Alien Hand Syndrome?

Alien hand syndrome sounds like something from a B-grade horror movie, but it's a real condition. You could be completely at the mercy of your own, renegade hand.

You're napping on a breezy Sunday afternoon in the hammock of your backyard, enjoying the peace and quiet of your suburban utopia. Slowly, your left hand eases up, wraps around your neck and you awake to find your own hand locked in a kung-fu grip on your throat. You pry it loose with your other hand, finger by finger, until it relents and you're left there staring at a hand that suddenly doesn't feel like your own. While it sounds like something from a B-grade horror movie, it's actually a very odd and very real medical condition known as "alien hand syndrome" (AHS).

Research has been sparse over the years due to the scarcity of cases, but a study by a team of Swiss doctors in July 2007 has shed new light on AHS. The doctors conducted functioning magnetic resonance imaging (fMRI) tests on a victim of AHS to determine what sections of the brain showed activity during planned and unplanned movements. They found that planned movements originated in the frontal lobe before being sent to the motor strip, while the alien movements showed no activity in the frontal lobe -- the movements originated from the motor strip itself. Furthermore, the signal remained in the motor strip without sending a message back to the frontal lobe, leaving victims unaware of their own movements. While the motor strip has finally been successfully singled out as the center of activity, it's still not known what triggers the signals to begin with, leaving the condition as a mysterious medical curiosity

most commonly after a radical procedure that treats extreme cases of epilepsy. When the callosum is damaged, it leaves the different sections of the brain disconnected and unable to speak to each other

Think of the corpus callosum as the brain's e-mail server, a bundle of message sending nerves that connect and share information with the two hemispheres. Alien hand syndrome is a result of damage to these nerves. This damage most often occurs in brain aneurysms, stroke patients and those with infections of the brain, but can also manifest as a side effect of brain surgery, most commonly after a radical procedure that treats extreme cases of epilepsy. When the callosum is damaged, it leaves the different sections of the brain disconnected and unable to speak to each other -- its e-mail is permanently down. With AHS, one hand functions normally, carrying out purposeful tasks without signaling the other hand, resulting in a limb that can act on its own, sometimes in opposition to the functioning side.