Brain sarcasm areas found

Why is it, that when this story hit:

The researchers found that participants with prefrontal-lobe damage were significantly less able to understand sarcasm than those in the two other groups. Within the prefrontal group, people with damage in the right ventro-medial area, on top of the orbits of the eyes, had the most problems comprehending sarcasm. Those with the greatest damage to this area had the most difficulty.

more than one person commented that an easier way to find sarcasm centers in the brain was to do an MRI of my head and see which regions were bigger than normal? Let's just say my right ventro-medial prefrontal cortex is more than intact.