# A Virtual Reality Force Control Training System on Brain Activation: Functional Near-Infrared Spectroscopy (fNIRS) Study

## TL;DR

This study explores how adding force control to virtual reality hand-tracking systems affects brain activity in younger and older adults, aiming to improve hand function rehabilitation.

## Contribution

The novel VR input system integrates force control with hand tracking and demonstrates distinct brain activation patterns in different age groups.

## Key findings

- Adding force control increased oxygenated hemoglobin and decreased deoxygenated hemoglobin in key brain regions during gameplay.
- In older adults, the force control system activated the right PFC, bilateral M1, and right SMA more prominently.
- The novel system induced more widespread brain activity across all regions of interest compared to regular hand tracking.

## Abstract

Aging can bring upon several effects that can hinder one’s quality of life. One of the effects is the decline in one’s ability to perform activities of daily living, which is caused by the loss of hand function due to aging. To mitigate this, several virtual reality (VR)-based training or rehabilitation systems that use hand tracking were developed. Although these systems are effective, immersive, and can promote motivation, they are mostly limited to providing range of motion exercises. The addition of a force control component to the hand tracking of these systems could make them even more effective at improving or restoring hand function, as the majority of activities of daily living require a degree of force control.

This study aimed to compare the effects of 2 VR input systems: regular hand tracking and the novel VR input system in this study, which incorporate force control to regular hand tracking on the brain activity of younger and older adults. The degree of cortical activity during a training or rehabilitation task is linked to better functional outcomes and improvements of neuroplasticity.

Twelve younger adults (mean age 25.00, SD 4.50 years) and 12 older adults (mean age 73.00, SD 3.6 years) were recruited to play a game specifically developed for this study using 2 VR input systems. Brain activity during gameplay was recorded using functional near-infrared spectroscopy over the following cortical regions: prefrontal cortex (PFC), premotor cortex (PMC), supplementary motor area (SMA), and primary motor cortex (M1).

Compared with the regular hand-tracking system, adding a force control component increased average oxygenated hemoglobin (HbO) concentrations and decreased deoxygenated hemoglobin (HbR) concentrations in key brain regions. In young adults, these changes were observed in the right PMC and right M1. In older adults, higher HbO and lower HbR concentrations appeared in the right PFC, bilateral M1, and right SMA (HbR only). The force control component also led to more widespread activity across all ROIs.

The novel input system in this study can be used for improving or restoring hand function. The results of this study can be used as a reference for the development of better VR-based training or rehabilitation systems.