CCN meeting | Guy Vingerhoets (Ghent University, Belgium), invited by Gilles Pourtois

Individual differences in brain organization: The text-book brain revisited

The human brain has an asymmetric functional organization with some functions preferring left hemisphere dominance while others prefer right hemisphere control. Lesion and neuroimaging research show that this division of labor between both sides of the brain has a strong population bias, meaning that most humans have their brain organized in the same way. Much less is known about individual differences in brain organization and how variations of the default phenotype affect cognition and behavior. We report the findings of an fMRI study that assessed hemispheric dominance of four lateralized cognitive functions (language and praxis for typical leftward dominance; spatial attention and face recognition for typical rightward dominance) in each of 200 participants which were also tested behaviorally. Results show atypical hemispheric functional segregation (HFS) in almost 30% of righthanders and in 50% of lefthanders. We will discuss the theoretical implications of the observed phenotypes for putative mechanisms of lateralization. Next, we investigate the relation between brain organization and cognition by analyzing the behavioral results of the current study of healthy participants and of participants with developmental dyslexia. We show that cognitive implications of atypical lateralization may be conditional on the inconsistency of a functional network’s lateralization resulting in a less efficient network. We conclude by discussing the clinical and theoretical implications of our findings.