Within the disgusting recesses of your brain all of you have a cingulate sulcus: a deep groove that runs front-to-back along the medial sides of your hemispheres, just above he corpus callosum. You are neither interesting nor special if you have a cingulate sulcus - you are average.
However, there is a subset of individuals who have another groove running above and parallel to their cingulate sulcus. This additional groove is called the paracingulate sulcus, and it confers great honor upon its possessor. Before, all of you had a mere cingulate sulcus - but behold, I teach you the oversulcus; and those who overcome themselves are the bridge to the oversulcus.
As shown in the following video, the paracingulate sulcus is often readily visible, although I recommend using the sagittal and coronal slices to zero in on it; and to look about 15-20 millimeters anterior of the anterior commissure, and about 4-8 millimeters to the left and right of the longitudinal fissure. In particular, within the coronal section look for double invaginations stacked like pancakes. These folds correspond to the cingulate sulcus (ventral) and the paracingulate sulcus (dorsal). Furthermore, be aware that there are four possible combinations that you can see: Either there is no paracingulate sulcus; there is only one paracingulate sulcus, and it is either on the left hemisphere, or on the right hemisphere; or there are two paracingulate sulci, one on each hemisphere.
Regardless of whether a paracingulate sulcus makes you special or not, you may be wondering what the hullabaloo is all about; everyone's brain has some variability, you may say, and these differences wash out at a higher-level analysis. That may be true; but several experiments have also shown that the presence of a paracingulate suclus can significantly alter your results, as well as make the location of your results more uncertain (cf. Amiez et al, 2013). To remove these sources of variability, you can classify your subjects according to whether they are paracingulate-positive or not, and extract your beta weights from different regions of the medial prefrontal cortex.
I am doing an analysis like this right now, so feel free to follow me as I puzzle out how to apply this to my own dataset. I promise that the results will be, if not shockingly scandalous, at least spicy enough for your curiosity's appetite.