The purpose of this study is to investigate brain activity during current visual and auditory tasks for balance control. The participants will perform cognitive, gait, and balance measures before the data collection to exclude people with neurological disorders. The participants will wear VR headset which provides visual tasks. The participants will need to maintain balance while performing concurrent visual and auditory tasks. The brain activities, reaction time, and eye-tracking data will be collected during doing our experimental tasks.

Virtual reality (VR), defined as an interactive system including computers and media peripherals, creates an environment similar to a real-world and also provides audio and video feedback to users. Recently, the virtual reality technology is able to make a headset displaying 360 degrees VR environment and locate the headset in the space. This improvement of VR technology significantly reduces the cost of VR equipment and enhances the application of VR technology in the field of balance assessment and treatment.

Optic flow (OF) has been used to study the effect of visual input on balance control. Most of the studies displayed OF on a screen rather than using 360 degrees visual field environment. Therefore, the subjects could obtain reference inputs for balance adjustment. The new VR headset makes it possible to play OF in a 360-degree visual field in which the subject will not able to obtain any reference inputs rather than using somatosensory and/or vestibular systems. It is unclear how the effect of aging and attention relocation affects postural control with concurrent visual and auditory attention tasks. In this study, fNIRS will be used to detect the brain activity of healthy adults in the prefrontal and temporal-parietal junction as they complete concurrent cognitive and visual tasks displayed by a VR headset. This work will focus on age and test positions (sitting vs standing). As age can play a role in brain activation levels, the investigators will compare results among younger adults (25-35 years), older adults (65-85 years), and older adults with the risk of falls. All the subjects will undergo concurrent auditory reaction time tasks and visual tracking tasks. The investigators will compare the brain images from the test conditions between the age groups and investigate if brain activity differs during the performance of reaction time tasks and visual tacking tasks. The goal of this study is to examine the effect of concurrent visual and auditory tasks on brain activation and postural control.

Inclusion Criteria:

• must not have any vestibular, orthopedic or neurological disorders, knee or hip replacements, reports of dizziness, low visual acuity (corrective vision less than 20/40) or require the use of an assistive device for ambulation.
• Right-handed

Exclusion Criteria:

• Healthy group: have a low fall risk profile based on current available clinical balance and gait assessment tools, such as the MiniBEST and STEADI fall risk self-assessment tool and normal cognitive status using the Montreal Cognitive Assessment (MoCA > 26/30)
• Fall risk group: other medical issues rather than balance problems

Healthy younger adults: aged between 25-45 years old Healthy older adults: aged between 65-85 years old Older adults with risks of falls: aged between 65-85 years old