Software which is readily available to the neuroscience community can be used to reconstruct cortical surfaces from magnetic resonance imaging (MRI) data. Topologically correct cortical surfaces representing a white matter (WM) surface (which occurs at the white matter/gray matter interface) and a gray matter (GM) surface (which occurs at the gray matter/cerebrospinal fluid interface) can be created. Using these surfaces, we present an approach for producing a cortical mantle volume representing the gray matter. We then use this cortical mantle volume to restrict the analysis of functional MRI (fMRI) data to the gray matter. These results are then compared to a similar analysis using the entire masked volume.