Hemi-neglect is a neurological disorder defined as an inability to attend one side of space, usually the left one, and it commonly follows a unilateral brain injury. The current main rehabilitation technique is Prism Adaptation, during which patients go through reaching movements while experiencing a lateral visual shift induced by optical prisms and adapt to it, benefiting from a deviation towards the neglected side of space when the prisms are taken off. Another promising technique for neglect rehabilitation is Optokinetic Stimulation. During this procedure, moving stimuli directed to the neglected side of a patient's visual field shifts the attentional focus of the patient towards that side. Virtual reality can incorporate simultaneously both Prism Adaptation and Optokinetic Stimulation within a single paradigm, potentially amplifying the effect of both these tools. We have created a novel VR-based protocol combining the two rehabilitation methods, which aims to solve the limitations of the traditional PA-technique by offering an engaging experience in a realistic environment. As a prerequisite for testing the effect of this treatment paradigm on neglect patients, in the current study we aimed to understand the motor and perceptual effects this training induces in healthy participants. To do so, we simulated a neglect-like condition in 30 healthy subjects, through the induction of a rightward aftereffect following a leftwards shifted VR-based Prism Adaptation and/or a rightwards-directed Optokinetic Stimulation. After the manipulation, all the subjects were required to perform different VR-based measures of lateralization of spatial attention and motor orientation both pre- and post- experiment. After the tests, all the subjects were asked to fill a questionnaire about their hand agency, ownership and location perception, in order to assess their experience with the VR manipulation.
The results showed that the Virtual-Reality Prism Adaptation was able to induce a significant visuomotor aftereffect, of an amplitude comparable to the one induced by traditional prisms, and could therefore be a potential rehabilitation device, that will add to the known benefits of prism adaptation the profitable peculiarities of virtual reality (gamification, ecological environment, remote guidance, etc.). Further experiments are needed to establish the presence and the amplitude of spatial attention aftereffect and to test the device on patients.