title: Symmetries in human brain language pathways correlate with verbal recall.
abstract: Lateralization of language to the left hemisphere is considered a key aspect of human brain organization. We used diffusion tensor MRI to perform in vivo virtual dissection of language pathways to assess the relationship between brain asymmetry and cognitive performance in the normal population. Our findings suggest interhemispheric differences in direct connections between Broca's and Wernicke's territories, with extreme leftward lateralization in more than half of the subjects and bilateral symmetrical distribution in only 17.5% of the subjects. Importantly, individuals with more symmetric patterns of connections are better overall at remembering words using semantic association. Moreover, preliminary analysis suggests females are more likely to have a symmetrical pattern of connections. These findings suggest that the degree of lateralization of perisylvian pathways is heterogeneous in the normal population and, paradoxically, bilateral representation, not extreme lateralization, might ultimately be advantageous for specific cognitive functions.
authors.affiliation: Section of Brain Maturation, Department of Psychological Medicine, and Centre for Neuroimaging Sciences, Institute of Psychiatry, King's College London, London, United Kingdom. m.catani@iop.kcl.ac.uk
authors.forename: Marco
authors.initials: M
authors.lastname: Catani
authors.forename: Matthew P G
authors.initials: MP
authors.lastname: Allin
authors.forename: Masud
authors.initials: M
authors.lastname: Husain
authors.forename: Luca
authors.initials: L
authors.lastname: Pugliese
authors.forename: Marsel M
authors.initials: MM
authors.lastname: Mesulam
authors.forename: Robin M
authors.initials: RM
authors.lastname: Murray
authors.forename: Derek K
authors.initials: DK
authors.lastname: Jones
mesh_terms: D000328:Adult; D001921:Brain / Q000502:physiology*; D001931:Brain Mapping; D005260:Female; D007839:Functional Laterality; D006801:Humans; D007802:Language; D008297:Male; D011939:Mental Recall; D012727:Sex Characteristics; D014705:Verbal Behavior