- The term aschematia comes from the Greek words an (not) and schèma (form, scheme, or topographic map). It translates roughly as an 'inadequate mapping of space'. The term asché-matie was introduced in or shortly before 1905 by the French neurologist Pierre Bonnier (18611918) as an umbrella term for a group of symptoms characterized by an inadequate representation of the space occupied by some part of the body. As Bonnier wrote, "It is the affliction due to which certain parts of ourselves cease to fit in with the notion that we have of our body. When taking up too much space, there is hyper-schematia; too little, hyposchematia;oraplace that is not appropriate, paraschematia." Bonnier proposed the term aschematia as an alternative for the older terms malfunctioning of the somatopsyche and " coenesthesiopathy. All three terms have been used to denote an alteration of bodily object representations due to a lesion to the right parietal lobe. Due to their subjective nature, " hyperschematia, " hyposchematia, and " paraschematia cannot be observed directly in an affected individual. Therefore, diagnostic procedures tend to rely on the indirect evidence provided by the affected individual's drawings. In these drawings, the left side of a clock appears bloated, for example, and the petals on the left side of a daisy tend to be drawn larger, as well as greater in number than on the right side. Aschematia is considered a productive and subconscious manifestation of neglect. It may be accompanied by " negative autoscopy. Aschema-tia is usually classified as a variant of the "body schema illusions.ReferencesBonnier, P. (1905). L'aschématie. Revue Neurologique, 13, 605-609.Rode, G., Michel, C., Rossetti, Y., Boisson, D., Vallar, G. (2006). Left size distortion (hyperschematia) after right brain damage. Neurology, 67, 1801-1808.
Dictionary of Hallucinations. J.D. Blom. 2010.