Hemispheric Specialization of Executive Functions: A Review of Brain Asymmetries

Executive functions are the higher-order capacities through which goals are formed, maintained and flexibly pursued. Although their dependence on the prefrontal cortex is well established, the differential contributions of the two cerebral hemispheres have received comparatively little systematic attention. This thesis reviews the evidence for hemispheric specialization of executive functions, examining the three core components: inhibitory control, working memory and cognitive flexibility. Chapter 1 sets out the conceptual framework for studying lateralization as a graded, function-specific property of neural systems. Chapter 2 introduces the core components and the bilateral frontoparietal network that supports them. Chapter 3 reviews the neuroimaging evidence in healthy adults; Chapter 4 reviews the converging evidence from focal-lesion, split-brain and clinical studies. Three distinct patterns emerge. Inhibitory control divides into two subtypes: response inhibition is weighted toward the right inferior frontal cortex within a bilateral network, while interference control shows a bilateral pattern centered on dorsolateral prefrontal cortex and the dorsal anterior cingulate. Working memory shows material-specific lateralization in posterior cortex: verbal content engages a left-lateralized perisylvian network, visuospatial content engages a right-lateralized frontoparietal network, while the prefrontal control system remains bilateral. Cognitive flexibility recruits a bilateral frontoparietal network in which lesion data reveal a finer division of labor between the two cerebral hemispheres. The findings argue against any account of executive lateralization as whole-hemisphere dominance. Instead, executive specialization can be characterized as a system of domain-specific asymmetries embedded within a broadly bilateral architecture.