Uncoupled leftward asymmetries for planum morphology and functional language processing.
Explanations for left hemisphere language laterality have often focused on hemispheric structural asymmetry of the planum temporale. We examined the association between an index of language laterality and brain morphology in 99 normal adults whose degree of laterality was established using a functional MRI single-word comprehension task. The index of language laterality was derived from the difference in volume of activation between the left and right hemispheres. Planum temporale and brain volume measures were made using structural MRI scans, blind to the functional data. Although both planum temporale asymmetry (t(1,99) = 6.86, p < .001) and language laterality (t(1,99) = 15.26, p < .001) were significantly left hemisphere biased, there was not a significant association between these variables (r(99) = .01,ns). Brain volume, a control variable for the planum temporale analyses, was related to language laterality in a multiple regression (beta = -.30, t = -2.25, p < .05). Individuals with small brains were more likely to demonstrate strong left hemisphere language laterality. These results suggest that language laterality is a multidimensional construct with complex neurological origins.
Eckert
Mark A
MA
Medical University of South Carolina, Department of Otolaryngology-Head and Neck Surgery, USA. meckert@stanford.edu
Leonard
Christiana M
CM
Possing
Edward T
ET
Binder
Jeffrey R
JR
D000293:Adolescent; D000328:Adult; D001921:Brain / Q000502:physiology*; D001931:Brain Mapping; D004292:Dominance, Cerebral / Q000502:physiology*; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D007802:Language; D008279:Magnetic Resonance Imaging; D008297:Male; D011795:Surveys and Questionnaires; D013702:Temporal Lobe / Q000502:physiology