Falls due to a loss of balance are a primary cause of injury and death in the elderly, and a debilitating symptom of a wide range of neurological, musculoskeletal, and cognitive deficits. However, because many neural and musculoskeletal elements can contribute to balance impairments - or equivalently to compensatory strategies - it is often difficult for clinicians to evaluate the severity of balance impairments, or to identify their underlying causes. The objective of this project is to understand the principles governing the modulation of feedforward and feedback neuromechanical elements contributing to postural stability during standing balance control. We have chosen to study the neuromechanical elements that can be rapidly modulated or selected by the nervous system, within the time frame of one session of data collection. We define feedforward neuromechanical elements to be those that adjust the intrinsic mechanical stability of the musculoskeletal system in anticipation of a postural perturbation, such as postural configuration and postural muscle tone. We define feedback neuromechanical elements to be those that activate muscles reactively following postural perturbations, and include task-level feedback gains, muscle synergies, and spinal reflexes. We hypothesize that the feedforward and feedback neuromechanical elements are modulated to achieve implicit performance goals such as stability, maneuverability, energy minimization, or robustness to uncertainty. Differing performance goals could explain variations in movement observed across trials, across individuals, across contexts, or across motor deficits. We predict that various combinations of neuromechanical elements may produce qualitatively similar movements, and yet quantitatively different functional and energetic consequences. We will study interactions between feedforward and feedback neuromechanical elements for standing balance control in normal and neurologically-impaired cats in Aim 1;during short- and long- term postural adaptations in intact animals in Aim 3.
In Aim 2, we will identify tradeoffs between functional and energetic costs and constraints that may drive postural adaptations in both health and disease using neuromechanical models of postural control. This proposal continues our development of a general scientific framework toward our long-term goal of understanding, diagnosing, and predicting optimal motor function in individuals with balance deficits, and motor impairments in general.

Public Health Relevance

Falls due to a loss of balance are the leading cause of injury leading to death in older adults. Loss of balance causing someone to fall can happen due to a number of neurological and musculoskeletal deficits. We will identify how specific neurological impairments alter subtle, but measurable changes in balance control. We also develop computer simulation and analysis tools that may eventually help physicians predict how best to treat balance impairments.

Agency
National Institute of Health (NIH)
Institute
Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD)
Type
Research Project (R01)
Project #
5R01HD046922-10
Application #
8675878
Study Section
Special Emphasis Panel (ZRG1-IFCN-H (03))
Program Officer
Quatrano, Louis A
Project Start
2004-04-01
Project End
2015-05-31
Budget Start
2014-06-01
Budget End
2015-05-31
Support Year
10
Fiscal Year
2014
Total Cost
$269,231
Indirect Cost
$21,185
Name
Emory University
Department
Biomedical Engineering
Type
Schools of Medicine
DUNS #
066469933
City
Atlanta
State
GA
Country
United States
Zip Code
30322
Sohn, M Hongchul; Ting, Lena H (2016) Suboptimal Muscle Synergy Activation Patterns Generalize their Motor Function across Postures. Front Comput Neurosci 10:7
Versteeg, Chris S; Ting, Lena H; Allen, Jessica L (2016) Hip and ankle responses for reactive balance emerge from varying priorities to reduce effort and kinematic excursion: A simulation study. J Biomech 49:3230-3237
Simpson, Cole S; Sohn, M Hongchul; Allen, Jessica L et al. (2015) Feasible muscle activation ranges based on inverse dynamics analyses of human walking. J Biomech 48:2990-7
Sawers, Andrew; Allen, Jessica L; Ting, Lena H (2015) Long-term training modifies the modular structure and organization of walking balance control. J Neurophysiol 114:3359-73
Ting, Lena H; Chiel, Hillel J; Trumbower, Randy D et al. (2015) Neuromechanical principles underlying movement modularity and their implications for rehabilitation. Neuron 86:38-54
Hayes, Heather B; Chvatal, Stacie A; French, Margaret A et al. (2014) Neuromuscular constraints on muscle coordination during overground walking in persons with chronic incomplete spinal cord injury. Clin Neurophysiol 125:2024-35
Bartlett, Harrison L; Ting, Lena H; Bingham, Jeffrey T (2014) Accuracy of force and center of pressure measures of the Wii Balance Board. Gait Posture 39:224-8
Welch, Torrence D J; Ting, Lena H (2014) Mechanisms of motor adaptation in reactive balance control. PLoS One 9:e96440
Chvatal, Stacie A; Macpherson, Jane M; Torres-Oviedo, Gelsy et al. (2013) Absence of postural muscle synergies for balance after spinal cord transection. J Neurophysiol 110:1301-10
Safavynia, Seyed A; Ting, Lena H (2013) Long-latency muscle activity reflects continuous, delayed sensorimotor feedback of task-level and not joint-level error. J Neurophysiol 110:1278-90

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