Effects of handedness and sex on the morphology of the corpus callosum: a study with brain magnetic resonance imaging.
ABSTRACT In view of conflicting data in the existing literature, we examined 53 normal subjects using a handedness questionnaire and callosal area measurements obtained from midsagittal MRI images. The callosum was found to be significantly larger in nonconsistent right-handers (NCRH), especially in its anterior half and especially for males. A significant hand x sex interaction, favoring consistent right-handed (CRH) females, was also found for the posterior midbody, a region known to house interhemispheric fibers connecting the right and left posterior association cortices. These results (1) confirm Witelson's (1985) first findings on postmortem specimens; (2) validate a dichotomy between CRH and NCRH rather than simply considering the writing hand, as was the case in most other similar studies; and (3) suggest that at least two different sex-related--probably hormonal--factors may be acting during the callosal development, one explaining the larger anterior half in NCRH males and the other the larger posterior midbody in CRH females.
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ABSTRACT: Two methodological variants of Kahneman and Tversky's Asian disease scenario were investigated. One variant involved replacing the “all-or-none” outcome scenarios of the risky choice with “most-or-some” scenario outcomes, and the second variant involved replacing the negative domain of lives lost with a positive domain of jobs created. In addition, the effects of strength of handedness, a variable related to individual differences in risk perception, were examined. Results indicated that standard framing effects were obtained across both domains, with a decrease in risky choice under the gain domain. Scenario type also interacted with handedness, such that the all-or-none scenario yielded framing effects for consistent (strong)-handers only, whereas the most-or-some scenario yielded framing effects for inconsistent (mixed)-handers only (consistent-handers are those who use the same hand exclusively for almost all activities). These results demonstrate that framing effects are strongly influenced by the presence versus absence of extreme/absolute outcomes and that individuals (in this case, decision makers with varying degrees of handedness strength) are differentially sensitive to different pieces of information.Journal of Behavioral Decision Making 01/2014; 27(4):378-385. DOI:10.1002/bdm.1815 · 2.84 Impact Factor
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ABSTRACT: ABSTRACT The authors' aim was to compare interhemispheric transfer time between 2 groups: highly skilled sportsmen and control subjects. Left- and right-handed individuals were included in the study. The Poffenberger paradigm was used to measure the crossed-uncrossed difference, representing the time to transfer information from one hemisphere to the other. No difference in laterality was found, but the results revealed a greater crossed-uncrossed difference in the skilled sportsmen than in the controls. The authors suggest that this may be due to more highly developed within-hemisphere integration of inputs and outputs, at the expense of cross-hemisphere integration.Journal of Motor Behavior 10/2012; 44(5):373-7. DOI:10.1080/00222895.2012.724476 · 1.41 Impact Factor
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ABSTRACT: We used diffusion tensor imaging to assess callosal morphology in 35 pairs of monozygotic twins, of which 17 pairs were concordant for handedness and 18 pairs were discordant for handedness. Functional hemispheric language dominance was established for each twin member using fMRI, resulting in 26 twin pairs concordant and 9 twin pairs discordant for language dominance. On the basis of genetic models of handedness and language dominance, which assume one "right shift" (RS) gene with two alleles, an RS+ allele biasing toward right-handedness and left cerebral language dominance and an RS- allele leaving both asymmetries to chance, all twins were classified according to their putative genotypes, and the possible effects of the gene on callosal morphology was assessed. Whereas callosal size was under a high genetic control that was independent of handedness and language dominance, twin pairs with a high probability of carrying the putative RS+ allele showed a connectivity pattern characterized by a genetically controlled, low anisotropic diffusion over the whole corpus callosum. In contrast, the high connectivity pattern exhibited by twin pairs more likely to lack the RS+ allele was under significantly less genetic influence. The data suggest that handedness and hemispheric dominance for speech production might be at least partly dependent on genetically controlled processes of axonal pruning in the corpus callosum.Journal of Cognitive Neuroscience 07/2012; 24(10):1971-82. DOI:10.1162/jocn_a_00267 · 4.69 Impact Factor