LOCALIZATION OF THE MOTOR HAND AREA TO A KNOB ON THE PRECENTRAL GYRUS- A NEW LANDMARK

Using functional magnetic resonance imaging (fMRI) we have evaluated t he anatomical location of the motor hand area. The segment of the prec entral gyrus that most often contained motor hand function was a knob- like structure, that is shaped like an omega or epsilon in the axial p lane and like a hook in the sagittal plane. On the cortical surface of cadaver specimens this precentral knob corresponded precisely to the characteristic 'middle knee' of the central sulcus that has been descr ibed by various anatomists in the last century. We,ere then able to sh ow that this knob is a reliable landmark for identifying the precentra l gyrus directly. We therefore conclude that neural elements involved in motor hand function are located in a characteristic 'precentral kno b' which is a reliable landmark for identifying the precentral gyrus u nder normal and pathological conditions. It faces and forms the 'middl e knee' of the central sulcus, is located just at the cross point betw een the precentral sulcus and the central sulcus, and is therefore als o visible on the cortical surface.