Eye rotation does not contribute to shifts in subjective straight ahead: implications for prism adaptation and neglect.

Prism adaptation has received much attention in recent years as a potential method for the rehabilitation of visual neglect. Recent theories as to the underlying mechanisms include oculomotor resetting and pathological realignment of subjective straight ahead (SSA). Typical prism adaptation procedures involve both ocular rotation and manual correction making the precise mechanisms and contribution of these to the amelioration of neglect difficult to determine. This experiment separated the contributions of ocular rotation and manual error reduction to SSA realignment in normal participants by shifting the eye alone, the hand alone or both together. Rotating the eye alone did not contribute to SSA realignment whereas shifting the hand did.