Vestibular Rehabilitation Utilizing Virtual Environments to Train Sensory Integration for Postural Control in a Functional Context

System: The testing platform runs at 120 frames per second with either HTC Vive or Oculus Rift, on a Windows 10 laptop with 8GB RAM, Intel i7-7820HK CPU, Nvidia GTX 1080 Max-Q GPU, and Bose SoundTrue around-ear headphones II. The software was developed in C# with Unity3D 2018.2.0f1(64-bit) (Unity Technologies, San Francisco, California). The system utilizes SteamVR. Oculus Rift and HTC Vive both operate at 90 Hz refresh rate, 110 degrees field of view, and a high-definition video of 1080x1200 resolution for each eye. The graphics of the subway station, airport terminal building, and subway trains are modeled in Maya and imported to Unity3D. The rest of the 3D objects are modeled in Unity3D. The subway station model and airport model replicate a real subway station in New York City and a real airport terminal in the US. The contents in the system are fully controllable by the user interface (see Figure 3). Three-dimensional sounds were implemented using Wwise middleware and Google Resonance audio plugin. Using the head-tracking data, audio is modulated according to the position of the listener's head. The technology allows for creation of a rich soundscape in all directions around the listener. Audio assets used in the system are divided into two main groups: sound objects and ambiances. Sound objects are attached to the visual objects in the scene and their position is changing accordingly. Sounds include: footsteps, trains, announcements, cars, balls, airplanes, etc. Ambiances are created from original recordings from different locations in New York. These include different background sounds, i.e. sounds of the crowd chatter, distant trains, wind, birds, traffic, and general room tone of each of the spaces. All of the sounds used in the system are assigned to three different intensity levels which relate to the increasing complexity of the soundscape.

Data Collection: The first assessment session will include a well-established postural control assessment that the investigators had translated to a HMD paradigm and added an auditory layer. The protocol will include all possible combinations of the following: 2 levels of visual perturbation (static stars; stars moving in the AP direction, 0.2 Hz, 0.032m); 2 levels of auditory perturbation (quiet room; white noise that cycles from 0 to 1 dB at 0.3Hz), and 2 levels of support surface (floor; memory foam). Each scene will be 60 seconds long, there are 8 combinations, and each will be repeated 3 times for a total of 24 trials. Power spectral density (PSD) of sway in 3 frequency segments will be derived from a laboratory force plate and will serve to explore sensory integration mechanism. Participants will also complete the FGA (primary), VVAS (primary), ABC (descriptive), and DHI (descriptive).

Participants will complete the baseline assessment twice, one week apart, to assure stability of the measures. Following the baseline assessments, participants will be randomized to a C.S.I. experimental group (EG, n = 14) or a standard rehabilitation control group (CG, n = 14). The participants will commence the intervention program within a week of the second assessment. The setting will be a vestibular rehabilitation clinic at the New York Eye and Ear Infirmary of Mount Sinai.

Both groups: Eligible participants will be provided with patient education and a basic home exercise program (gait, balance, no exercises with eyes closed) while they are considering participation in the study.

Program Dose: 8 weeks, 1 visit per week, 30 minutes long EG: Progressive immersive training with the C.S.I. app; Scenes: start from most salient to the patient, eventually do all Duration: start at 60 seconds, increase over time up to 3 minutes per scene Complexity: start minimal, gradually increase up to most complex Tasks: standing with diverse base of support (BOS), head turns (progress with speed, planes); stepping, turning CG: Progressive gait, gaze stability and balance exercises. Gait: walking with head turns, progress with range, speed and planes of head movement; change of walking BOS: wide, normal, tandem Gaze: focus on a target while moving head side to side / up down. Progress with speed, duration, busier background, standing to walking.