Look at the right side of your body. It’s yours, right? Or maybe it’s your neighbor’s…


Somatoparaphrenia is caused by damage to the right parietal lobe. The similarity of this disorder to BIID, coupled with the childhood onset of these disorders, suggest both may be congenital disorders, that is, present from birth. The disorder is a delusional belief concerning the contralateral lesional side of the body, meaning that the side of the body opposite the side of brain damage is affected.


This disorder should not be confused with asomatognosia, which is unawareness, rather than delusional disbelief, of a limb, usually the left arm.


Patients with somatoparaphrenia deny ownership of either a limb on one side of their body, or an entire side of their body. A sufferer might be adamant that their right arm and leg are not theirs, not part of their many cases, the denial of ownership is of a paralyzed limb. Often, it is the left arm that is denied, as this disorder comes up often in right-brain-damaged patients. The denied limb may even be treated as an individual, given a name, treated as a child and taken care of. This shows how much the patients really dissociate themselves from ownership of the limb.


What do you think some of these sufferers ask for in terms of treatment? You guessed it: amputation. Again, the ethical issues that come up in BIID amputations apply to somatoparaphrenia as well.


One individual, suffering not only from somatoparaphrenia, but also schizophrenia, believed his right arm and foot did not belong to him. He said that his arm belonged to a woman he knew named Maria, and that his foot could not belong to him because it was a “big foot only suited for work.” This case is considered one of the few in which schizophrenia and somatoparaphrenia are documented in the same individual.


You may think, “Well, why don’t you try to ‘prove’ to the patient that their limb is theirs? Why, you can pinch their denied arm, or kick their denied foot. Or you can hold up a mirror to them and ask them to move their denied limb. And once they realize they can move that limb, voila! Problem solved.”


If you thought something along those lines, you were thinking like a researcher. Problem is, even if these things are done to the patient, they still deny ownership of the affected limb.


 However, there has been some success with a mirror experiment. This experiment was the first to describe that viewing a limb through a mirror alters limb disownership of a previously denied limb. What was done was a simple technique:

Take two groups of somatoparaphrenia patients. One group viewed their denied hand as it lay on a table. The second group also laid their denied hand on a table, but in front of them was a mirror which reflected their hand. The patient then viewed their affected limb in the mirror. There was no way for the mirror-group patient to look at their hand because a cardboard cutoff was placed around their neck to prevent them from being able to see below their neck. The results are startling: the first group, with no mirror, continued to deny their limb. But the mirror group accepted their limb as their own, so long as they viewed it through the mirror. If they stopped viewing their limb in the mirror and looked down at their hand on the table, they reverted back to denying their hand.


This mirror experiment is very interesting and is reminiscent in some ways of the rubber hand technique. This technique goes something like this:


Stick someone in a chair in front of a table. On the table is his left hand, hidden from his view by a screen. On the table is a lifelike rubber left hand and arm. The subject focuses their eyes and attention on the rubber hand and arm. A scientist stroke both the person’s hand and the rubber hand simultaneously, in the same area of the hand. Guess what happens?


The person feels a sense of ownership of the rubber hand. As one subject put it: “I found myself looking at the dummy hand thinking it was actually my own.”


The rubber hand illusion suggests that our self-awareness of our body can be manipulated and even altered through the senses. In effect, the brain uses the sensory modalities to construct and distinguish self from non-self. What do you think this mean in terms of somatoparaphrenia?


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