Prism adaptation to a rightward optical deviation rehabilitates left hemispatial neglect

Abstract

A large proportion of right-hemisphere stroke patients show hemispatial neglect-a neurological deficit of perception, attention, representation, and/or performing actions within their left-sided space, inducing many functional debilitating effects on everyday life, and responsible for poor functional recovery and ability to benefit from treatment. The frequent parietal locus of the lesion producing neglect reflects the impairment of coordinate transformation used by the nervous system to represent extrapersonal space. Given that adaptation to a visual distortion can provide an efficient way to stimulate neural structures responsible for the transformation of sensorimotor coordinates, the aim of our study was to investigate the effect of prism adaptation on various neglect symptoms, including the pathological shift of the subjective midline to the right. All patients exposed to the optical shift of the visual field to the right were improved on their manual body-midline demonstration and on classical neuropsychological tests. Unlike other physiological manipulations used to improve neglect, this improvement lasted for at least two hours after prism removal and thus could be useful in rehabilitation programmes. The positive effect found for both sensorimotor and more cognitive spatial functions suggests that they share or depend on a common level of space representation linked to multisensory integration.

Orienting of attention in left unilateral neglect

“…In the terms of the proposal advanced by O'Regan and Noe È [169], it is thus not surprising that such an asymmetry in exogenous orienting may entail a dramatic lack of awareness for left-sided events when a concurrent right-sided event grabs patients' attention. Importantly, neglect patients may bene®t from maneuvers, such as active movements of their left limbs [172], or active adaptation to optical prisms that displace the visual scene rightward [173], which might be understood as temporarily restoring patients' mastery of sensorimotor contingencies associated with leftward orienting. We believe that these notions are promising and convincingly show that converging evidence from experimental psychology and neuropsychology may ultimately allow us to map in detail the ways in which attentional processes constitute`the mechanisms of consciousness' [174].…”

EFNS Guidelines on cognitive rehabilitation: report of an EFNS Task Force

“…The use of prism goggles deviating by 10°to the right, introduced relatively recently, was shown to improve significantly, in a transient fashion, neglect symptoms in one level Ib study (Rossetti et al, 1998). A recent level IIa study applied the prism goggle treatment for a 2-week period and obtained statistically significant improvement in the long term (Frassinetti et al, 2002).…”

Pain, body, and space: What do patients with complex regional pain syndrome really neglect?

“…The resulting errors in visually-guided reaching force to recalibrate visual and proprioceptive spatial coordinates towards the impaired hemispace and improve neglect symptoms (e.g. [32]). As compared to hemineglect consecutive to brain damage, a different strategy was proposed in CRPS: the prism intervention is aimed at shifting spatial frames away from the affected side [35,36].…”