Prism adaptation training (PAT) as a treatment for visuospatial neglect (VSN) involves two components: recalibration and realignment. We conducted a randomized controlled trial with PAT protocols requiring different degrees of recalibration and realignment, by using a single or multi-step protocol and varying visibility of the pointing movement. Twenty-five VSN patients received an alertness treatment without prisms, followed by four PAT protocols, encompassing a multi- or single-step procedure with terminal exposure, a single-step procedure with concurrent exposure, and sham PAT, presented in random order. The primary outcome parameter was the mean response time (RT) to left-sided targets in an endogenous variant of the Posner task, and we also measured the sensorimotor aftereffect. The two protocols without visibility of most of the movement trajectory produced significant aftereffects. The single-step protocol without movement visibility resulted in shorter RTs to left-sided targets. Hence, aftereffects depended on the partial invisibility of the movement. Moreover, only allowing VSN patients to recalibrate several times and direct feedback from the pointing errors had a beneficial effect on non-motor leftward visuospatial attention. We provide preliminary evidence that maximizing the conscious experience of movement errors may be an important component for remediating VSN.Trial registration: German Clinical Trials Register identifier: DRKS00025938.
Keywords: Prism adaptation training; Realignment; Recalibration; Terminal exposure; Visuospatial neglect.