Testing cognition and rehabilitation in unilateral neglect with wedge prism adaptation: Multiple interplays between sensorimotor adaptation and spatial cognition

Abstract

Spatial neglect is a neurological condition characterised by deficits for perceiving, attending, representing, and/or performing actions within their left- sided space, responsible for numerous debilitating effects in everyday life, for poor functional recovery, and for decreased ability to benefit from treatment. Exposure to a right lateral displacement of the visual field (induced by a simple target-pointing task with base-left wedge prisms) is known to directionally bias visuomotor coordination and can be compensated by both sensorimotor adaptation and cognitive processes. Sensorimotor adaptation gives rise to after-effects whose duration is amplified in neglect patients and has been repeatedly shown to improve most neglect symptoms. Interestingly the effectiveness of PA has also been demonstrated for non-motor and non-visual tasks, such as for somatosensory extinction, for deficits in mental imagery of geographic maps and in number bisection, and even for visuo- constructive disorders, i.e. for unexposed sensory and motor modalities. Visuomotor adaptation appears to interact with higher-order brain functions related to multisensory integration and can have beneficial effects on sensory processing in different modalities as well as cognition. The bottom-up effects of prism adaptation on spatial cognition can also be applied to patients with complex regional pain syndrome who exhibit a spatial cognition bias towards the affected side. Such bottom-up effects exemplify the powerful potential of new approaches to rehabilitation that rely on physiological grounds and bypass intentional control, resulting in reduced attentional cost. We speculate that bottom-up effects may be completed by rounds of reverberation forming a virtuous circle leading to full-blown therapeutic effects.