Indirect versus direct feedback in computer-based Prism Adaptation Therapy.

Prism Adaptation Therapy (PAT) is an intervention method in the treatment of the attention disorder neglect (Frassinetti, Angeli, Meneghello, Avanzi, & Ladavas, 2002; Rossetti et al., 1998). The aim of this study was to investigate whether one session of PAT using a computer-attached touchscreen would produce similar after-effects to the conventional box normally used in PAT. In four experiments, 81 healthy subjects and 7 brain-injured patients diagnosed with neglect were subjected to a single session of PAT under two conditions: (1) using the original box, and (2) using a computer-based implementation of PAT. The session of PAT included a pre-exposure step involving pointing at 30 targets without feedback; an exposure step involving pointing at 90 targets with prism goggles and feedback; and a post-exposure step involving pointing at 60 targets, with no goggles and no feedback. The results indicate that the expected similarity in the after-effect produced by the two conditions seems to occur only if subjects receive feedback on pointing precision by seeing their fingertip during the exposure step. Attempts to provide feedback indirectly via icons on the computer screen failed to produce the expected size in the after-effect. The findings have direct implications for computer-based treatment of visuospatial disorders in the future and computer-assisted rehabilitation in general.