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SLIDE 4 Continued exposures along the sylvian fissure. The anterior horizontal ramus of the sylvian fissure separates the pars orbitalis and triangularis and the anterior ascending ramus separates the pars triangularis and opercularis. C, another right hemisphere. The lower end of the precentral gyrus is located behind a somewhat lobulated pars opercularis. The postcentral gyrus is located at the anterior edge of the supramar ginal gyrus, which wraps around the upturned posterior end of the sylvian fissure. D, the part of the right frontal and parietal lobes in front of and behind the pre- and postcentral gyri and central sulcus has been removed. The precentral gyrus is located lateral to the posterior part of the body of the ventricle. The postcentral gyrus is located lateral to the anterior part of the atrium. Both gyri adjoining the sylvian fissure are positioned lateral to the splenium of the corpus callosum. E-G, sulci and gyri of the frontal lobe. E, superolateral view of the left frontal lobe. The frontal lobe is often depicted as being split into three gyri, superior, middle, and inferior, by two sulci, superior and inferior. Often, as shown, the superior frontal gyrus is split into medial and lateral segments by irregular sulci and gyri. The middle frontal gyrus does not have a smooth, unbroken surface, but is broken up into multiple, tortuous segments. On the inferior frontal gyrus, formed by the pars orbitalis, triangularis, and opercularis, there can be multiple variations in the size and shape of the contributions from each part. The precentral gyrus, in this case, is broken up into several segments by limbs of the precentral sulcus. F, anterior view. A portion of the right superior frontal gyrus is broken into two longitudinal gyral strips. The left superior frontal gyrus is composed of multiple gyri that extend medially and laterally across the superior frontal area. The superior frontal sulci are continuous along both frontal lobes. The middle frontal gyri on both hemispheres are made up of numerous worm-like gyral segments. G, lateral view of another right frontal lobe. The pars triangularis and opercularis of the inferior frontal gyrus have a somewhat similar triangular appearance. Usually there is a gyral bridge at the lower margin of the central sulcus, but in this case the central sulcus opens into the sylvian fissure. The precentral gyrus is continuous from its lower to its upper margin and is not broken up into multiple segments as shown in B and E. The middle frontal gyrus is made up of multiple irregular convolutions. H-J, variations in the sulcal and gyral patterns of the temporal lobe. H, right temporal lobe with a more typical pattern in which the three temporal gyri, superior, middle and inferior, are separated by two sulci, superior and inferior. The sulci have an irregular, tortuous course, but are largely continuous along the lateral temporal lobe from anterior to posterior. I, the superior temporal gyrus located above the superior temporal sulcus is easily identifiable. The part of the temporal lobe below the superior temporal sulcus is broken up into multiple obliquely oriented gyri that do not fit easily into a pattern of the

expected middle and inferior gyri. J, the superior temporal gyrus is broken up into several segments but is fairly continuous. The middle and inferior temporal regions are formed by multiple obliquely oriented gyri and there is no clear inferior temporal sulcus