psychometric properties and accompanying motor activity. Nineteen right-handed subjects were tested. EEG was recorded from F3, F4, C3, C4, P3, and P4, referred to both CZ and computer-derived averaged-ears references, and Fourier transformed. Power in the delta, theta, alpha, and beta bands was computed. There were significant Task X Hemisphere effects in all bands for CZ-referenced data and for the alpha and beta bands for ears-referenced data. The effects were always either greater power suppression in the hemisphere putatively most engaged in task processing or greater power in the opposite hemisphere. Correlations between EEG and task performance indicated that CZ-referenced parietal alpha asymmetry accounted for the most variance in verbal task performance. Power within individual hemispheres or across hemispheres was unrelated to task performance. The findings indicate robust differences in asymmetrical brain physiology that are produced by well-matched verbal and spatial cognitive tasks.

Adult↗
PubMed1990

Differences in frequency of finger tremor in otherwise asymptomatic mercury workers.

Tremor was measured from the index finger during low force, position holding in 18 control subjects and 18 battery workers with low level exposure to mercury. All workers were asymptomatic on clinical neurological examination. No differences were found in average tremor amplitudes between the groups, but statistically significant abnormalities in tremor frequency distribution existed. Tremor power spectra in the group of mercury workers were shifted toward the higher frequencies and compressed into narrow frequency peaks. These results suggest that measurements of finger tremor that evaluate the frequency distribution can produce a higher diagnostic yield than traditional visual clinical judgement. The findings also confirm other reports that currently permitted exposures to mercury are associated with subtle but distinctive differences in tremor accompanying voluntary movement.

Adult↗
PubMed1990

VDT work duration and musculoskeletal discomfort.

Musculoskeletal discomfort, work position, and job stress factors were compared in government office workers grouped according to whether they used video display terminals more or less than 4 hours per day. The results of this study suggest that limits on VDT use to less than 4 hours per day do not necessarily protect against health problems. The occupational health nurse's role in preventive measures useful for alleviating the musculoskeletal health problems of office work are discussed.

Back Pain↗
PubMed1989

Strategies for resolving the heterogeneity of schizophrenics and their relatives using cognitive measures.

The resolution of the heterogeneity of schizophrenics and their relatives using cognitive tasks requires measures of individual differences--usually of differential ability, which is inferred from differential performance. Tasks that are suited for establishing a group's differential ability are often unsuited for measuring individual differences. The problem is that for any group for which Tasks A and B have different mean accuracy, the (A - B) difference scores of individual subjects have an artifactual curvilinear relation to (A + B) overall accuracy, with the largest (A - B) scores occurring at about 50% (A + B) overall accuracy for a dichotomously scored free-response task. Two possible solutions are (a) to convert Task B scores to residualized scores, using the regression of Task B scores on Task A scores as determined for normal subjects; or (b) to titrate overall (A + B) accuracy of each subject to a constant level by manipulating a variable.

Cognition↗
PubMed1988

Extrapyramidal and other neurologic manifestations associated with carbon disulfide fumigant exposure.

Three groups of pesticide-exposed grain workers from three different work facilities experienced chronic central and peripheral nervous system dysfunction that appeared to be exposure related. The grain inspectors, malt laboratory workers, and grain elevator workers displayed higher prevalence rates of atypical parkinsonism, cerebellar signs, hearing loss, and sensory changes than would be expected in a nonneurologic control population. The 21 self-selected patients included in this report exhibited cogwheel rigidity in 80% (17/21), decreased associated movements in 71% (15/21), distal sensory shading in 62% (13/21), intention tremulousness in 52% (11/21), resting tremulousness in 48% (10/21), and nerve conduction abnormalities in 44% (7/16). Carbon disulfide, a major component of the fumigant mixtures used, has been associated in the rayon industry, since the 1930s, with similar neurologic symptoms.

Adult↗
PubMed1987

The measurement of handedness.

A handedness scale consisting of 13 questionnaire items selected from those of D. Raczkowski, J. W. Kalat, and R. Nebes (1974, Neuropsychologia, 12, 43-47) was found to have high internal consistency for both males and females (coefficient alpha = .96 for both sexes), high test-retest reliability (r = .97 for males and .96 for females), and a correlation of .83 with a behavioral measure of handedness. Males exhibited more nonfamilial, but not familial, left-handedness than did females. Self-description as strongly right-handed or as strongly left-handed predicted questionnaire handedness categorization better than did hand used for writing.

Adult↗
PubMed1987

Cognitive slippage and depression in hypothetically psychosis-prone college students.

Subjects who scored deviantly high on the combined Perceptual Aberration-Magical Ideation (Per-Mag) Scale and subjects who scored low on the scale were compared on two putative measures of cognitive slippage--a continued word association task and a task of referential communication. The Per-Mag subjects performed more deviantly than did the control subjects on both tasks, but those Per-Mag subjects who also scored above the mean on the General Behavior Inventory (GBI) depression subscale were most deviant. The Per-Mag Scale and the GBI are recommended for concurrent use in mass screening to identify a group of individuals who exhibit signs of cognitive slippage and who may, therefore, be at risk for the development of severe psychopathology.

Depressive Disorder↗