The Relationship Between Handedness And Brain Asymmetry:A Multimodal Brain Imaging Research

In human biology,handedness is a better,faster,or more precise performance or individual preference for use of a hand,known as the dominant hand,and perhaps is the most overt reflection of lateralization of the central nervous system in humans.In brain imaging studies,handedness is often associated with asymmetries in brain anatomical morphology and function.Recent findings shown that the brain regions related to handedness in anatomical morphology were mainly located at the subcortical tissues,which support many advanced cognitive functions,and language network,which mainly includes frontal and temporal lobe.There were also correlations between handedness and white matter fiber bundles,such as corpus callosum,arcuate fascile and superior longitudinal fascile,in anatomical morphology and microstructure properties.The relationship between cerebral lateralization of language and handedness has been studied for years,and the spontaneous activity of this network were also closely associated with handedness.By summarizing previous studies,the author found that handedness seemed to be more correlated with the asymmetries of brain function than with brain anatomical morphology.In addition to this,most of studies have only concentrated on exploring the brain anatomic foundation or the functional mechanism underlying handedness,and few studies attempted to make a prediction framework based on these brain characteristics underlying handedness.Therefore,in order to test this hypothesis and fill in the deficiencies of previous studies,this study paid attention to the influence of handedness to the brain asymmetry,both in brain structure and functional level,and attempted to explain our results in a unified framework.In order to validate the reliability of our results,we employed these brain features associated with handedness to predict individual hand preference of the Cambridge Centre for Ageing and Neuroscience(Cam-CAN)samples.As a consequence,this study carried out four sub-studies to investigate the connection between handedness and the asymmetry of brain anatomical morphology and function,and predict individual handedness coefficient by employing these significant characteristics based on handedness.The focus of study 1 to 3 was to explore the brain anatomical morphological basis and functional activity mechanism of handedness,and extracted the corresponding brain characteristics to build a prediction model,and completed the prediction of individual handedness coefficient in study 4.In detail,study 1 attempted to investigate the association between handedness and the asymmetry of gray matter volume,and the results shown that there was a significant correlation between handedness and the asymmetry of the gray matter volume in thalamus,and this correlation can be explained based on the function of thalamus in supporting language and motor.Study 2 aimed to identify the connection between handedness and brain asymmetry of white matter fiber microstructure,and the results suggested that handedness was negatively related with the asymmetry of the fractional anisotropy in splenium of corpus callosum,which can be further clarified in the link between handedness and language lateralization.Given the relationship between the handedness and language lateralization,in the third study,the regions within language functional network were selected as the seeds and seedbased voxel-wise resting state functional connectivity were calculated,and the results indicated that the individual hand preference was significantly correlated with the asymmetry of the functional connectivity between bilateral triangular part of inferior frontal gyrus and left insular,left middle occipital gyrus,and left supplemental motor area,between bilateral insular and left middle temporal gyrus and left medial superior frontal gyrus,between bilateral superior temporal gyrus and left middle occipital gyrus,between bilateral middle frontal gyrus and left fusiform and left postcentral gyrus,between bilateral supplemental motor area and left middle frontal gyrus.In the last study,the corresponding brain asymmetric features were extracted to build a model,and the prediction of the individual handedness index was completed.After matching age,gender and handedness index between left-and right-handers,this study included 49 left-handers and the equal number of right-handers of Cam-CAN dataset.Study 4 employed the backward stepwise regression analysis method to build the prediction model.This method can eliminate the independent variables that don't have significant prediction effect,one by one,and re-evaluate the model so that only those variables that can significantly predict the dependent variable are included in the last optimal model.We found that there were three asymmetric features in the model that can significantly predict the individual handedness index variation of 11.6%,that are,the asymmetry of functional connectivity between bilateral triangular part of inferior frontal gyrus and left insula,between bilateral insula and left medial superior frontal gyrus,between bilateral middle frontal gyrus and left postcentral gyrus,indicating that the relationship between handedness and brain asymmetry is mainly manifested in the brain function,which is consistent with the research hypothesis.It also suggested that the joint effects of language and motor function system,genetic and environmental factors may have a stronger explanatory power for handedness.In conclusion,this study employed multimodal brain imaging data to examine the correlation between handedness and brain asymmetry in morphology and function level.And then we used these asymmetric characteristics to predict the individual handedness index of Cam-CAN dataset,which improves the overall reliability of the total study.Future exploration could expand the sample size,use the multimodal brain imaging data,and employ the advanced analysis methods to investigate the mechanism of the brain asymmetry of handedness.In short,this study comprehensively investigated the anatomical basis and functional mechanism of the brain of handedness,and combined these brain characteristics to predict the individual handedness coefficient of other dataset,which filled in the shortcomings of previous research,and dissected the association between handedness and the brain asymmetry from an evolutionary perspective.This research provided further evidence for a deep understanding of the brain mechanism of handedness,and also offered reference for prediction study and data mining on handedness based on multi-modal imaging data in future.