Neglect treatment by prism adaptation: what recovers and for how long.

Previous findings showed that a prism adaptation (PA) treatment can induce a long-lasting recovery of hemispatial neglect, at least up to five weeks after the end of the treatment programme (Frassinetti et al., 2002). The present study further evaluated the effects of PA by investigating: (1) the long-term duration of the benefits assessed one week, and one, three and six months after the treatment; (2) the generalisation of the effects to different visual and non-visual functions; and (3) the index of visuo-motor responses (adaptation effect or after-effect) that better predict neglect recovery by PA. To these aims, 21 neglect patients were submitted to PA treatment for 10 daily sessions over a period of two weeks, and their performance was assessed for visual, tactile, proprioceptive, motor and oculomotor functions. The results showed a consistent and stable amelioration of visuo-spatial abilities, both for personal and extrapersonal space. The improvement seems to be partially multimodal, since an amelioration was found for tactile modality, but not for proprioception and motor functions. Finally, neglect amelioration appeared to depend on patients' ability to adapt to prism optical displacement during the fist week of PA, since patients who were not able to correct pointing errors under prism exposure in the first week of treatment showed less neglect and oculomotor system recovery at the end of treatment.