Phantom limbs, the self and the brain (the D. O. Hebb Memorial Lecture).

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Abstract
A phantom limb is universally experienced after a limb has been amputated or its sensory roots have been destroyed. A complete break of the spinal cord also often leads to a phantom body below the level of the break. Furthermore, phantom breasts, genitals and other body areas occur in a substantial number of people after surgical removal or denervation of the body part. The most astonishing feature of a phantom limb (or other body area) is its incredible "reality" to the person. An examination of phantom limb phenomena has led to four conclusions: the experience of a phantom limb has the quality of reality because it is produced by the same brain processes that underlie the experience of the body when it is intact; neural networks in the brain generate all the qualities of experience that are felt to originate in the body, so that inputs from the body may trigger or modulate the output of the networks, but are not essential for any of the qualities of experience; the experience of the body has a unitary, integrated quality which includes the quality of the "self".sbd.that the body is uniquely one''s own and not that of any other individual; the neural network that underlies the experience of the body-self is genetically determined but can be modified by sensory experience. A new theory has been developed to explain these conclusions. It is proposed that we are born with a widespread neural network.sbd.the "neuromatrix".sbd.for the body-self, which is subsequently modified by experience. The neuromatrix imparts a pattern.sbd.the "neurosignature".sbd.on all inputs from the body, so that experiences of one''s own body have a quality of self and are imbued with affective tone and cognitive meaning. The theory is presented with supporting evidence as well as implications for research.