Also known as body schema disturbance, *somato-éidolie, *disorder of corporeal awareness, illusion of corporeal transformation, and illusion of corporeal displacement. All six terms are used to denote an illusory change in the size, relation, position, and/or movement of one's own body parts.Some examples of body schema illusions are *kinaesthetic hallucinations, *proprioceptive hallucinations, *microsomatognosia, *macrosomatognosia, *splitting of the body image, *aschematia, the *rubber hand illusion, the *illusory displacement of limbs, the *illusory arm extension, the *Pinocchio illusion, *Aristotle's illusion, and the *floating finger illusion. In clinical practice, the majority of the body schema illusions affect only a part (or various parts) of the body. Rare instances where the whole body is involved are referred to as whole body schema illusion. Pathophysiologically, body schema illusions are associated primarily with lesions affecting those parts of the parietal lobe or parieto-occipital region involved with bodily representations and/or representations of movement. Etiologically, they are associated primarily with paroxysmal neurological disorders such as migraine and epilepsy. It has been speculated that the topological distribution of symptoms in body schema illusions reflects the extension of the representation of body parts in the brain's sensory maps. As noted by the British neurologist Macdonald Critchley (1900-1997), these sensory maps would seem to extend far beyond the parietal lobe. As Critchley maintains, "Positive and negative modifications of corporeal awareness may be met with in lesions at all levels of the neuraxis, but the parietal lobes occupy a special and important role in this problem. More particularly, the parietal region ofthe minor hemisphere is commonly regarded as being of special significance, and there has been a tendency to speak of 'localization' or 'representation' of the body image within this particular region of the brain. This mode of thinking is probably a dangerous oversimplification." In 1963, Critchley proposed the term corporeal awareness as an alternative for the expressions body image and body schema, arguing that these latter terms "fail to indicate the combined properties of a concept and a percept". As a corollary, Critchley designates body schema illusions as 'disorders of corporeal awareness'.
References
Critchley, M. (1965). Disorders of corporeal awareness in parietal disease.In: The body percept. Edited by Wapner, S., Werner, H. New York, NY: Random House.
Leker, R.R., Karni, A., River, Y. (1996). Micro-somatoagnosia: Whole body schema illusion as part of an epileptic aura. Acta Neurologica Scandinavica, 94, 383-385.
Podoll, K., Robinson, D. (2000). Macrosomatognosia and microsomatognosia in migraine art. Acta Neurologica Scandinavica, 101, 413-416.