Selective inability to point to extrapersonal targets after left posterior parietal lesions: An 0bjectivization disorder?

Abstract

A study of nine cases, selected from a systematic search for pointing disorders not explained by any known brain dysfunction, led to the description of incapacity of pointing to extrapersonal elements (allotopagnosia), particularly to other's body parts (heterotopagnosia), which was associated with lesions in the left posterior parietal region. Heterotopagnosia was present in the eight patients, in the absence of autotopagnosia in seven, and of any difficulty in pointing to body parts in a human representation (photograph or doll) in four, suggesting that it did not result from a disorder of the body representation. Heterotopagnosia was consistently associated with self-referencing behaviour, and with the confusion between self and others that it entails. From these clinical data it is suggested that the explanation of allotopagnosia lies, not in the affected category of objects, but in the pointing disorder Itself, which could be evidence of the impairment of a specifically human function of the left posterior parietal region responsible for objectivization.