Could placebo or nocebo effects have an impact on implicit motor learning?

Gait-modifying effects of augmented-reality cueing in people with Parkinson’s disease

“…For example, step-length-modulating AR cues may assist in (i) increasing the typically short step lengths seen in people with PD (55) and (ii) alleviating FoG, considered to be one of the most disabling symptoms in people with PD, elevating fall risk and reducing quality of life (56). In doing so, one could ultimately take advantage of the flexibility (selecting the most effective type of cue) and personalization (tailoring the cues to individual's gait characteristics) potential of AR cueing, as cueing is not a one-sizefits-all principle (1,17). Additional benefits that AR-cueing applications may offer besides flexibility and personalization are (i) multimodality (e.g., visual cues, auditory cues, or both), (ii) cue activation [e.g., making use of headset-data features (20), on-demand activation with voice commands (23) or intelligent open-loop vs. closed-loop cueing (57)] and (iii) spatial awareness (e.g., merging visual cues to features in mapped environments).…”

“…Even though early AR cueing research in people with PD with the first-generation AR headsets did not find any significant improvements on FoG, the results were still encouraging as subjective benefits of AR cueing are often reported (23)(24)(25). The lack of positive findings may be related to the limited AR field of view (AR-FOV) of the AR headsets (18,23,26,27), an insufficient familiarization period to AR headsets (23), the fact that only one specific visual cue was implemented (1,17), or the emphasis on FoG as an outcome measure instead of other valuable gait characteristics like gait speed and step length, susceptible to improvement with AR cueing (20,25,28,29). In the present study we address these issues.…”

“…Also, the coupling strength between steps and cues varies with cueing modalities: the stronger gait is tied to the cue, the greater the gaitmodifying effects of the cues, yielding superior effects for visual cues (14,15), followed by auditory and somatosensory cues. As the response of people with PD to cueing is highly variable [e.g., a person with PD showing responsiveness to 3D cues, but not to 2D cues (16)], flexibility is required for tailoring cues to this heterogeneity, as well as to individual-specific gait characteristics (1,17), which may be challenging for some existing one-size-fits-all types or forms of cueing.…”