Modulating the internal model of verticality by virtual reality and body-weight support walking: A pilot study

Spatial neglect encompasses impaired verticality representation after right hemisphere stroke

Spatial neglect after right hemisphere stroke (RHS) was recently found to encompass lateropulsion, a deficit in body orientation with respect to gravity caused by altered brain processing of graviception. By analogy, we hypothesized that spatial neglect after RHS might encompass an altered representation of verticality. We also assumed a strong relation between body neglect and impaired postural vertical, both referring to the body. To tackle these issues, we performed contingency and correlation analyses between two domains of spatial neglect (body, extra-body) and two modalities of verticality perception (postural, visual) in 77 individuals (median age = 67) with a first-ever subacute RHS (1-3 months). All individuals with a transmodal (postural and visual) tilt in verticality perception (n = 26) had spatial neglect, but the reverse was not found. Correlation and multivariate analyses revealed that spatial neglect (and notably body neglect) was associated more with postural than visual vertical tilts. These findings indicate that after RHS, an impaired verticality representation results from a kind of graviceptive neglect, bearing first on somaesthetic graviception and second on vestibular graviception. They also suggest that the human brain uses not only a mosaic of 2D representations but also 3D maps involving a transmodal representation of verticality.

Does the Management of Visual and Audible Motion Information during an Immersive Virtual Reality Timed Up and Go Test Impact Locomotor Performance in the Elderly?

BACKGROUND/AIMS

Falling among the elderly is a major public health issue, especially with the advancing age of the baby boomers. The fall risk assessment tests for many lack a context that would bring them closer to everyday life. Thus, immersive virtual reality, which makes it possible to simulate everyday situations, could make it possible to strengthen the quality of the assessment of the risk of falls. However, it is necessary to understand how the use of a virtual reality device influences the motor control of elderly participants. If vestibular physiotherapists use VR to virtualize their tools, what impact would a visual simulation of movement have on motor control in a locomotor task, if this simulation were plausible?

METHODS

Sixty-two elders (70.8 ± 6.7 years old) completed a Timed Up and Go task under 3 conditions: real, virtual reality, and virtual reality with visual and sound movement information. The virtual reality task takes place in a train either stationary at a station or in uniform linear motion. The time and number of steps were recorded using video, and comparisons between conditions were made using Friedman's test.

RESULTS

The results show a significant increase in the time and number of steps in "virtual reality" condition compared to the "real" condition. They do not show significant differences between the 2 virtual conditions.

CONCLUSION

The use of a running virtual train to provide plausible movement is particularly distinguished from vestibular physiotherapy applications with first a fixed visual support partially obscuring the optical flow. This visual aid coupled with the attention dedicated to the task inhibits the effect of the moving environment on locomotion. However, the visual optical flow will potentially have an effect in people with fear of falling. Virtual reality shows great potential for the simulation of realistic environments for the assessment of the risk of falls and opens up avenues for the development of tests.

Contribution of Basal Ganglia to the Sense of Upright: A Double-Blind Within-Person Randomized Trial of Subthalamic Stimulation in Parkinson's Disease with Pisa Syndrome

BACKGROUND

Verticality perception is frequently altered in Parkinson's disease (PD) with Pisa syndrome (PS). Is it the cause or the consequence of the PS?

OBJECTIVE

We tested the hypothesis that both scenarios coexist.

METHODS

We performed a double-blind within-person randomized trial (NCT02704910) in 18 individuals (median age 63.5 years) with PD evolving for a median of 17.5 years and PS for 2.5 years and treated with bilateral stimulation of the subthalamus nuclei (STN-DBS) for 6.5 years. We analyzed whether head and trunk orientations were congruent with the visual (VV) and postural (PV) vertical, and whether switching on one or both sides of the STN-DBS could modulate trunk orientation via verticality representation.

RESULTS

The tilted verticality perception could explain the PS in 6/18 (33%) patients, overall in three right-handers (17%) who showed net and congruent leftward trunk and PV tilts. Two of the 18 (11%) had an outstanding clinical picture associating leftward: predominant parkinsonian symptoms, whole-body tilt (head -11°, trunk -8°) and transmodal tilt in verticality perception (PV -10°, VV -8.9°). Trunk orientation or VV were not modulated by STN-DBS, whereas PV tilts were attenuated by unilateral or bilateral stimulations if it was applied on the opposite STN.

CONCLUSION

In most cases of PS, verticality perception is altered by the body deformity. In some cases, PS seems secondary to a biased internal model of verticality, and DBS on the side of the most denervated STN attenuated PV tilts with a quasi-immediate effect. This is an interesting track for further clinical studies.

Influence of vestibular signals on bodily self-consciousness: Different sensory weighting strategies based on visual dependency

Previous studies showed that the vestibular system is crucial for multisensory integration, however, its contribution to bodily self-consciousness more specifically on full-body illusions is not well understood. Thus, the current study examined the role of visuo-vestibular conflict on a full-body illusion (FBI) experiment that was induced during a supine body position. In a mixed design experiment, 56 participants underwent through a full-body illusion protocol. During the experiment, half of the participants received synchronous visuo-tactile stimulation, and the other half received asynchronous visuo-tactile stimulation, while their physical body was lying in a supine position, but the virtual body was standing. Additionally, the contribution of individual sensory weighting strategies was investigated via the Rod and Frame task (RFT), which was applied both before (pre-FBI standing and pre-FBI supine) and after the full-body illusion (post-FBI supine) protocol. Subjective reports of the participants confirmed previous findings suggesting that there was a significant increase in ownership over a virtual body during synchronous visuo-tactile stimulation. Additionally, further categorization of participants based on their visual dependency (by RFT) showed that those participants who rely more on visual information (visual field dependents) perceived the full-body illusion more strongly than non-visual field dependents during the synchronous visuo-tactile stimulation condition. Further analysis provided not only a quantitative demonstration of full-body illusion but also revealed changes in perceived self-orientation based on their field dependency. Altogether, findings of the current study make further contributions to our understanding of the vestibular system and brought new insight for individual sensory weighting strategies during a full-body illusion.

Effect of postural training using a whole-body tilt apparatus in subacute stroke patients with lateropulsion: A single-blinded randomized controlled trial

BACKGROUND

Lateropulsion after stroke is defined as a postural bias toward the paretic side and push away from the non-paretic side. New rehabilitation techniques and programs should be designed to attenuate lateropulsion and improve functions of balance and gait.

OBJECTIVE

This study aimed to determine the effects of whole-body tilting postural training (WTPT) using a Spine Balance 3D on lateropulsion and postural control as compared with general postural training (GPT). Postural training was performed and involved a whole-body tilt apparatus that enables postural training in the tilted position, in multiple directions.

METHODS

This was a pragmatic, single-blind, randomized controlled trial conducted between June 2018 and May 2019. We randomly allocated 30 patients with subacute stroke and lateropulsion based on the Scale of Contraversive Pushing (SCP score>0) to experimental (n=15) and control (n=15) groups. The experimental group received WTPT with a whole-body tilt apparatus, and the control group GPT. WTPT was performed with the Spine Balance 3D and GPT with postural training commonly applied in the clinic. All participants received treatment for 30min/session, 2 times/day, 5 days/week for 3 weeks. The primary outcome measure was lateropulsion assessed with the Burke Lateropulsion Scale (BLS). Secondary outcome measures were postural control ability, activities of daily living, Postural Assessment Scale for Stroke (PASS) score, Berg Balance Scale (BBS) score, Korea-modified Barthel index (K-MBI), and Fugl-Meyer Motor Assessment-Lower Extremity (FMA-L) score.

RESULTS

For the primary outcome, after training, BLS scores were decreased more for the experimental than control group (Δ=-5.8 vs. Δ=-4.2, P=0.002). For secondary outcomes, scores were improved more for the experimental than control group: PASS (Δ=13.8 vs. Δ=8.5, P<0.001), BBS (Δ=20.1 vs. Δ=11.1, P=0.001), K-MBI (Δ=27.0 vs. Δ=20.1, P=0.005), and FMA-L (Δ=10.2 vs. Δ=6.3, P=0.002).

CONCLUSIONS

WTPT is a potentially effective therapeutic intervention for lateropulsion recovery in patients with subacute stroke. It may be useful for improving postural control and activities of daily living.