Perceptual Adaptation with Selective Reductions of Felt Sensation

Hypnotic anesthesia was used to reduce sensation in the adapting arm during prism displacement. Magnitude of adaptation to displacement was assessed by negative aftereffects (NA), proprioceptive shifts (PS), and visual shifts (VS). Hypnotic anesthesia for the entire arm nearly eliminated adaptation as measured both by NA and PS. This was not the case when only portions of the arm (receptor joints) were selectively anesthetized. The sum of NA when different parts of the arm were left unanesthetized at different times equaled such adaptation produced when all those arm locations were left unanesthetized simultaneously. This was also the case for PS. VS, which involved no arm movements, was not affected by hypnotic anesthesia. Support for Wilkinson's component additive model (NA = PS + VS) was found only when the adapting arm was not anesthetized.