Functional topography of the low postcentral area

Object. The goal of this study was to establish a reliable method for identification of face and tongue sensory function in the lower central area. Methods. All positron emission tomography (PET) clinical activation studies performed over a 3-year period at the Montreal Neurological Institute and Hospital were evaluated by coresistering the PET images with three-dimensional reconstructions of magnetic resonance images obtained in the same patients. In addition to stereotactic coordinates and measurements based on distance from the sylvian fissure, gyral and sulcal landmarks were analyzed to determine their reliability in localizing the sensory areas of the tongue and lower face. The convolutional anatomy of the central area is an important guide to the identification of function. The sensory area of the tongue is recognized as a triangular region at the base of the postcentral gyrus: the sensory area of the lower face resides in the narrowed portion of the postcentral gyrus, immediately above the tongue area. Conclusions. Cortical landmarks such as the substrata of tongue and face sensory impressions are more reliable guides than stereotactic coordinates or measurements for localizing function.