Search

It seems to me that one of the crucial facts disclosed by the lead paper (which is well organized and comprehensive) is that there remains a lack of basic information and/or hard data on some specific aspects of the subject-matter. That is to say, there seem to be many stones left unturned as yet to be able to solve the ‘puzzle’, i.e. the phenomenon of better linguistic production of writing in the right dominant hemiplegic limb through the use of prosthesis relative to that in the unaffected left hand. The following are some examples of the types of informationdata that could be obtained in future studies to help develop possible explanatory theories for this most intriguing phenomenon.

Recovery curve of the Hoffmann reflex from the left and right sides was studied in lightly anesthetized cats before and after spinalization. According to the differences in the H-reflex recovery curves from the left and right lateral gastrocnemiussoleus nerves, three populations of intact animals were found: right dominant with higher recovery curve on the right side (31.8%), left dominant with higher recovery curve on the left side (36.4%), and ambilateral with no dominance (31.8%). After spinalization the dominance remained the same in the two first groups and dominance appeared in 5 out of the 7 cats of the last group. These results provide evidence for a bilateral asymmetry of alpha motoneuron excitability in cats, which can be used as a model to study the possible mechanisms of spinal motor asymmetry.

In order to determine the normal size of various branches of the coronary arteries and to clarify the etiological factors that determine the dominant patterns of coronary arteries (dominance) and the relationship between the growth of the coronary arteries and the ventricles, the caliber and the distribution of major coronary arterial branches were measured by selective coronary arteriography in 41 cases with normal hearts and 49 cases with congential heart disease. In normal hearts, the incidences of right dominant(R), balanced(B) and left dominant(L) types were 78%, 15% adn 7%, respectively. In congenital heart disease, the incidences of R, B and L types in right ventricular loading hearts (RV group) were 94%, 0% and 6%, respectively and those in left ventricular loading hearts (LV group) were 58%, 27% and 15%, respectively. The ratios of left main trunk and proximal right corornary in size (LMT/RCA ratio) in RV group weremuch smaller and LMT/RCA ratios in RV group were much larger than those in normal hearts. these results indicated that in the different types of heart anomalies the loading of pressure and volume to the ventricles varies in grade, and subsequently induced the hypertrophy of the loaded parts. It was thought that the resultant hypertrophy also affected the growth and dominance of the coronary arteries.

A stratified random sample of 153 right-dominant children (6 to 9 years of age) with normal or above intelligence was selected to study the development of hand strength, and the quality and duration of prone extension as a function of age, sex, height, and weight of the child. The Jamar hand dynamometer was used to measure hand strength, and a new scale for rating the quality of prone extension was presented. Both right- and left-hand strength increased monotonically with age, with the right being significantly higher than the left. Duration of prone extension increased monotonically with age, but quality of prone extension did not correlate with age. Sex differences were found only on the variable left-hand strength (males greater than females). Hand strength demonstrated weak correlation with duration of prone extension. Both height and weight exhibited strong positive correlations with hand strength, weaker positive correlations with duration of prone extension, and no correlation with quality of prone extension. The results suggest hand strength can be an index of normal development, and children ages 6 to 9 can attain the prone extension position; however, the meaning of duration greater than 30 seconds needs to be researched further.

The present study addressed the question of Levy's (1974, Psychobiological implications of bilateral assymetry. In S. Dimond & J. G. Beaumont, Hemispheric function in the human brain , NY: Halstead. Pp. 121–183.) proposal that left handers would have lowered spatial skills relative to verbal skills. In the first part of the study, performance on the PMA (visuospatial subtest) and WAIS Block Design subtest were compared between right and left handed high school and college samples. No support could be found for deficient visuo-spatial performance in the left handers. In the second part of the experiment, no relative impairment of visuospatial skills was found when subjects were classified into predicted speech dominance groups on the basis of a dichotic listening task and/or a visual half-field task. An extreme groups comparison of the most left dominant and most right dominant groups again yielded no significant differences in visuo-spatial performance. Finally, the relationship between degree of speech lateralization and visuo-spatial skills was examined. Only partial support for differences in cerebral organization for speech in left handers was found in the college sample.

On a Cognitive Laterality Battery designed to measure functioning of the left and right cerebral hemisphere, dyslexic children were consistently better on tests of right hemisphere function than on tests of left. Surprisingly, most (90%) of the first degree family members of dyslexics also had the same, right dominant profile, even though most of them claimed never to have a reading problem. In a series of reading tests where letters were flashed one at a time, the dyslexics were selectively impaired on the test requiring sequential analysis. Since their reading scores were correlated with overall left and right hemisphere performance and with each hemisphere separately, it was hypothesized that dyslexics were “locked” into a right hemisphere mode of processing which governed all their cognitive activity.

A patient had right hemiparesis since infancy. At age 31, she had recurrent right focal motor and sensory seizures. In prolonged focal seizures, she could not speak but retained most other language-related functions. Intra-carotid cerebral amytal testing demonstrated right hemisphere speech. Left intra-carotid amytal injection stopped a typical attack. Complete section of the corpus callosum abolished the aphemic episodes and reduced the frequency and intensity of the focal seizures. Focal seizure activity in the left nondominant hemisphere appears to have caused restricted functional disturbance in the right dominant hemisphere.