Body schema and body image as internal representations of the body, and their disorders. An historical review.

Since the early 1900s, the terms body schema and body image denoted the internal representations of the body. Bonnier's (1905, Revue Neurologique, 13, 605) schema is a conscious spatial representation of the size, shape, and position of the body, and of body parts, whose dysfunction brings about aschématia, and hypo-, hyper-, and paraschématia. The two schemata of Head and Holmes (1911, Brain, 34, 102) are an unconscious plastic postural schema, for the maintenance of posture and balance and for the coding of the position of body parts, and a conscious superficial schema, for the localisation of somatosensory stimuli. Pick's (1922, Psychologische Forschung, 1, 303) body schema refers to a structural description of the body, including the position of body parts and their spatial relationships, defective in autotopagnosia. Schilder's (1935, The image and appearance of the human body) body image is a comprehensive construct, covering physiological, evolutional, neurological and neuropsychological, psychiatric and sociological aspects. Lhermitte's (1939, L'image de notre corps) image, based on the views of the abovementioned authors, is defective in bodily neuropsychological disorders. The two terms have been used interchangeably, to denote (hemi-)asomatognosia, anosognosia, autotopagnosia, depersonalisation, personal neglect, phantom and supernumerary limbs, somatoparaphrenia. Their properties have been summarized with general dichotomies: schema for action in space ("where" system), image for perception ("what" system), after primary sensory processing. While schema and image fractionated into multiple representations of aspects of the body, the two terms are still used to refer to some of these representations, and to their disorders.