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

Broca's area, which includes the pars triangularis (PTR), is a neuroanatomical region important in speech and language production. Linear measures of the PTR have been found to be asymmetric, with the direction of the asymmetry correlating with language dominance determined by Wada testing. It is unclear, however, whether these linear measurements correlate with volumetric measures, and it is also unknown whether white matter and/or gray matter contribute differentially to these asymmetries. To investigate these issues, volumetric magnetic resonance imaging methodologies were used to measure the PTR in a group of healthy right-handed men (n = 12). There was a significant leftward asymmetry of the PTR using linear and volumetric measures. Linear measures of the left and right hemispheres were highly correlated with volumetric measures. Underlying gray and white matter both contributed to PTR asymmetry. Anatomical boundaries and four configurations (V, U, Y, and J) are discussed with reference to potential interhemispheric differences.