Prism adaptation speeds reach initiation in the direction of the prism after-effect

Abstract

Damage to the temporal-parietal cortex in the right hemisphere often leads to spatial neglect-a disorder in which patients are unable to attend to sensory input from their contralesional (left) side. Neglect has been associated with both attentional and premotor deficits. That is, in addition to having difficulty with attending to the left side, patients are often slower to initiate leftward vs. rightward movements (i.e., directional hypokinesia). Previous research has indicated that a brief period of adaptation to rightward shifting prisms can reduce symptoms of neglect by adjusting the patient's movements leftward, toward the neglected field. Although prism adaptation has been shown to reduce spatial attention deficits in patients with neglect, very little work has examined the effects of prisms on premotor symptoms. In the current study, we examined this in healthy individuals using leftward shifting prisms to induce a rightward shift in the egocentric reference frame, similar to neglect patients prior to prism adaptation. Specifically, we examined the speed with which healthy participants initiated leftward and rightward reaches (without visual feedback) prior to and following adaptation to either 17° leftward (n = 16) or 17° rightward (n = 15) shifting prisms. Our results indicated that, following adaptation, participants were significantly faster to initiate reaches towards targets located in the direction opposite the prism shift. That is, participants were faster to initiate reaches to right targets following leftward prism adaptation and were faster to initiate reaches to left targets following rightward prism adaptation. Overall, these results are consistent with the idea that prism adaptation can influence the speed with which a reach can be initiated toward a target in the direction opposite the prism shift, possibly through altering activity in neural circuits involved in reach planning.

Visual Feedback Modulates Aftereffects and Electrophysiological Markers of Prism Adaptation

“…This early visual feedback could explain why the phasesensitive components measured in Experiments 1 and 2 had earlier latencies than what is typically reported for a P300 (Polich and Kok, 1995;Luck, 2005;MacLean et al, 2015). One approach to overcoming this limitation could be to occlude participants' vision until the moment they contact the screen using special goggles (e.g., PLATO goggles; see Striemer and Borza, 2017). It is unclear whether eliminating all visual input during the reach portion of each trial would impact PA's effects more broadly, but future studies could investigate this possibility.…”

Pushing attention to one side: Force field adaptation alters neural correlates of orienting and disengagement of spatial attention

“…Notably, there are also important differences in the pattern of ERP changes induced by prism (Martín‐Arévalo et al., ) and force field perturbations, including the apparent discrepancy in the symmetry of effects between leftward and rightward perturbations and target‐locked N1 effects. The idea that the motor plan to reach a location in space drives the allocation of spatial attention might help to explain the contrast between the bi‐directional effects on attention apparent after force field adaptation, and the fact that attention effects in healthy people are typically observed only after leftward prism adaptation (Goedert, Leblanc, Tsai, & Barrett, ; for review see Michel, ; but see Patané, Farnè, & Frassinetti, for bidirectional effects of prism adaptation; Striemer & Borza, ). Since prism adaptation requires only visuomotor goal remapping, and because the right parietal area can represent action goals in both hemifields, a leftward visual distortion may not require re‐allocation of neural resources to the left hemisphere in order to remap motor goals to right space.…”

Prism adaptation treatment for upper-limb Complex Regional Pain Syndrome: a double-blind randomized controlled trial

“…Conversely, participants with right-CRPS would use leftward-shifting prismatic goggles to induce adaptive realignment (movement after-effects) towards their affected side. Studies from neurologically healthy individuals and stroke patients show that these short-term movement after-effects are accompanied by a longer-lasting realignment of attention, spatial representations, and lateralised (ocular)motor performance in the same direction as the after-effect [3,13,21,40,44,[51][52][53]63,64,67,89,90,95,96,98,105].…”