The vegetative and minimally conscious states are examples of what are referred to as disorders of consciousness. Patients in these conditions are more or less oblivious to goings-on in their surroundings – they exhibit few, if any, signs of conscious awareness, and are usually unable to communicate in any way. It is, therefore, extremely difficult to establish what these patients are experiencing, and the consciousness disorders are among the least understood, and most commonly diagnosed, conditions in medicine.
Although technologies such as functional neuorimaging have enabled clinicians to gain some insight into these conditions, proper assessment and diagnosis of patients are still major challenges, and there are big ethical questions regarding how they should be treated. However, researchers from the University of Cambridge have made what could be a significant advance.
If someone told you that they wanted to have a perfectly good leg amputated, or that they have three arms, when they clearly do not, you would probably be inclined to think that they are mentally disturbed. Psychiatrists, too, considered such conditions to be psychological in origin. Voluntary amputation, for example, was regarded as a fetish, perhaps arising because an amputee’s stump resembles a phallus, whereas imaginary extra limbs were likely to be dismissed as the products of delusions or hallucinations.
However, these bizarre conditions – named body integrity identity disorder (BIID) and supernumerary phantom limb, respectively – are now widely believed to have a neurological basis. Two forthcoming studies confirm this, by providing strong evidence that both conditions occur as a result of abnormal activity in a part of the brain which is known to be involved in constructing a mental representation of the body, or body image.