Exploring the effects of ecological activities during exposure to optical prisms in healthy individuals

Abstract

Prism adaptation improves a wide range of manifestations of left spatial neglect in right-brain-damaged patients. The typical paradigm consists in repeated pointing movements to visual targets, while patients wear prism goggles that displace the visual scene rightwards. Recently, we demonstrated the efficacy of a novel adaptation procedure, involving a variety of every-day visuo-motor activities. This “ecological” procedure proved to be as effective as the repetitive pointing adaptation task in ameliorating symptoms of spatial neglect, and was better tolerated by patients. However, the absence of adaptation and aftereffects measures for the ecological treatment did not allow for a full comparison of the two procedures. This is important in the light of recent findings showing that the magnitude of prism-induced aftereffects may predict recovery from spatial neglect. Here, we investigated prism-induced adaptation and aftereffects after ecological and pointing adaptation procedures. Forty-eight neurologically healthy participants (young and aged groups) were exposed to rightward shifting prisms while they performed the ecological or the pointing procedures, in separate days. Before and after prism exposure, participants performed proprioceptive, visual, and visual-proprioceptive tasks to assess prism-induced aftereffects. Participants adapted to the prisms during both procedures. Importantly, the ecological procedure induced greater aftereffects in the proprioceptive task (for both the young and the aged groups) and in the visual-proprioceptive task (young group). A similar trend was found for the visual task in both groups. Finally, participants rated the ecological procedure as more pleasant, less monotonous, and more sustainable than the pointing procedure. These results qualify ecological visuo-motor activities as an effective prism-adaptation procedure, suitable for the rehabilitation of spatial neglect.

Different Effects of Numerical Magnitude on Visual and Proprioceptive Reference Frames

“…The paradigms used by Ronchi et al (2011) and Fortis et al (2013) were employed (see also Redding and Wallace, 1997). Participants sat at a table with their head aligned with the mid-sagittal plane of their body, and stabilized by a chin-rest attached to the table.…”

“…This study aimed at verifying whether numerical magnitude may affect the estimation of bodily reference frames. Healthy participants were asked to perform three tasks, which assess egocentric coordinates, the proprioceptive (P), the visuo-proprioceptive (VP), and the visual (V) straight ahead (Redding and Wallace, 1997; Rode et al, 2003; Redding et al, 2005; Fortis et al, 2013). All these tasks have been extensively used across different studies to assess, for instance, body schema distortions in unilateral spatial neglect, sensory-motor transformations (i.e., prismatic adaptation), or the effects of neck-muscles stimulation (Biguer et al, 1988; Taylor and McCloskey, 1991; Farnè et al, 1998; Bartolomeo and Chokron, 1999; Ferber and Karnath, 1999).…”

Restoring abnormal aftereffects of prismatic adaptation through neuromodulation

“…A standard PA protocol of our laboratory was used (Fortis et al, 2013). Both patient MM and control participants adapted to rightward displacing prisms, using for pointing the right hand, in which the patient showed no dysmetria (Weiner et al, 1983).…”

“…Participants adapted to an 11.4°rightward visual shift, induced by 20-dioptre, base-left prism glasses (BLP; Optique Peter, Lyon, France). Visuo-motor adaptation was achieved by the execution of 90 manual pointing movements towards a visual target (a red pen) presented at 2 different positions (þ 10°rightwards, and À 10°l eftwards, with respect to the participant's body midline), in a pseudorandom fixed order (see Fortis et al, 2013 for details). Participants received instructions to point with their right fingertip to the pen, with a fast and accurate movement, and then to return to the initial position (right finger on the sternum).…”

“…The present single-case study addresses this issue in a patient with a stroke lesion involving the left cerebellum, and the occipital cortex bilaterally. Based on the evidence described above, we explored firstly whether and how such a lesion may alter PA itself, and its AEs in the proprioceptive, visual, and visual-proprioceptive domains (Fortis et al, 2013). Secondly, by means of transcranial Direct Current Stimulation (tDCS) delivered during the PA procedure, we investigated whether the neuromodulation (Vallar and Bolognini, 2011) of the activity of the PPC and the cerebellum, could restore in this patient the defective AEs, and the efficacy of PA. To this aim, the anodal stimulation was used in order to up-regulate the activity of the parieto-cerebellar network recruited by PA.…”