Phantom limbs and the body schema.

AMPUTATED LIMBS persist as "phantoms" in their owners' consciousness. Temporary or permanent severance of afferent pathways may also give rise to subjective experiences in which the position of the phantom limb is different from that of the real one. Attempts have been made to explain phantom phenomena as expressions of a "body image" or "body schema" subserving a preconscious neurophysiological function. Varying interpretations have been placed upon the nature and behaviour of the theoretical body schema, but the original proposition of Head and Holmes remains the most satisfying. They proposed that the body image is formed and constantly changed by individual experience, and its role is a postural model, "against which all subsequent changes of posture are measured before they enter consciousness." No organized body of data exists to support the postural notion of the body schema, nor to define the limits of intrinsic plasticity proposed by Head and Holmes.