Master of Science
Health and Rehabilitation Sciences
Balance impairments are common after stroke. Reasons for this are multifactorial and include motor dysfunction and fatigue. Limited research has explored the combined effects of post-stroke fatigue and balance on brain activation patterns. Research has shown that prefrontal cortex (PFC) activation may be involved in both motor control and fatigue throughout the recovery process post-stroke. The aim of this thesis was to determine whether: (1) PFC activation levels change between standing balance tasks, (2) PFC hemispheric activation is asymmetric during standing balance tasks, and (3) fatigue levels are associated with task-based activation. Patients with hemiparesis were recruited from the inpatient stroke unit at Parkwood Institute. Functional near-infrared spectroscopy was applied bilaterally over the PFC to measure brain activation during balance tasks. Fatigue was assessed using the Fatigue Severity Scale (FSS). Nine patients were included. Measures of PFC activation during the semi-tandem stance showed a greater amplitude than the double-leg stance, indicating more brain activation during this activity. Participants with greater fatigue (higher score on FSS) showed more activation in the ipsilesional PFC compared to the contralesional PFC. Greater ipsilesional PFC activation may occur when performing more challenging balance positions, potentially indicating compensatory activation.
Summary for Lay Audience
Problems with maintaining balance are common after stroke since some people can have difficulties performing voluntary movements possibly due to muscle weakness or fatigue. Individuals can also experience a change in brain activation patterns as the stroke can disrupt blood flow to the affected areas. Previous research has focused on balance issues and fatigue after stroke; however, their combined effects and relationship with brain activation have not been previously examined. Prefrontal cortex (PFC) activation has been evident while learning action sequences and has a relationship with fatigue throughout the recovery process after stroke. Thus, the purpose of this thesis was to determine whether PFC activation levels change between balance tasks, if PFC activation is asymmetrical during standing balance tasks, and if fatigue levels correlate with task-based activation. Patients after stroke with weakness on one side of their body participated from the inpatient stroke unit at Parkwood Institute. We used functional near-infrared spectroscopy (fNIRS) to observe PFC activation during standing balance tasks. fNIRS uses near-infrared light to determine the oxy-and-deoxy-hemoglobin concentration in a specific region. The increase of blood flow to an area may indicate brain activation since the tissue would require more oxygen to function. Two balance tasks were used to evoke PFC activation: (1) double-leg stance (feet shoulder width apart) and (2) semi-tandem stance (one foot in front of the other). Using the oxy-hemoglobin concentration as measured by fNIRS, we determined the asymmetry of PFC activation during both tasks. We also utilized a questionnaire to quantify self-perceived fatigue levels among participants. Nine participants were included in the study. PFC activation during the semi-tandem stance, as measured by the change in oxy-hemoglobin and deoxy-hemoglobin, was higher compared to the double-leg stance. Similarly, PFC activation in the stroke hemisphere was greater during the semi-tandem stance, potentially because this task was more challenging. Individuals with higher fatigue levels also showed more PFC activation on the stroke hemisphere. Considering task-difficulty during rehabilitation may help increase activation in the PFC in the stroke-affected hemisphere, which has been linked to better recovery.
Kohli, Sarthak, "Exploring the relationship between hemispheric prefrontal cortex activation, standing balance, and fatigue in individuals post-stroke: A fNIRS study" (2023). Electronic Thesis and Dissertation Repository. 9569.