Cerebral Cortex Advance Access published online on October 21, 2009
Cerebral Cortex, doi:10.1093/cercor/bhp209
Effect of Familial Sinistrality on Planum Temporale Surface and Brain Tissue Asymmetries
1 Centre d'Imagerie-Neurosciences et Applications aux Pathologies UMR6232 CNRS, CEA, Université de Caen Basse-Normandie, Caen France, Université Paris Descartes Paris, France, 2 CHU de Caen, Neuroradiologie Caen France, 3 Institut Universitaire de France, Paris, France
Address correspondence to Nathalie Tzourio-Mazoyer, GIP Cyceron, Building. Becquerel, BP 5229, 14074 Caen Cedex, France. Email: tzourio{at}cyceron.fr
The impact of having left-handers (LHs) among one's close relatives, called familial sinistrality (FS), on neuroanatomical markers of left-hemisphere language specialization was studied in 274 normal adults, including 199 men and 75 women, among whom 77 men and 27 women were positive for FS. Measurements of the surface of a phonological cortical area, the "planum temporale" (PT), and gray and white matter hemispheric volumes and asymmetries were made using brain magnetic resonance images. The size of the left PT of subjects with left-handed close relatives (FS+) was reduced by 10%, decreasing with the number of left-handed relatives, and lowest when the subject's mother was left-handed. Such findings had no counterparts in the right hemisphere, and the subject's handedness and sex were found to have no significant effect or interaction with FS on the left PT size. The FS+ subjects also exhibited increased gray matter volume, reduced hemispheric gray matter leftward asymmetry, and, in LHs, reduced strength of hand preference. These results add to the increasing body of evidence suggesting multiple and somewhat independent mechanisms for the inheritance of hand and language lateralization.
Key Words: familial sinistrality • handedness • hemispheric specialization • language • planum temporale