title: Strong rightward lateralization of the dorsal attentional network in left-handers with right sighting-eye: an evolutionary advantage.
abstract: Hemispheric lateralization for spatial attention and its relationships with manual preference strength and eye preference were studied in a sample of 293 healthy individuals balanced for manual preference. Functional magnetic resonance imaging was used to map this large sample while performing visually guided saccadic eye movements. This activated a bilateral distributed cortico-subcortical network in which dorsal and ventral attentional/saccadic pathways elicited rightward asymmetrical activation depending on manual preference strength and sighting eye. While the ventral pathway showed a strong rightward asymmetry irrespective of both manual preference strength and eye preference, the dorsal frontoparietal network showed a robust rightward asymmetry in strongly left-handers, even more pronounced in left-handed subjects with a right sighting-eye. Our findings brings support to the hypothesis that the origin of the rightward hemispheric dominance for spatial attention may have a manipulo-spatial origin neither perceptual nor motor per se but rather reflecting a mechanism by which a spatial context is mapped onto the perceptual and motor activities, including the exploration of the spatial environment with eyes and hands. Within this context, strongly left-handers with a right sighting-eye may benefit from the advantage of having the same right hemispheric control of their dominant hand and visuospatial attention processing. We suggest that this phenomenon explains why left-handed right sighting-eye athletes can outperform their competitors in sporting duels and that the prehistoric and historical constancy of the left-handers ratio over the general population may relate in part on the hemispheric specialization of spatial attention.
authors.affiliation: Université Bordeaux, GIN, UMR5296, Bordeaux, France; CNRS, GIN, UMR5296, Bordeaux, France; CEA, GIN, UMR5296, Bordeaux, France.
authors.forename: Laurent
authors.initials: L
authors.lastname: Petit
authors.forename: Laure
authors.initials: L
authors.lastname: Zago
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Mellet
authors.forename: Gaël
authors.initials: G
authors.lastname: Jobard
authors.forename: Fabrice
authors.initials: F
authors.lastname: Crivello
authors.forename: Marc
authors.initials: M
authors.lastname: Joliot
authors.forename: Bernard
authors.initials: B
authors.lastname: Mazoyer
authors.forename: Nathalie
authors.initials: N
authors.lastname: Tzourio-Mazoyer
mesh_terms: D000293:Adolescent; D000328:Adult; D001288:Attention / Q000502:physiology*; D001921:Brain / Q000502:physiology*; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009434:Neural Pathways / Q000502:physiology; D012438:Saccades / Q000502:physiology*; D013028:Space Perception / Q000502:physiology*; D055815:Young Adult
keywords: eye movements; eyedness; fMRI; handedness; hemispheric dominance; humans; right hemisphere; spatial attention