Relations between biased tonicity of the body and vertical judgement in poststroke hemiplegic persons.

The influence of muscular tension upon visual vertical judgement in a standing posture was investigated in 16 hemiplegic persons and 12 normal elderly persons. The normal elderly group showed that their judgements of verticality were accurate and stable. In hemiplegic persons, judgements were displaced opposite to the side in which there was high tension in the body. Differences between groups in body tension and the side to which judgement was displaced were significant. The peculiar judgement errors made by hemiplegic persons are thus an overcorrection for tonicity. It was related to one's own body perception.