| Introduction
Lateral Surface Gyri |
Once you have found these two major sulci, you should have no problem identifying other landmarks on the lateral surface of the cortex. You may have a little trouble finding the insular cortex and the primary auditory cortex. It's probably easier to find these regions in specimens that are not well fixed. To find the insular cortex, gently pull open the lateral fissure and look deep into the fissure. The "inusla" (island) is actually a quite recognizable feature on MRIs of the brain. The primary auditory cortex actually lies ont the surface of the superior temporal gyrus within the lateral fissure. A prominent feature is the transverse gyrus of Heschl, although you may not be able to see it without sectioning the brain. To find it, gently insert your finger into the lateral fissure and run it along the surface of the superior temporal gyrus. Within the posterior aspects of the fissure, you should find a "ridge" on top of the suprior temporal gyrus that extends back into the fissure from the lateral surface. This is the transverse gyrus which marks the auditory cortex. Mover your cursor over the picture to identify some of the landmarks you will find. Note that everything discussed in the lab manual is not necessarily labeled.
Two areas are highlighted in the image, one in the inferior frontal gyrus which includes the operculum (just anterior to the post-central gyrus) and part of the pars triangularis of the inferior frontal gyrus; and a second in the posterior aspects of the superior temporal gyrus, just below where you would be expected to find the primary auditory cortex. These two functional areas will usually be found in the left hemisphere of 90 - 95% of all individuals. What are these areas called and what is their functional significance? |
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