Morphology of the frontal operculum: A volumetric magnetic resonance imaging study of the pars triangularis

Objective. Broca's area, which includes the pars triangularis (PTR), is a n euroanatomical region important in speech and language production. Linear m easures of the PTR have been found to be asymmetric, with the direction of the asymmetry correlating with language dominance determined by Wada testin g. It is unclear, however, whether these linear measurements correlate with volumetric measures, and it is also unknown whether white matter and/or gr ay matter contribute differentially to these asymmetries. To investigate th ese issues, volumetric magnetic resonance imaging methodologies were used t o measure the PTR in a group of healthy right-handed men (n = 12). There wa s a significant leftward asymmetry of the PTR using linear and volumetric m easures. Linear measures of the left and right hemispheres were highly corr elated with volumetric measures. Underlying gray and white matter both cont ributed to PTR asymmetry. Anatomical boundaries and four configurations (V, U, Y, and J) are discussed with reference to potential interhemispheric di fferences.