It’s a disorder that makes you fling your cereal away, undress yourself in public, steal merchandise, and even look dangerous to the rest of the world. For over five decades, Alien Hand Syndrome has been puzzling patients and neuroscientists alike.

Despite the somewhat sci-fi inspired nickname, Alien Hand Syndrome is a disorder of the brain that affects our movement. It is typically prevalent in individuals diagnosed with severe epileptic seizures. The seizures are so awful that the individual undergoes a procedure that entails having a neurosurgeon cut out the portion of the brain that the storm of an epileptic seizure roots from  [1]   . When that doesn’t help the patient, the neurosurgeon takes a more radical and risky approach by literally severing the brain in two along the corpus callosum. This is what’s called a “corpus callosotomy”  [2]  . Having a portion of your brain cut out is something we usually don’t hear of these days but for some individuals, it has become the only last resort that works. . .until now.

A corpus callosotomy is a big word and a big procedure that sounds extremely intense. First, let me explain how our hemispheres work together in order to help us interact with the world. The brain is basically two halves that form a whole. The two halves consist of the left hemisphere and the right hemisphere. Typically, the left hemisphere (responsible for language, speech, and motor functioning) controls the right side of the body whilst the right hemisphere (responsible for visual and spatial recognition) controls the left side of the body (see figure 1). The corpus callosum is the middle part of the brain that connects these two hemispheres and allows them to successfully communicate with one another through a band of neural fibers that bridges these two hemispheres together. When these two hemispheres cooperate with one another, we can function “normally” with the world. In a corpus callosotomy, this bridge and these neural fibers are severed, and the bridge is broken. The patient, as a result, becomes “split-brained”  [3]  . This is where things start to get interesting.

Figure 1. An example of how our hemispheres work separately in order to piece words and images together. Photo Courtesy of Ying Chen.

Split-brained patients have an issue with their brain hemispheres communicating with one another because the line of communication is cut. This makes it nearly impossible for individuals to function as normally as they would have before the procedure was performed. Issues that arise from the surgery result in a difficulty in recognizing words or images that lead to a lack of effective communication between brain hemispheres. For example, a study done by Michael Gazzaniga, a leading neurobiologist, psychologist, instructor, author, & researcher in split-brain patients for over 50 years, showed that individuals see and do two entirely separate things when a word is flashed on a screen on different sides of the brain. In his study, when the word “face” was flashed on the right side of the patient, the left hemisphere recognized the word and could say it out loud because it is the part of the brain responsible for speech and verbal recognition. When the same word, “face”, was flashed on the individual’s left side, the individual could say they saw absolutely “nothing” because the right brain (responsible for visual and spatial recognition) would not be able to recognize, nor say what it saw, but the individual would be able to draw a picture of a face  [4]  . The two hemispheres were not working together to allow the individual to say the word and draw it, regardless of what side it was on. See below (skip to 1:22 for actual footage from the study):

The video above really encompasses what Joe’s life is like and how his brain works. It’s amazing to think that our brains act as two separate entities, two separate consciences, when the part that bridges them together is removed. This video really puts into context how our brain hemispheres work together and Michael Gazzaniga has shown us awe-inspiring and completely eye-opening evidence proving the existence of split-brain. Now that we’ve seen how these affect our minds, let us examine how this affects our bodies.

Karen Byrne, a woman from New Jersey who has had epileptic seizures since she was 10 years old elected to do the surgery at 27 and has been affected by it ever since. Although her epilepsy had been cured after the corpus callosotomy, Miss Byrne had an inability to control her left hand. It was as if some sort of “alien” force was controlling her hand for her. Without thinking, Karen’s hand would begin undressing herself, or stubbing out her newly lit cigarette. Her hand would literally remove things out of her purse and she would have no idea. But even worse – her left hand would repeatedly slap her in the face, and she could not stop it  [5]  . Her right hand would try to correct the left, but her left hand would continue to do what it was doing and would not stop. It was as though she had no apparent free will because her left hand & her right hemisphere had a mind of its own. After 18 years of dealing with this largely life obstructing inconvenience, post surgery, doctors on the case discovered a new, unnamed medicine that put a stop to these battling, contradicting, and separate wills. Finally Karen was free of seizures and free to control her motor functioning. See the video here .

Although the study of Alien Hand Syndrome has been ongoing for decades now, it is still a disorder that we really do not know much about. As of right now, the only thing we know about it is the very fact that it is a miscommunication between the brain hemispheres and the body, and that it deeply affects individuals dealing with it. Hopefully in the future, neuroscientists and psychologists will collaborate and ultimately discover a way to permanently stop seizures in patients without the drastic surgeries and untested or overused medications. But for now, picture being in the shoes of a split-brained patient like Joe or Karen. How would that make you feel? What would you rather deal with – 18 years of seizures, or 18 years of not being able to control your own two hands?

  1. Schachter, S. (2014, March 1). What Happens During A Seizure? l Epilepsy Foundation. Retrieved November 12, 2014, from
  2. Corpus Callosotomy. (n.d.). Retrieved November 12, 2014, from
  3. Chudler, E. (2011, January 1). Neuroscience For Kids – Hemispheres. Retrieved November 12, 2014, from
  4. Wolman, D. (2012, March 14). The Split Brain: A Tale of Two Halves. Retrieved November 12, 2014, from
  5. Mosley, M. (2011, January 20). Alien Hand Syndrome sees woman attacked by her own hand. Retrieved November 18, 2014, from