Biomedical subjects

K Hamsher

Publications and source records attributed to K Hamsher.

6 recordsLinked to original sources

PubMed1992

Visuospatial judgment and right hemisphere disease.

The performances of patients with stroke-produced unilateral hemispheric lesions on a test requiring the identification of lines were examined in the light of a recent report that contradicted previous observations. The study confirmed the results of earlier studies that patients with lesions of the right hemisphere show a remarkably high frequency of defective performances while those with lesions of the left hemisphere do not. Possible reasons for findings that deviate from this rule are discussed.

Aphasia↗

PubMed1991

Hemisphere asymmetry in decision making abilities. An experimental study in unilateral brain damage.

Thirty control subjects and 60 unilateral brain-damaged patients, 30 with left hemisphere (LH) damage and 30 with right hemisphere (RH) disease, underwent a disjunctive 4-choice reaction time study. Speed of reaction (as defined by the reciprocal of reaction time (RT), movement time (MT) and total response time (TRT] and accuracy of response (as represented by the sum of errors in selecting the correct response key) were investigated comparatively as a function of side of lesion and of performance on Raven's Coloured Progressive Matrices (PM47). In contrast to movement speed (1/MT), reaction speed (1/RT) as well as total response speed (1/TRT) showed a lesion effect independent of side of damage. Conversely, accuracy was differentially impaired, LH damage being associated with a significantly higher number of errors. Speed and accuracy had different relationships with the performance on the PM47 in the two hemisphere groups. Speed was affected in parallel with changes in PM47 performance both in the LH and in RH groups, whereas accuracy was altered only in LH patients. It was concluded that speed of motor reaction is affected by unilateral brain lesions irrespective of their side, whereas decision making processes, as expressed by accuracy of response, seem to be specifically impaired by LH damage.

Attention↗

PubMed1991

Constructional praxis performance of Japanese and American, normal and brain-damaged patients.

Numerous studies have suggested population differences between Japanese and Americans concerning various cognitive functions. Transcultural differences in spatial reasoning, language, and dominance for emotional expression raise important questions concerning current conceptions of hemispheric cerebral dominance for cognitive functioning. If cultural differences in cognition exist, learning may play a greater role in determining laleralizalion of cognitive functions than is presently accepted. To investigate these issues, we initiated two collaborative studies comparing Japanese with American normals and brain-damaged patients on the Three-Dimensional Constructional Praxis Test. In normal subjects, there were no significant differences between the two cultures in the distribution of visuoconstructive ability. In patients with brain damage, the effects of unilateral brain lesions and their neuropsychological consequences on visuoconstructive ability were similar in both cultures. Thus, there are no apparent differences between the Japanese and American peoples in visuoconstructive abilities, or in the underlying cerebral organization of skills required to execute these functions.

Journal Article↗

PubMed1983

Mental status examination in Alzheimer's disease. The neuropsychologist's role.

The neuropsychologic consultant can offer an objective and comprehensive method of documenting the mental status of patients being evaluated for dementia. The neurobehavioral examination is an extension and elaboration of the bedside mental status examination, with added methods of controlling for various background factors that can influence performance on cognitive testing. In dementia, the cognitive findings appear to have a close association with the underlying neuropathologic changes and mortality. This makes the neurobehavioral examination useful in differentiating dementia from other neurologic and psychiatric conditions when the clinical diagnosis is uncertain.

Aged↗

PubMed1978

Spontaneous recovery in rabbit eyelid conditioning.

Spontaneous recovery of the classically conditioned rabbit eyelid response increased in a negatively accelerated function with an increase of postextinction rest from .17 to 24 hr. The data were obtained from six groups of male New Zealand rabbits which received an extinction session separated by rest intervals of varying duration from a spontaneous recovery test.

Animals↗

PubMed1977

The reliability of reaction time determinations.

The reliability of simple and two-choice reaction time (RT) as a function of number of trials and measure of central tendency was examined. It was found that, within the particular conditions of the study, 18 trials were sufficient to obtain a highl reliable determination of simple RT but 30 trials were required for a highly reliable determination of two-choice RT. The selection of measure of central tendency was not related to degree of reliability.

Adult↗