Cortical Contributions to Reflexive Postural Control: An Investigation Using Functional Near-Infrared Spectroscopy

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.