Prisms adaptation improves haptic object discrimination in hemispatial neglect.

Neglect manifestations are typically explored in the visual modality. Although they are less commonly investigated tactile deficits also exist, and the aim of this study was to explore neglect in this modality. A haptic object discrimination task was designed to assess whether or not shape perception is impaired in seven right brain damaged patients with or without neglect. Each patient's performance on the object discrimination task was assessed before and after a brief period of prism adaptation, a bottom-up rehabilitation technique known to improve neglect symptoms. The results suggest that a haptic deficit - in the form of substantially more left errors - is present only in patients with neglect. Following prism adaptation, the left bias error rates in neglect patients were substantially reduced, and were similar to those observed in patients without neglect. Moreover, the haptic processing of the right side of objects also improved slightly. This finding suggests an expansion of the effects of prism adaptation to the unexposed, tactile modality supporting the cross-modal central effect hypothesis.