Morphology, morphometry and probability mapping of the pars opercularis ofthe inferior frontal gyrus: an in vivo MRI analysis

The pars opercularis occupies the posterior part of the inferior frontal gy rus. Electrical stimulation or damage of this region interferes with langua ge production. The present study investigated the morphology and morphometr y of the pars opercularis in 108 normal adult human cerebral hemispheres by means of magnetic resonance imaging. The brain images were transformed int o a standardized proportional steoreotaxic space (i.e. that of Talairach an d Tournoux) in order to minimize interindividual brain size variability. Th ere was considerable variability in the shape and location of the pars oper cularis across brains and between cerebral hemispheres. There was no signif icant difference or correlation between left and right hemisphere grey matt er volumes. There was also no significant difference between sex and side o f asymmetry of the pars opercularis. A probability map of the pars opercula ris was constructed by averaging its location and extent in each individual normalized brain into Talairach space to aid in localization of activity c hanges in functional neuroimaging studies.