Friday, June 20, 2014

Rubber Hands and Mirrors

According to V.S. Ramachandran's text, The Tell-Tale Brain, (2011) a phantom limb is the result of the brain map still representing the limb. Despite the limb no longer physically existing, the map of the limb still exists in the brain. The channel of the brain designated for the limb no longer receives signals for that part of the body.  Visual treatments mentioned in Ramachandran's text (2011) includes an optical illusion with mirrors. The mirrors were able to communicate with skin-and-muscle feedback with the visual feedback from the mirrors which occurred in the parietal lobe. Ramachandran (2011) notes that after several times using the mirror boxes, the patient's phantom limb disappeared.

Rosenblum's (2010) See What I'm Saying describes another phenomenon of neuroplasticity induced by a pretend limb. The rubber hand illusion occurs when a person is asked to sit at a table with their arms shoulder-width apart from each other with their forearms facing down against the tabletop, their hands are relaxed and their fingertips are touching the table. A divider is placed at the right of the left arm, making it no longer visible to the person. A rubber hand is then positioned in its place to appear as if it belonged to the person. Cloth covers the right and left arms so only the right hand and rubber "left" hand is visible to the person. The experimenter uses two small paintbrushes to simultaneously stoke the index finger of the visible rubber hand and the unseen left hand. After two and a half minutes, the person feels as if the rubber hand has become a part of their body and they begin to respond as if this is true. For example, the rubber hand causes the person to experience pain when the rubber finger is bent backwards or when the rubber hand is stabbed with a syringe. Responses to this are often screaming, grimacing, etc., but even the person's autonomic nervous system reacts. The person sweats, the heart rate increases, and the brain reacts as if it were truly in danger. Areas associated with pain anticipation, anxiety, and motor reaction such as the premotor areas, anterior cingulate cortex, and the insula. If the stroking was down asynchronously the manipulation of feeling the rubber hand as their own would be eliminated.

The mirror illusion and rubber hand illusion both show how important visual information influences your brain and other senses, for example, touch.

Ramachandran, V. S. (2011). The tell-tale brain: a neuroscientist's quest for what makes us human. New York: W.W. Norton.

Rosenblum, L. D. (2010). See what I'm saying: the extraordinary powers of our five senses. New York, NY: W. W. Norton.


  1. I have an army buddy that has a missing finger that got crushed in an accident on base. He always complained about his "finger" hurting even though its not there and he doesn't know why. I showed him this and now he's looking up ways to use this mirror therapy for his finger, that is if there is a version for upper limbs. Thanks for posting this.

  2. Collin,
    I am glad you found my post useful and hopefully the mirror therapy can help your friend! I learned about the process when reading The Tell-Tale Brain by V.S. Ramachandran, if you or your friend would be interested in reading it. I believe it can be used for hands as well. The book I mentioned also discussed how when Ramachandran touched different sections of an amputee's face, he felt sensation in his phantom hand and said it alleviated some of the pain and discomfort or itching sensations in the hand. By stimulating different parts of their face, different parts of the phantom limb were "stimulated." This article discusses the face stimulating phantom limbs in monkeys.

    And here is some more information about the Phantom Touch.

    Hope perhaps some of this is helpful for your friend. :)

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