Potential therapeutic application of prism adaptation for patients with left hemisphere lesions: effects on associative word priming

Objectives: Prism adaptation (PA), a perceptual distortion technique forcing realignment between ocular- and arm- proprioceptive reference frames, has shown promise as a therapeutic intervention for a surprising range of functional disturbances related to right hemisphere lesions. The current study sought to explore the potential application of PA therapy in patients with left hemisphere lesions.   
Methods: Semantic priming (SP) in a lexical decision task, which has been shown to be reduced in left but not right hemisphere lesioned patients (Henik et al, 1993), was measured before and after adaptation to both right and left refracting prism (in separate sessions) in 12 patients with left hemisphere lesions. PA effectiveness was confirmed with open loop pointing tasks before, post and late following PA. 
Results: Whereas there was no change in SP after PA in a group of healthy controls, a significant increase in semantic priming, compared to sham PA, was observed after PA in the patient group. These preliminary data also suggest that the increase in SP might be greater after adaptation to right 
Conclusions: PA may modulate mental processes mediated by the left hemisphere, and could potentially have therapeutic application.