Plasticity of body representations after surgical arm elongation in an achondroplasic patient.

A realistic body representation needs to be constantly updated. In case of physiological modifications, body representations integrate information coming from different sensory sources, including the sense of touch. Previous studies described transient modifications of these representations following illusory distortions. In this single case study, we documented the changes occurred in lower-level, primary somatosensory, and higher-level representations, in a case of upper arms elongation. We explored effects of arm lengthening on primary tactile perception (sensitivity and acuity), an implicit perceptual measure of body size (tactile distance judgement), body image (Daurat-Hmelijak test), and peri-personal space representation (audio-tactile interaction task). We show that patient's arm representation was changed after surgery. Specifically, we observed significant changes on tactile distance judgments, body image test and audio-tactile interaction task; also even though no changes were found on primary tactile perception a significant modification emerged in tactile acuity. These findings are in line with evidence of cortical reorganization after arm elongation. They also support the view that the body representation of achondroplasics are modified after body-size reconstruction, and became similar to that of healthy controls.