If you like this talk, there's more Mary Roach on M&C: http://www.milkandcookies.com/link/106822/detail/

Mmmmmmm. Cheese crumbs.

That fetus is going TO HELL! Masturbation is a SIN!

amputees who have foot or knee orgasms, occur due to the plasticity of the brain. The somatasensory cortex, at the front of the Parietal lobe, is the center for feeling touch from the body. The order of body parts on this cortex is from mouth to anus (because you are a giant food-tube), starting at the top of your head and extending downward on either side to you ears, with the left side sensing the right side of your body and visa versa.

The plasticity of the brain with its ability to reorganize the functions of lobes in the cerebral cortex. So when an amputee loses his foot, the extra space for feeling his foot on the somatasensory cortex is consumed by the nearest organs on that cortext. Those being the ankle and the gentailia.

Further fun facts. Amputees who exprience missing foot orgasms have stronger orgasms because more of their somatasensory cortex is dedicated to their genitalia.

The Plasticity of the brain is so powerful that there is a documented case of a girl living a normal life while missing half of her cerebral cortex.