Enhancing sensorimotor control: exploring stochastic resonance electrical stimulation in individuals with and without cerebral palsy during the timed up-and-go test

Abstract

Sensory insufficiencies are present in about 90% of individuals with Cerebral Palsy (CP), mainly affecting senses such as touch, pressure, two-point discrimination, stereognosis, and proprioception. Somatosensory deficits contribute to balance impairments and postural challenges, leading to a poorer quality of life in individuals with CP. However, there is a lack of effective sensory-motor interventions necessary to enhance somatosensory perception and balance. Enhancing weak sensory signals through Stochastic Resonance (SR) electrical stimulation may improve somatosensory capacity in individuals with CP. SR stimulation has shown promising results for improving balance during standing and walking in children with CP. It can be inferred that improvements in balance may result from improved somatosensation. However, the direct effect of SR on somatosensation has been underexplored. ☐ In aim 1, I investigated the immediate effects of SR on lower extremity somatosensation in individuals with and without CP. I found that individuals with CP exhibit greater ankle and hip joint position errors and impaired two-point discrimination at the thigh compared with the typically developing (TD) group. SR improved somatosensation in three of the four somatosensory tests conducted for both the CP and TD groups. The improvements in somatosensory tests in both groups imply that SR may modulate somatosensation regardless of the presence or absence of underlying pathology. ☐ Thirty-five percent of falls in individuals with CP occur during walking-related activities such as turning and trunk bending, which are components of the TUG. While SR has shown promising results in improving balance during standing and walking in individuals with CP, its effect on a more complicated task, such as the TUG, is unknown. Therefore, in aim 2, I evaluated and compared Timed Up and Go Test (TUG) performance in individuals with and without CP. I segmented the TUG into five phases, i.e., sit-to-walk, walk forward, turn, walk back, and turn-and-sit, and evaluated the time required to complete the overall TUG and each phase. Additionally, I examined the center of mass and center of pressure trajectories, spatiotemporal metrics, body kinematics, and kinetics using z-score distributions. I found that individuals with CP took longer to complete the TUG and its phases than the TD group. Further exploration revealed spatiotemporal deficits for the CP group, including a greater number of steps, reduced step length, increased step width, and reduced COM velocity during walking and turning phases compared to the TD group. ☐ The findings suggested that the TUG may have the ability to differentiate between individuals with CP and TD not only based on the time to completion measure but also by the spatiotemporal and COM velocity measures. This work showed a significantly longer time to complete the TUG and greater variation in z-score distributions in the sample with CP compared to the TD sample. With recent technological advances, TUG segmentation into its phases and biomechanical evaluation of performance in these phases may be possible using smartphone or inertial sensor applications. Further exploration is needed to identify the most important measures that can be easily computed in a clinical setting to characterize performance and change during each phase of the TUG. ☐ Finally, in aim 3, I investigated whether improved proprioception due to SR could lead to immediate changes in TUG performance in individuals with CP. In this study, I did not observe any improvements in the time to complete the TUG, or any of its phases with the use of SR. I propose that the somatosensory influences didn’t translate into motor impairments because of lower-extremity muscle weakness and spasticity in individuals with CP, which can still impair TUG performance time, even when individuals receive augmented proprioceptive information. Additionally, improved proprioceptive information for a short span of time likely is unable to change learnt motor mechanics so quickly. ☐ Overall, the findings from this dissertation contribute to: 1) the understanding of SR electrical stimulation as a sensory-centric modality that can improve somatosensation in individuals with and without CP; 2) guiding researchers and clinicians in utilizing the TUG as more than a time metric to assess functional motor impairment in individuals with CP; and 3) adding to the knowledge that SR might not lead to immediate changes in functional performance. SR may be more beneficial when combined with a long-term training program that involves repetitive use of enhanced somatosensory input and strength or gait training.