Thesis defense Mitchel Stokkermans (Donders Series 620)

8 September 2023

Promotors: Prof. Dr. V.G.M. Weerdesteyn and Dr. M.S. Cohen
Co-promotor: Dr. T. Solis Escalante

Mind your step, Cortical dynamics during the human reactive balance response

This thesis investigates the role of the cortex in postural balance control and reactive balance responses. Although we often don't consciously notice it, maintaining upright posture requires cognitive processes. Patients with cortical lesions, such as stroke survivors, show balance impairments, suggesting cortical involvement in balance. The thesis explores cortical correlates of balance monitoring throughout different phases of the balance response.

Chapter 2 establishes that cortical responses to balance perturbations relate to the perturbation intensity and the need for a step response. This suggests cortical control may facilitate balance monitoring. Chapter 3 further investigates theta dynamics and finds that midfrontal theta dynamics play a role in action monitoring during forward reactive balance responses.

In Chapter 4, the focus shifts to foot strike events after stepping responses. Foot strikes trigger midfrontal theta power increase, and these theta dynamics may represent a step performance monitoring process rather than monitoring balance stability.

Chapter 5 examines cortical interactions with leg muscles during a reactive stepping task. The cortex interacts with leg muscles following perturbation onset, but lateralized muscle recruitment suggests subcortical regions may be more involved in the stepping response.

The thesis sheds light on the cortical mechanisms underlying postural control, offering insights into balance monitoring and reactive balance responses. It also presents potential future research directions and considerations for investigating balance impairments in clinical populations.