Electronic Thesis and Dissertation Repository

Thesis Format

Monograph

Degree

Master of Science

Program

Neuroscience

Supervisor

Dr. Sue Peters

Abstract

Abstract: In 2017, falls ranked as the 18th leading global cause of age-standardized disability (Collaborators, 2018). Understanding the cortical mechanisms involved in balance control is essential for reducing fall risk. The supplementary motor area (SMA) has been implicated in balance control, but its role during postural reflex control is less understood. This study used functional near-infrared spectroscopy (fNIRS) to examine SMA activity in response to postural perturbations ranging from 0.25 to 1.9 m/s². Nine healthy young adults experienced uncued forward and backward perturbations every 41-49 seconds, eliciting both stepping and feet-in-place responses. The mean coefficient of variation remained below 5% in the regions of interest, confirming high signal quality. SMA activation increased as perturbation accelerations exceeded the stepping threshold. These findings implicate the SMA as a contributor to the use of a stepping response during postural reflex control.

Summary for Lay Audience

Falls are much more common in older adults over the age of 65 than in younger populations. When older adults fall, they’re also at a higher risk of serious injury or death, which can severely impact their quality of life. That’s why it’s so important to understand what causes these falls and particularly how the brain controls balance, so that one day we can develop better treatments and prevention strategies. This study focused on learning how the brain contributes to balance in healthy young adults, to form a baseline of how balance is controlled when everything is working well. By understanding this, we can better identify what changes might occur in aging or clinical populations that lead to more frequent falls. Specifically, we investigated a brain region called the supplementary motor area, which has been shown in past research to play a role in maintaining balance. Nine healthy participants stood on a moveable platform while wearing a functional near-infrared spectroscopy cap to record brain activity. The platform moved forwards and backwards unexpectedly and at different speeds to simulate varying levels of instability, participants were told to do their best to not take a step and to take a step only if they felt they were going to fall. We used a statistical method called a mixed-effects linear regression model to analyze how brain activity changed across different levels of instability, and whether or not a step was taken. We found that when the platform moved slowly and participants took a step, activity in the supplementary motor area increased more than when they kept their feet in place. However, when the platform moved quickly, supplementary motor area activity increased regardless of whether a step occurred or not. These results suggest that the supplementary motor area is actively involved in helping the body recover from balance loss, either by helping coordinate a stepping response or by supporting other ways of regaining stability. Ultimately, this research helps us better understand how the brain helps prevent falls and lays the foundation for future work aimed at reducing fall risk through rehabilitation or targeted therapies.

Creative Commons License

Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.

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