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At least 901 records · Page 50Linked to original sources
PubMed2001

Fetal handedness and head position preference: a developmental study.

Hand-head contacts were observed by means of serial ultrasound recordings in 10 healthy fetuses from 12 to 38 weeks of gestational age. Contacts were distinguished as being unimanual or bimanual, and if unimanual, whether they were made with the right or left hand. Both types of contact and ones made unimanually with the right or left hand were identified at each age as to whether they were associated with a preferential head position. A strong unimanual bias was evident at each age except for Week 36. At this age, there was a bimanual bias. Unimanual contacts did not develop a lateralized preference, and neither type of contact established a stable relationship with head position. Furthermore, there was no evidence to support the suggestion that hand contact and head position codevelop to form a preferred ipsilateral synergy. Findings are discussed relative to contradictory evidence from other fetal and neonatal studies.

Choice Behavior↗
PubMed2006

Plasticity in the development of handedness: evidence from normal development and early asymmetric brain injury.

Previous research revealed that shifting patterns of hand preference in the first year of life are linked to infants' sensory-motor experiences as they learn to sit, creep, and walk. In this report, we examine whether new and different forms of locomotion and sensory-motor experiences similarly contribute to alter patterns of hand preference in early development. We examined the cases of three infants with unique developmental histories. Two infants adopted distinctive forms of locomotion in lieu of typical hands-and-knees crawling. One infant scooted using both hands and legs in a coupled fashion, while the other infant performed an asymmetrical, left-biased belly-crawl using only one arm to drag his body. The third infant suffered damage to his left-brain hemisphere shortly after birth and received intense physical therapy to his right arm as a result of it. We followed all three infants on a weekly basis and tracked changes in their reaching behavior, mode of locomotion, and postural achievements. The two infants with unique locomotor patterns displayed changes in hand preference that reciprocated the arm patterns that they used during locomotion. The infant who coupled his body for scooting began to reach bimanually, while the infant who adopted the left-biased belly-crawl developed a strong unimanual, right-hand, preference. The infant with left-hemisphere damage initially displayed a right-hand preference, then a temporary decline in preferred hand use as he began to cruise and walk, and ultimately resumed a right-hand preference in the 2nd year of life. This data is consistent with previous work showing that the development of hand preference in the 1st year of life is highly malleable and sensitive to a variety of new sensory-motor experiences.

Age Factors↗
PubMed1993

The measurement of handedness by preference and performance tests.

Hand preference and hand proficiency were compared on 50 male subjects (30 self-classified left-handers and 20 self-classified right-handers) according to their responses to a 20 item questionnaire and their performances on a handwriting and a grip-strength task. Performance differences between the two sides for each group were not related to overall preference assessments but were positively associated with hand preferences on corresponding questionnaire items. Distributions of the performance differences between the two sides for the right- and left-handers were well separated for handwriting but completely overlapped for grip strength. Significant correlations between the performances on each side were recorded on both tasks. The results stress the importance of using the same criteria in making preference vs. performance comparisons and highlight the need to recognize and control the influence of previous training or experience.

Adolescent↗
PubMed1994

If you can replicate the handedness-immune disorder effect, the more power to you.

Bryden, McManus, and Bulman-Fleming's (1994) meta-analysis of studies examining the Geschwind-Behan-Galaburda hypothesis indicates that the original data set supports the hypothesis significantly more than the body of replication attempts. We present data on 2256 subjects that clearly fail to support the hypothesis and describe practical and statistical reasons suggesting why the original data cannot be easily replicated. A power analysis suggests that to find the effect in a general sample, one should plan to have 17,000 to 40,000 subjects.

Child↗
PubMed1998

Handedness and sex differences in intelligence: evidence from the medical college admission test.

Our analysis of Medical College Admission Test subtest scores by writing hand preference and sex suggests that (a) right hemispheric dominance is associated with intellectual giftedness in verbal reasoning (left-handers obtained higher scores on the verbal reasoning test and were overrepresented in the upper tail of the distribution), (b) different patterns of brain lateralization are associated with different subcomponents of cognition (right-handers scored higher, on average, on the writing test and were overrepresented in the upper tail of the distribution), and (c) men generally score higher than women on tests of scientific knowledge (the most striking differences between men and women were on the biological and physical science tests).

Adult↗
PubMedDate not supplied

The influence of handedness on profile and line drawing directionality in children, young, and older normal adults.

One hundred twenty-two normal subjects--children, young and older adults (77 right-handers and 45 left-handers)--performed two drawing tasks in order to study their directionality trends. The first task consisted of drawing the profile of a face and in the second task subjects had to link two points in order to draw a line. The analysis of the drawing directionality revealed a significant effect of the age when right-handers drew profiles whereas this effect reached significance in left-handed subjects only when drawing lines. Left- and right-handers' performances across the two tasks were found to significantly differ. Results are discussed in terms of hemispheric and environmental factors.

Adult↗
PubMed1998

Abnormal callosal morphology in male adult dyslexics: relationships to handedness and phonological abilities.

The classical notion that developmental dyslexia may somehow relate to impaired communication between hemispheres has not yet received convincing support. Sixteen dyslexic adults and 12 controls received a high resolution brain MRI scan for morphometric study of the corpus callosum. Automatized measurements of callosal area and calculation of indices defining the general morphology of the callosal mid-surface were performed. Each participant received global intelligence and reading achievement evaluation; dyslexics were further proposed specific neuropsychological tests specially designed to explore the mechanisms of reading impairment. It just appears from the group comparisons (1) that the dyslexics' corpus callosum displays a more circular and evenly thicker general shape, and (2) that the midsagittal surface is on the average larger than in controls, in particular in the isthmus. Moreover, the different morphometric characteristics of the dyslexic brain correlated with the degree of impairment on various tests exploring phonological abilities. In vivo morphometry of the corpus callosum may provide valuable hints for understanding developmental learning disorders and their consequences in adults.

Adolescent↗
PubMed2000

Mirror writing and handedness.

It has been reported that left-handed subjects are better able to write in mirror-reversed script than right-handers (Tankle & Heilman, 1983). Vaid and Stiles Davis (1989) conducted studies which led them to contradict the supposed superiority of left-handers in this area. In these studies, left as well as right-handed subjects were examined under normal- and mirror-writing conditions. Both examinations included the analysis of writing time and the accuracy of mirror writing (error rates). Using a digitizing tablet, we examined normal- and mirror-writing performance of left-handers, right-handers, and left-handed subjects who habitually write with their right hand. Our results support the finding of Tankle and Heilman (1983) that left-handers perform better in mirror-writing tasks.

Adult↗
PubMed1993

Lateralisation of speech centre in left-handedness due to cerebral and extracerebral lesions.

This report is based on a study of a small sample of five patients who were initially right-handed and became left-handed due to loss of function in the right arm after extracerebral causes such as polio or injury. Carotid amytal tests in these patients showed that all of them still had the speech centre in the left hemisphere. As expected, lateralised neuropsychological brain function tests showed no significant differences between right and left brain. In infantile right hemiplegia due to atrophic left brain lesions, the speech centre had shifted to right side in 10 out of 15 patients. Neuropsychological tests showed sparing and protection of dominant left brain functions.

Adolescent↗
PubMed1996

Response times and handedness in simple reaction-time tasks.

The anticipatory (preparatory) cerebral events in simple reaction-time tasks may depend on the ability of a subject to predict accurately the time of occurrence of the stimulus requiring a particular response. In order to examine this hypothesis, we recorded cerebral and muscle responses in two different conditions, each involving three simple reaction-time tasks. Auditory tones were presented either regularly (i.e., predictably) or irregularly and subjects were required to respond to each tone with left hand, right hand or both hands in different runs. Responses were simultaneously averaged both backward and forward from the response (response-synchronized) and forward from the stimulus (stimulus-synchronized). Response-synchronized cerebral potentials to the regular tones were characterized by a slow negative shift, the bereitschaftspotential (BP), that began prior to stimulus onset and whose terminal phase was characterized by a small, higher frequency, negative shift (HFNS). By contrast, response-synchronized cerebral potentials to the irregular tones for both groups did not contain a BP, but a more conspicuous HFNS that began after stimulus onset. Both the response time and the latency of the N1 sensory-related component of the cerebral evoked potential recorded in the stimulus-synchronized averages (which aligns with HFNS) were delayed in the irregular condition. These findings suggest that, for both right- and left-handed subjects, the BP is not required for voluntary movement, and that anticipatory cerebral activity, as reflected by the BP, represents not only a preparation to make a particular response but also a preparation to process the stimulus.

Adult↗
PubMed1982

Determination of the handedness of the crossbridge helix of Limulus thick filaments.

Thick filaments, isolated in their long conformation from unstimulated Limulus telson muscles, were shadowed with platinum or platinum-carbon and examined using electron microscopy and optical diffraction techniques. All filaments showed evidence of a right-handed surface helix, which had a major repeat at approx. 43 nm. In fortuitously oriented specimens the subunits, presumably crossbridges, which comprised the helical strands were clearly delineated. Optical transforms obtained from images of shadowed filaments confirmed the helical repeat at approx. 43 nm and could be readily interpreted as patterns expected from a one-surface view of the four-stranded filament structure we have previously reported. The striking resemblance between optically filtered images of shadowed filaments and the computed reconstruction of the one-surface filament further confirm our model for the myosin lattice of the Limulus thick filament.

Animals↗