ShEEP Request for Sensorimotor Dynamic Response Measurement System

Baltimore Va Medical Center, Baltimore MD

Investigators

Abstract

Falls are by far the leading cause of accidental injury and death in older adults. The Veteran population is more severely affected by falls since it is significantly older than the overall population (45% over 65 years of age vs. 13%); and Veterans would benefit substantially more from an accurate diagnosis and treatment of balance deficits and fall propensity. Despite its importance, much is still unknown about the manner in which balance control is compromised by age and disease. This is a proposal to acquire a Sensorimotor Dynamic Response Measurement System (SDRMS) from Government Scientific Source, Inc. to measure signal processing delays, transmission delays, and the neural noise associated with the four feedback sensorimotor pathways involved in standing and walking balance, the resulting feedforward motor signals to the musculature, and the response dynamics of the associated musculature. Human balance is controlled and maintained by numerous interacting sensorimotor and musculoskeletal elements, organized into an adaptive feedback control loop. These elements communicate with one another via neural signals, and the quality of these signals constitutes an important, largely overlooked aspect of this loop’s performance. Aging, associated morbidities, and injuries not only cause the elements within this loop to deteriorate; they also increase the delays and noise associated with their neural signals. Increased transmission delays and noise will in themselves degrade balance system performance and can cause such a system to fail if they become excessive. Despite its significance, balance-related transmission delays and noise have rarely been measured and investigated in a comprehensive and systematic manner. The SDRMS addresses this gap. This information is valuable for studying vulnerable Veteran populations in that it provides quantitative measures of an individual’s balance capability. Proper assessment of the sensory function in balance requires that each modality be isolated from the others and tested independently (to prevent the confounding effects of sensory system redundancy) to determine the accuracy and sensitivity with which it detects its associated stimulus; the speed with which its signals reach the higher level processing centers of the brain, and the noise associated with its signal. The SDRMS then measures the speed with which the motor centers of the brain communicate muscle activation commands to the musculature, the noise associated with these signals, and the muscles’ resulting activation dynamic response. These measures can be compared with those of young healthy individuals with no deficits to quantify the degree of deterioration brought on by age, disease, and injury; and to track changes in balance capability over time. The system can also identify the relative contribution of specific balance system elements and the neural signals they transmit to this deterioration. Government Scientific Source, Inc. will deliver the integrated system. Assessment by the SDRMS occurs in five phases corresponding to each of its five modules. Though the modules are employed in sequence, they share individual components. Thus, it would not be possible to “break the system apart” and employ the modules as separate measurement systems. Moreover, though the individual sensory modalities and feedforward pathways are tested in isolation from one another, it is important that all the assessments be conducted contiguously, as the balance system can adapt and change in subtle ways over time.