Biomedical subjects
D Kimura
Publications and source records attributed to D Kimura.
The relationship between testosterone levels and cognitive ability patterns.
The cognitive performance of normal men and women was studied, grouped according to whether the subjects had relatively high or low salivary testosterone (T) concentrations. Men with lower T performed better than other groups on measures of spatial/mathematical ability, tasks at which men normally excel. Women with high T scored higher than low-T women on these same measures. T concentrations did not relate significantly to scores on tests that usually favor women or that do not typically show a sex difference. These results support suggestions of a nonlinear relationship between T concentrations and spatial ability, and demonstrate some task specificity in this respect.
Evidence for subgroups of adextrals based on speech lateralization and cognitive patterns.
Some non-right-handers may prefer the left hand by virtue of well-organized or high levels of spatial ability, vested primarily in the right hemisphere, rather than as a result of anomalous speech representation. This study tested the hypothesis that adextral (left-handed or ambidextrous) individuals with high spatial ability might have cerebral speech lateralization patterns similar to dextrals. Paper-and-pencil tests of various cognitive abilities, a verbal dichotic listening task, and a handedness inventory were administered to two groups (science or non-science students) of adextral and dextral subjects. The science group had predictably higher spatial ability than the non-science group. Adextral science students were as lateralized on dichotic listening, and had equal spatial ability, compared to dextral science students. Adextral non-science males were less lateralized and had (unexpectedly) poorer spatial ability than dextral non-science males. Thus in adextrals, variations in ability patterns may be related to variations in speech lateralization.
Right-hand superiority for throwing but not for intercepting.
In humans, the organization of movements performed by both upper limbs, relies significantly on a left hemisphere "praxis" system that also subsumes speech function. Right hand preference may also be an expression of this left hemisphere dependence, arising from the preferential connections of the right hand to the left hemisphere. Consequently, a manual task that maximizes the spatial complexity of a target (presumably engaging right hemisphere mechanisms), while concurrently minimizing motor-programming demands, was expected to yield a diminished disparity in preference and performance between the hands. Left and right hand accuracy were measured independently for two motor tasks in 48 normal right-handed university students. In the first task, darts were thrown overhand at a stationary target. For the second task, subjects were asked to use the open hand to block (but not catch) projectiles launched at varying trajectories and velocities. ANOVA yielded a significant Hand x Task interaction, in which the left hand did not differ from the right hand in intercepting ability, but was significantly less accurate than the right hand for throwing. A sex difference favouring males was found for both tasks; this difference was not reducible to differences in physique or athleticism.
The relation between oral movement control and speech.
A large series of neurological patients, selected solely on the basis that they had damage restricted to one hemisphere of the brain, was given a variety of tests of basic speech and praxic function. Within the left-damaged group, patients were further identified as aphasic or nonaphasic, based on preexisting standard tests of aphasia. Subgroups of aphasics were studied on the basis of lesion location, rather than on the basis of aphasia type. The focus of the study was the relation between the production of speech and nonspeech oral movements, particularly across anterior and posterior lesions. Reproduction of single nonverbal oral movements and of single isolated speech sounds was found to be very highly correlated, and both depended selectively on the left anterior region of the brain. This same region was critically important for rapid repeated articulation of a syllable, suggesting that it mediates control at some "unit" level of movement, in a phenomenological sense, for both speech and nonspeech movements. Other "speech" regions in the left hemisphere appeared to be dispensable for the production of single oral movements, whether these were verbal or nonverbal movements. However, for most aphasic patients, an area in the left posterior region was inferred to be essential for production of multiple oral movements, whether nonverbal or verbal, suggesting a critical role in the accurate selection of movements. Within the posterior region, there was further differentiation for multisyllabic speech into a parietal system, which appeared to mediate primarily praxic function, and a temporal system, which appeared to mediate verbal-echolalic function. Aphasias from anterior and posterior lesions resembled "Broca's" and "Wernicke's" aphasia only insofar as they differed in fluency, with anterior aphasics clearly less fluent. Tests of speech comprehension did not differentiate the groups. It is suggested that classifying aphasic patients via lesion location rather than aphasic typology might yield a view of functional subsystems different from those commonly accepted.
Neuropsychological improvement versus practice effect following unilateral carotid endarterectomy in patients without stroke.
Patients who were admitted to hospital for a recent transient ischemic attack were entered into one of three groups based on medical and surgical characteristics; those with an abnormal neurological examination or a focal abnormality on CT Scan were omitted from the study. The two surgical groups (12 patients each) underwent either a left or right endarterectomy for a symptomatic atheroma of the ipsilateral carotid artery. The control group consisted of 12 patients who either demonstrated minor or nonexistent carotid abnormalities or a TIA distribution that was contralateral to what would otherwise have been a surgically treatable lesion. Patients were tested before surgery and again 6-8 weeks later with the WAIS, WMS, and other neuropsychological measures. Significant improvement on some measures at follow-up was strictly equivalent across all groups and was attributed to practice effects.
Reciprocal effects of hormonal fluctuations on human motor and perceptual-spatial skills.
Normal adult women showed systematic performance fluctuations across the menstrual cycle on several motor and perceptual tests that typically yield sex differences in performance. The midluteal phase, characterized by high levels of estradiol and progesterone, was associated with improved performance on tests of speeded motor coordination and impaired performance on a perceptual-spatial test, relative to performance during menses. Variations in gonadal steroid levels may contribute substantially to the sex differences reported in human cognitive and motor skills.
Hand movement asymmetry during speech: no effect of speaking topic.
Right-handed subjects were videotaped as they spoke on verbal, spatial and neutral topics and the frequencies of their spontaneous hand movements were analyzed. Although subjects made more free movement gestures during the spatial topics than during the other topics, there was a consistent level of right hand preference for free movements across topics. Self-touching movements showed no hand preference in any topic. The results suggest that free movements are generated by a left-hemisphere motor control system which exerts consistently greater influence over the right than the left hand regardless of the source of processing preceding activation of this system.
Attentional and perseverative impairment in two cases of familial fatal parkinsonism with cortical sparing.
The neuropsychological findings in twin brothers with familial fatal Parkinsonism are reported. Post-mortem examination had shown extensive pathology in basal ganglia and brainstem, but not in the cerebral cortex. Although both showed average intelligence three months prior to death, they had impairment on a sorting task and in serial attention span. Some possible neural mechanisms are discussed.
Impairment of nonverbal oral movements in aphasia.
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Acquisition of a motor skill after left-hemisphere damage.
Specialization of function in the left hemisphere of man, as compared with the right, was studied with special reference to the nature of the impairments seen after left-hemisphere damage. Patients with unilateral lesions of the left or the right hemisphere were compared in the acquisition and subsequent performance of a manual skill requiring several hand movements. Patients with left-hemisphere damage were further subdivided into aphasic and non-aphasic groups. Patients with left-hemisphere damage were further subdivided into aphasic and non-aphasic groups. Patients with left-hemisphere damage, whether aphasic or not, were impaired in the acquisition of the task, relative to patients with right hemisphere damage, although aphasics were most severely impaired. Analysis of the errors made during acquisition indicated that perseverative errors and unique errors (unrelated movements) differentiated the left and right groups, but that sequencing errors did not. It was concluded that a major function of the left hemisphere is the control of changes in limb or articulatory posture, and that its complex verbal and praxic functions are derived from such control.
Intrahemispheric interaction between speaking and sequential manual activity.
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Impairment of nonlinguistic hand movements in a deaf aphasic.
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Motor functions of the left hemisphere.
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Manual activity during speaking. I. Right-handers.
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Manual activity during speaking. II. Left-handers.
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The asymmetry of the human brain.
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