When more is less: Associations between corpus callosum size and handedness lateralization

Department of Neurology, UCLA School of Medicine, Los Angeles, CA 90095-7334, USA.
NeuroImage (Impact Factor: 6.36). 08/2010; 52(1):43-9. DOI: 10.1016/j.neuroimage.2010.04.016
Source: PubMed


Although not consistently replicated, a substantial number of studies suggest that left-handers have larger callosal regions than right-handers. We challenge this notion and propose that callosal size is not linked to left-handedness or right-handedness per se but to the degree of handedness lateralization. To test this hypothesis, we investigated the thickness of the corpus callosum in a large data set (n=361). We analyzed the correlations between callosal thickness and the degree of handedness lateralization in 324 right-handers and 37 left-handers at 100 equidistant points across the corpus callosum. We revealed significant negative correlations within the anterior and posterior midbody suggesting that larger callosal dimensions in these regions are associated with a weaker handedness lateralization. Significant positive correlations were completely absent. In addition, we compared callosal thickness between moderately lateralized left-handers (n=37) and three equally sized groups (n=37) of right-handers (strongly, moderately, and weakly lateralized). The outcomes of these group analyses confirmed the negative association between callosal size and handedness lateralization, although callosal differences between right- and left-handers did not reach statistical significance. This suggests that callosal differences are rather small, if examined as a dichotomy between two handedness groups. Future studies will expand this line of research by increasing the number of left-handers to boost statistical power and by combining macro- and microstructural, as well as functional and behavioral measurements to identify the biological mechanisms linking callosal morphology and handedness lateralization.

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    • "l group contrast t ' s ≤1 ) . Table 2 provides the means , by group , for intracranial volume and corpus callosum area . As indicated by the t - test results in Table 2 , the hand groups did not differ in overall brain size nor in any corpus callosum volume measurement . In order to more precisely compare our corpus callo - sum results to those of Luders et al . ( 2010 ) , we also computed correlations between the absolute value of the hand preference score and the corpus cal - losum measurements . No significant correlations were obtained for total cal - losal volume , nor for any callosal subregion ( all r ' s < . 10 ) . Table 3 includes the global asymmetry means by group , and relevant stat - isti"
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    ABSTRACT: Various cognitive differences have been reported between consistent and weak handers, but little is known about the neurobiological factors that may be associated with this distinction. The current study examined cortical structural lateralization and corpus callosum volume in a large, well-matched sample of young adults (N = 164) to explore potential neurostructural bases for this hand group difference. The groups did not differ in corpus callosum volume. However, at the global hemispheric level, weak handers had reduced or absent asymmetries for grey and white matter volume, cortical surface area, thickness, and local gyrification, relative to consistent handers. Group differences were also observed for some regional hemispheric asymmetries, the most prominent of which was reduced or absent gyrification asymmetry for weak handers in a large region surrounding the central sulcus and extending into parietal association cortex. The findings imply that variations in handedness strength are associated with differences in structural lateralization, not only in somatomotor regions, but also in areas associated with high level cognitive control of action.
    Laterality 10/2015; DOI:10.1080/1357650X.2015.1096939 · 1.13 Impact Factor
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    • "A growing body of research indicates that consistent (strong)handedness (i.e., exclusive use of the right hand for virtually all manual activities requiring fine motor control) is associated with decreased access to processes localized to the right hemisphere (RH), including episodic memory retrieval (e.g., Lyle, McCabe, & Roediger, 2008; Propper, Christman, & Phaneuf, 2005), body image representation (e.g., Christman, Bentle, & Niebauer, 2007; Niebauer, Aselage, & Schutte, 2002), and belief updating (e.g., Christman, Henning, Geers, Propper, & Niebauer, 2008; Jasper, Prothero, & Christman, 2009). This decreased access to RH processing is presumed to reflect the presence of (i) a smaller corpus callosum in strongly right-handed people (e.g., Clarke & Zaidel, 1994; Denenberg, Kertesz, & Cowell, 1991; Habib et al., 1991; Luders et al., 2010; Witelson & Goldsmith, 1991) and, subsequently, decreased RH activation in strongly righthanded people (e.g., Flor-Henry & Koles, 1982; Papousek & Schulter, 1999; Propper, Pierce, Geisler, Christman, & Bellorado, 2012). This idea that consistent (strong) right-versus inconsistent (mixed)-handedness is associated with decreased versus increased access to RH processing, respectively, has recently been extended to issues involving risk perception. "
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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 10/2014; 27(4):378-385. DOI:10.1002/bdm.1815 · 2.84 Impact Factor
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    • "One explanation for the differences in episodic memory is related to the increased collaboration between the left and right hemisphere. In support of the findings of superior episodic memory performance by weaker DH participants, studies have shown that the size of the corpus callosum is larger in weaker versus stronger DH participants (Clarke & Zaidel, 1994; Cowell, Kertesz, & Denenberg, 1993; Luders et al., 2010). Here a region, the precuneus, that has been linked to episodic memory revealed activation that was modulated by DH (Aggleton & Pearce, 2001; Binder & Desai, 2011; Binder, Desai, Graves, & Conant, 2009; Epstein, Parker, & Feiler, 2007; Vincent et al., 2006). "
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    ABSTRACT: The impact of handedness on language processing has been studied extensively and the results indicate that there is a relationship between the two variables; however, the nature of the relationship is not at all clear. In the current study we explored degree of handedness (DH) opposed to direction in a group of right-handed individuals. fMRI was used to explore the impact of DH on the sentence comprehension network. The results revealed that during sentence comprehension activation in regions linked to semantic memory (e.g., anterior temporal cortex) were modulated by DH. Also, unexpectedly the precuneus/posterior cingulate gyrus which has been linked to episodic memory was also affected by DH. These results extend those reported previously by showing that the neural architecture that supports sentence comprehension is modulated by DH. More specifically, together the results presented here support the hypothesis proposed by Townsend, Carrithers, and Bever (2001) that DH interacts with the language system and impacts the strategy used during sentence comprehension.
    Brain and Cognition 03/2014; 86C(1):98-103. DOI:10.1016/j.bandc.2014.02.002 · 2.48 Impact Factor
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