Relationship Between Speech Production And Executive Control Lateralization In Left-handers And Related Cognitive Neural Basis

Hemispheric functional lateralization is a fundamental organization principle of the human brain on a large scale,with left-lateralized language and right-lateralized executive control(visuospatial attention and response inhibition)being the two most prominent types of hemispheric lateralized cognitive functions known.Although the respective neural representations of the above cognitive functions have been explored elaborately,the relationship between the lateralization of functions and their cognitive neural basis is not yet clear.There are two opposing hypotheses about the lateralization relationship between functions: the "causal" hypothesis suggests that the lateralization of functions is interdependent and that this relationship is not specifically causal,but may also be caused by the common origin.The "statistical" hypothesis assumes that the lateralization of each function is independent of each other.To test these two hypotheses,we examined the relationship between the lateralization of speech production,visuospatial attention and response inhibition using functional magnetic resonance techniques in a left-handed group with high variability in lateralization.Both executive control functions were found to be correlated with lateralization of speech production,providing supporting evidence for the "cause and effect" hypothesis.Considering the directional and co-lateralized relationships between multiple functional specifications.Study 2 combined task-state MRI with cognitive-behavioral paradigms to explore the effects of functional lateralization(strength and direction)and lateralization patterns on behavioral performance.The results found that 1)Only the lateralization of executive functions was associated with behavioral performance and was mainly manifested as differences in the direction of lateralization rather than in the strength of lateralization,and 2)the functional lateralization patterns only affected behavioral performance for both executive controls,where the co-lateralization patterns had a behavioral disadvantage relative to the typical lateralization patterns.For the disadvantage effect of the co-lateralized individuals,the crowding hypothesis suggests that it may result from cognitive interference arising from competing neural representations.To test this hypothesis,Study 3 examined the cognitive-behavioral performance of different lateralization patterns with respect to interference effects based on a novel verbal-dynamic Landmark dual task in conjunction with a single-task paradigm.The results showed that 1)consistent with Study 2,there was still a significant behavioral disadvantage in the co-lateralized group,mainly in the visuospatial attention task,and 2)the co-lateralized group did have a stronger interference effect compared to the typically biased group,providing direct behavioral evidence for a cognitive interference mechanism.Study 4 explored the brain white matter lateralization using high angular resolution diffusion imaging techniques.The results showed that 1)the functional lateralization of visuospatial attention is mainly related to the corpus callosum,which connects the two hemispheres.To be specific,the stronger the functional lateralization of visuospatial attention,the weaker the connectivity of hemispheres,which provides evidence for the hypothesis of the excitatory role of the corpus callosum.2)The brain lateralization of word generation task is significantly positively correlated to the lateralization of withinhemispheric white matter pathways — arcuate fasciculus and superior longitudinal fasciculus-III,which link the brain language regions.In summary,the brain lateralization of word generation,visuospatial attention and response inhibition is interdependent,and the effects of them and patterns between them on behavior performance are domain-selective,with individuals with atypical lateralization directions and patterns having the behavioral disadvantage in the nonlanguage domain.Regarding the underlying structural basis of hemispheric lateralization,there are distinct mechanisms of inter-and intra-hemispheric white matter fiber connections in word generation and visuospatial attentional task.This study helps to understand the interaction mechanisms and the structure-function relationships between different brain cognitive functions from the perspective of lateralization and provides an important reference framework for the preoperative localization of patients with different brain functional lateralization in neurosurgery.