Human cingulate and paracingulate sulci: pattern, variability, asymmetry, and probabilistic map.

Recent advances in functional neuroimaging of the human cerebral cortex revived interest in the study of the cortical morphology at both macro- and microscopic levels. By means of high-resolution magnetic resonance imaging (MRI), in vivo images of the human brain can be acquired and used to aid localization of the functional maps. The goal of the present study was to determine variability in the occurrence and location of the cingulate sulcus (CS) and the paracingulate sulcus (PCS). Brain MRIs of 247 healthy young volunteers were obtained and transformed into a standardized stereotaxic space (Talairach and Tournoux, 1988). The CS and PCS were marked in 494 hemispheres using software capable of real-time movement through a 3-D volume. The markers were used to generate a probabilistic map of the CS and PCS. The individual MRI images were also evaluated for the presence and location of the following morphological features: the continuity of the CS, the presence of vertically oriented branches of the CS, the presence of the PCS, and the presence of the intralimbic sulcus. The results revealed considerable variability in the location of some of the above morphological features and a striking hemispheric asymmetry in the prominence of the PCS. The results of four previous blood-flow activation studies of speech control were used to illustrate the relevance of our morphological findings for functional neuroimaging of the human anterior cingulate cortex.