NSF Award
1803714
The vast majority of research in cerebral palsy (CP) involves children who have the ability to stand and walk. In contrast, children with severe CP, who do not have the ability to walk, are typically excluded from activity-based research or are studied in very simplistic or nonobjective ways. This project will focus on understanding the complex task of trunk posture control in children with severe CP. Trunk posture control underlies nearly all motor activities, including speech, eating, and socialization. This project uses control systems engineering in an innovative way to determine which neural processes are intact, delayed, or absent in individual children with severe CP. Furthermore, while posture models exist for adults who have the ability to stand, no model exists for individuals who lack independent sitting or for children with CP. The researchers will develop and validate models that quantify specific neural systems in posture control. These models help identify underlying mechanisms used by children with CP when attempting to control their balance. The development, refinement, and testing of models will be a major advance in clinical engineering, in that the quantification of model parameters, e.g., joint stiffness and neural time delay, will have immediate and fundamental implications on clinical practice. Educational activities associated with this project will engage students with and without CP who are in high school, undergraduate, and graduate school. In addition to learning about posture control, students will learn about modeling and control systems. Finally, students will be engaged in creating and testing a unique dissemination tool, "sim CP." In "sim CP," typically developing children and adults can attempt to control their posture while constrained by the computer simulation to adjust to CP-like challenges on motor outcomes. Together, this research project will catalyze the field by combining engineering, parametric modeling, and clinical pediatrics to investigate posture control in children with severe CP with the added impact of mentoring students and creating novel dissemination tools.<br/><br/>Due to the inherent complexity of closed loop posture control, it is difficult to identify neural processes underlying healthy posture sway. This difficulty is exacerbated in children with severe CP who lack independent sitting, and who may also have abnormal tone or lack of verbal communication. This project overcomes these barriers by leveraging controls engineering to probe the posture system of children with moderate-to-severe CP. The Research Plan is organized under three objectives. The first objective is to characterize the posture system and potential for learning by collecting a rich experimental data set of posture behavior. Participants sit on an articulating bench with an adjustable trunk system that moves synchronously with surface tilts with high resolution and accuracy. The support stabilizes specific segments of the trunk in vertical upright alignment while requiring static, active and reactive posture control above the supported segments. Posture responses will be evoked with custom external stimuli: sine waves, pseudorandom waveforms, and a novel sitting sway-referenced condition to examine motor learning. Data will be collected with two different levels of trunk support: the lowest level where trunk control is present and one level lower where control is challenged. The second objective is to develop experimentally-valid parametric models of the posture system that explain sway data across frequencies from approximately 0.04 to 1.5 Hz. The posture model will identify underlying systems and control mechanisms, such as neural time delays, sensorimotor noise, sensory-to-motor transformations, joint stiffness and damping, and adaptation of control parameters. Different model assumptions (based on existing motor control research) will be tested. The third objective is to compare results in 15 children, ages 6 to 17 years old with moderate to severe CP (Gross Motor Function Classification Scale levels IV & V), to age-matched controls using the same experimental and modeling techniques.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
