Middle Temporal Gyrus

(Steps are referring to the right hemisphere MTG in the figures)

  1. For the MTG, it is necessary to have a 3D object model in order to reference the MTG upper and lower boundaries. The upper boundary of the MTG is the superior temporal sulcus and the lower boundary is the inferior temporal sulcus. In order to easily identify the inferior temporal sulcus, keep in mind that the inferior temporal sulcus is somewhat parallel to the superior temporal sulcus. Sometimes the inferior temporal sulcus gets interrupted by gyri but because the middle temporal gyrus has a consistent width, cutting across the interrupted portion of the inferior temporal sulcus to maintain a consistent MTG width is a good way to approximate where the inferior temporal sulcus would be in those areas. It is also helpful to note that the MTG in the right hemisphere is slightly more at an inclined slope due to the more inclined slope of the sylvian fissure in the right hemisphere. Therefore the MTG in both hemispheres is slightly asymmetrical. (Fig. 1, Fig. 2)
  2. On the 3D object model, click on the spot where the inferior temporal sulcus is the clearest, usually in the middle part of the MTG. Start in the corresponding slice in the coronal view. Trace the superior temporal sulcus to the end of the sylvian fissure. Trace the inferior temporal sulcus and also cut across to the end of the sylvian fissure. Working from this slice and moving to more anterior slices will help to identify the most accurate anterior end of the MTG. (Fig. 3, Fig. 4, Fig. 5)
  3. When the temporal stem disappears, trace the inferior temporal sulcus to its end point, cut to the superior temporal sulcus and trace the superior temporal sulcus. Continue to follow this step until then upper and lower boundaries of the MTG are no longer distinguishable. To identify the most anterior end of the MTG, it is necessary to reference the 3D object model to confirm where the upper and lower boundaries disappear. Keep in mind that the anterior end of the temporal lobe ends with the superior temporal gyrus, middle temporal gyrus and inferior temporal gyrus merging together similar to stripes on a watermelon (albeit not as perfectly—the superior temporal gyrus and MTG may appear before the inferior temporal gyrus). (Fig. 6, Fig. 7,Fig. 8, Fig. 9)
  4. To identify the posterior end of the MTG, return to the clearest point of the superior temporal sulcus. From the corresponding slice in the coronal view, work towards more posterior slides. Trace both the superior temporal sulcus and the inferior temporal suclus to the end of the sylvian fissure in order to have the two boundaries meet. (Fig. 10, Fig. 11)
  5. When the sylvian fissure disappears, trace the inferior temporal sulcus to its end point, cut to the superior temporal sulcus and trace the superior temporal sulcus. Continue this step until the superior temporal sulcus and the inferior temporal sulcus are no longer distinguishable. Again refer to the 3D object model to help identify the posterior boundary of the MTG. (Fig. 12, Fig. 13, Fig. 14)