The Untapped Potential of Virtual Reality in Rehabilitation of Balance and Gait in Neurological Disorders

Abstract

Dynamic systems theory transformed our understanding of motor control by recognizing the continual interaction between the organism and the environment. Movement could no longer be visualized simply as a response to a pattern of stimuli or as a demonstration of prior intent; movement is context dependent and is continuously reshaped by the ongoing dynamics of the world around us. Virtual reality is one methodological variable that allows us to control and manipulate that environmental context. A large body of literature exists to support the impact of visual flow, visual conditions, and visual perception on the planning and execution of movement. In rehabilitative practice, however, this technology has been employed mostly as a tool for motivation and enjoyment of physical exercise. The opportunity to modulate motor behavior through the parameters of the virtual world is often ignored in practice. In this article we present the results of experiments from our laboratories and from others demonstrating that presenting particular characteristics of the virtual world through different sensory modalities will modify balance and locomotor behavior. We will discuss how movement in the virtual world opens a window into the motor planning processes and informs us about the relative weighting of visual and somatosensory signals. Finally, we discuss how these findings should influence future treatment design.

Keywords: avatar; intervention; locomotion; posture; sensorimotor.

FIGURE 1 |

(A) Trunk excursion (top trace) to sinusoidal a-p translation (bottom trace) of the base of support (BOS) at 0.25 Hz. (B) Trunk excursion (top trace) to sinusoidal a-p optic flow (scene) at 0.1 Hz. (C) Trunk excursion (middle trace) when 0.25 Hz motion of the BOS (bottom trace) and 0.1 Hz of the scene (top trace) occur simultaneously. (D) FFT analysis demonstrating power at the trunk reflects frequency of the stimulus, i.e., the scene (left), the BOS (middle), and simultaneous BOS and scene motion (right).

FIGURE 2 |

Center of mass (COM) excursions during a-p translations of a platform at 0.25 Hz while standing in the dark (bold black line) and while viewing continuous pitch rotations of optic flow at 30 deg/sec (thin black line) and 45 deg/sec (bold gray line). Top graphs: responses to pitch-up rotations of the scene in a healthy 62-year-old adult (left) and 65 year-old-adult with right hemiplegia (right). Bottom graphs: responses to pitch down rotations of the scene in a healthy elderly adult (left) and elderly adult with stroke (right). Vertical thin line indicates start of optic flow field.

FIGURE 3 |

Step length ratio values exhibited by stroke survivors walking on a self-paced treadmill while exposed to avatar-based feedback in the visual, auditory, and combined (visual + auditory) sensory modality. Values are presented for the preadaptation (no avatar for 30 s), adaptation (avatar present for 1 min), and postadaptation periods (avatar removed for 1 min). Responders, that is individuals showing a reduction of their step length ratio during the adaptation period, are represented by a plain line, while non-responders are represented by a dotted line. Note the larger number of responders to the combined vs. individual sensory modalities.