John Jeka - US grants

Human standing posture is inherently unstable; even when one is standing quietly, small disturbances and corrections of posture occur continually. Control of human upright stance requires sensory input to perceive the distinction between movements of one's own body and movement of the environment. These inputs include (1) visual information from the eyes; (2) vestibular (inner ear) information about head orientation; and (3) somatosensory (touch) information about position of body segments and external surfaces, from receptors in the muscles and skin. Most postural control studies have focused on isolating a particular sensory input through experimental manipulation or pathology (e.g., patients without a functioning inner ear), to determine how an individual sensory input influences postural control. However, a single input rarely works in isolation and there is a need to understand how multiple inputs interact. The present study analyzes human postural control while simultaneously manipulating two sensory inputs, vision and touch. Previous studies have shown that vision can influence postural sway: A person standing quietly in front of a moving visual pattern sways at the frequency of the visual display. More recently, experiments in our lab have shown that the sense of touch can similarly influence sway. Postural stability was enhanced when people lightly touched a rigid surface with a single fingertip; and, if the touched surface was moving, postural sway assumed the frequency of the moving surface. The intent of the present study is to provide visual and touch information simultaneously, to determine how these two sensory inputs interact in the control of postural sway. Individuals will stand in front of a visual display consisting of a random dot pattern. At the same time they will touch a rigid metal plate. The experiments will explore how postural sway is influenced when 1) visual cues are moving and touch cues are static, and vice versa; and 2) visual and touch cues are both moving. The question is whether postural responses are dominated by vision or touch, or whether instead a more complex relationship obtains. These studies should lead to a better theoretical understanding of how the central nervous system processes complex sensory information, and eventually to better rehabilitative techniques for patients who have lost sensory function due to neurological injury (e.g., stroke).

DESCRIPTION (provided by applicant): The long-term goal of this research is to understand how the nervous system combines information from multiple senses for the control of multisegment human upright stance. Imbalance is a major cause of fall- related injuries, whose cost to the health-care system is expected to exceed $32B by 2020. Current interventions to improve balance and reduce the risk for falls lack a theoretical framework because the mechanisms by which they affect postural control processes are not well understood. Until the control processes underlying a balance deficit are understood, rehabilitative programs will continue to intervene in costly and time-consuming non-specific ways. This proposal emphasizes an experimental strategy designed to probe the underlying postural control loop in patient populations with far more certainty than present methods. Ten experiments will investigate three specific aims. I. To identify open-loop frequency response functions characterizing multijoint postural control. II. To investigate the dynamics of intermodality reweighting. III. To investigate the adaptability of the multijoint control strategy in bilateral vestibular loss (BVL) patients. We propose to build on the findings from previous grant cycles focusing on the properties of multisensory reweighting by manipulating different combinations of two sensory inputs. In addition, we will expand a system identification technique previously developed for single-joint postural control. Multiple, simultaneous, mechanical and sensory perturbations will identify how muscular activity translates into control of body segment positions (the plant) and how, in turn, body segment positions translate into new muscular activity (feedback). This identification will be achieved within the context of the multi-joint body, whose relative configuration must be incorporated into the estimate of body dynamics. Finally, healthy and bilateral vestibular loss individuals will be compared with these identification techniques to determine how loss of vestibular function disrupts the plant and feedback control loops. With such knowledge, rehabilitative efforts may then emphasize methods that focus on a particular process within the control loop to optimize rehabilitation, leading to more effective, targeted care and reduction of health care costs. PUBLIC HEALTH RELEVANCE The long-term goal of this research is to understand how the nervous system fuses information from multiple sensory systems for the control of multisegment human upright stance. The significance to society is that the neural/biomechanical systems involved in bipedal balance are subject to injury and dysfunction, leading to poor balance control with limited treatment options. Imbalance is a major cause of falls and in older adults is strongly associated with functional decline and frailty. The cost to society is enormous. Total costs of fall injuries for people 65+ in 1994 were $20.4 B and are expected to exceed $32B by 2020, leading Congress to institute legislation expanding fall-related research and fall-risk reduction programs (House Resolution 3695, 2002).

The overall goal of this research is to understand the relationship between
perception and action in the development of infant postural control.
Although the development of posture and locomotion has been well
documented, only recently has an understanding of the processes that
underlie these changes been sought. This project examines
perception-action coupling as one of the processes that may contribute to
the observed changes. The research is designed to examine the relationship
between perception and posture in three ways. First, we propose to study
infants' postural development longitudinally from the onset of sitting to
three months after the onset of independent walking. Second, we focus on
the role somatosensation plays in postural control. And third, we measure
the coupling relationship between somatosensory input and the infant's
postural responses. Infants will be tested sitting and standing in one of
3 conditions: touching a fixed bar with the hand, no touch (hands free),
or touching a gently moving bar. Relationships between the excursions of
the head, center of mass, and center of pressure as well as forces applied
at the hand will be analyzed. Data are expected to provide critical
information about the study of normal infant postural development as well
as to lay a foundation for understanding those infants with abnormal or
delayed postural development.

DESCRIPTION (provided by applicant): The long-term goal of this research is to understand how the nervous system fuses information from multiple sensory systems for the control of upright stance. The ability to select and reweight alternative orientation references adaptively is considered a critical factor for postural control in patient and elderly populations. Despite the importance of multisensory reweighting, little is known about how it is achieved. We have developed a new experimental paradigm that simultaneously manipulates two sensory inputs (vision and touch) to probe the properties of multisensory integration. In parallel, we have developed a unique two-step modeling approach using time series techniques and mechanistic models to determine which characteristics of postural sway can: i) be attributed to estimation or control; and ii) distinguish different mechanisms of estimation used for multisensory reweighting. Here we focus on modeling the process of multisensory reweighting in changing sensory environments. The goal is to develop a mechanistic model that will explicitly link underlying physiological subsystems to postural control. Future work will address patient populations with similar techniques to determine the basis of their balance deficits.

The PIs propose to establish a five-year ITR program that will lead the development of the next generation distributed video sensing systems for understanding human movements. Novel models of human movement and structure will be used for modeling the movements of singe-joint and whole bodies with applications to animation, biomotion, and gait analysis for diagnosing and treating movement-related disorders. The interdisciplinary team includes leading researchers from three core institutions - the University of Maryland (lead institution), Stanford University and New York University. The researchers cover a broad spectrum of interests, including biomechanics, computer science and engineering, electrical engineering, and kinesiology. The proposed research efforts will enable novel approaches for realistic animation and the detection of subtle variations in movement, leading to better diagnostic tools and personalized programs for rehabilitation of movement disorders. Strong educational and industrial outreach programs will also enhance our research program.

[unreadable] DESCRIPTION (provided by applicant): This project is to support an international and interdisciplinary research conference on the most current research on balance, gait and associated disorders with applications to rehabilitation and clinical practice. The conference will focus on four specific themes: 1) vestibular mechanisms; 2) aging; 3) neurological disorders; and 4) rehabilitation. The significance to society is that the neural/biomechanical systems involved in balance and gait are subject to injury and dysfunction, leading to poor control of upright stance with limited treatment options. By bringing together scholars who investigate balance/gait and mobility problems, and focusing on how basic research is furthering clinical practice, progress will be made in understanding and remedying the difficulties that older adults and patient populations experience with motor behaviors that play a fundamental role in the quality of everyday life. Poor balance is a major cause of falls in older adults and patient populations and is strongly associated with functional decline and frailty. The cost to society is enormous. Total costs of fall injuries for people 65+ in 1994 were $20.4 B and are expected to exceed $32B by 2020, leading Congress to legislation expanding fall-related research and fall-risk reduction programs (House Resolution 3695, 2002). We argue that a better understanding of the processes underlying the control of posture and locomotion will enhance the treatment options presently available. [unreadable] [unreadable] [unreadable] [unreadable]

The evolutionary development of bipedal stance, which freed the hands from locomotion, is considered a fundamental distinction between humans and our closest relatives. Accompanying that development was an increase in instability of the body. Engineered devices such as cars and robots typically solve the stability problem by having a wide base of support and/or having the bulk of the weight concentrated lower down. However, the human body has a narrow base of support and most of its mass is concentrated higher up in the trunk, making us inherently unstable and prone to falls. This project brings both experimental and sophisticated nonlinear analysis techniques to bear on the question of how the stability of human bipedal locomotion is achieved.

Locomotion is a critical daily life activity. Our living environment is structured to be compatible with the scale and manner with which humans move. Despite attempts to restructure the environment, people who have limited mobility and are forced to navigate with assistive devices such as crutches or wheelchairs still encounter many obstacles. A better understanding of how we interact with the environment for upright stability has implications for improving human mobility of all kinds and hence quality of life. The investigators also foster participation of undergraduate and high school students in the research through established programs at the University of Maryland and Montgomery Blair High School. By targeting ethnic and racial groups currently underrepresented in science, the project makes significant contributions to the integration of research, training and education.

This work is co-funded by SBE/BCS and the Office of International Science and Engineering

Walking for a healthy adult seems easy. However, underlying this apparent simplicity our nervous system is performing a task of astounding complexity. Using sensory information about body movement, the nervous system coordinates the activation of dozens of muscles so that we stably and efficiently move through our environment. For example, if our nervous system senses that our foot will strike the ground too soon, it will adjust muscle activations so we do not stumble and fall. In this project, an interdisciplinary team of investigators aims to uncover the rules the nervous system uses to make such adjustments. Using a general theoretical framework taken from engineering (used to understand, for example, the rhythmic control of the angle of attack of rotating helicopter blades), the method depends on gently perturbing a person's senses and body in various ways and observing how the nervous system adjusts muscle activations in response. The investigators will first test their methods on a simpler type of rhythmic movement, repetitive hitting of a virtual ball with a paddle, then extend the findings to coordination during walking.

By constructing a general approach to understanding the control of rhythmic movements, including swimming in fish, flying in insects and birds, and walking in people and robots, the investigators may provide a foundation for understanding how control breaks down for people with neurological conditions such as stroke and incomplete spinal cord injury. This has the potential to advance neuromuscular rehabilitation and the design of assistive devices.

[Co-funded by CISE and SBE]

The long-term goals of this project are to determine how repeated, subclinical brain stress may lead to clinically significant brain damage, and to use this knowledge to prevent cumulative neurological disability. Sub-concussion is an under-recognized phenomenon, in which cranial impact does not lead to clinical symptoms, but when repeated frequently, can cause measurable neurological dysfunction in athletes and others engaged in activities that introduce mild mechanical stresses to the brain. Little is known about how brain tissue injury develops and resolves at the cellular level in these cases because no individual episode of physical trauma is sufficiently strong enough to cause outwardly observable concussion symptoms. Such sub-concussive blows occur frequently during the course of normal play (blocking in football, heading in soccer, etc.). However, without obvious clinical signs, underlying neurological damage goes unnoticed, players return to play and damage can accumulate over time. The proposed project is based on the premise that mild mechanical impact introduces brain stress unobservable by self-examination, or common diagnostics, but detectable by specialized behavioral tests and cutting-edge extracelluar vesicle analysis techniques. Such techniques could determine when it is safe or dangerous to resume the activity. Using soccer heading to induce mild mechanical stress on brain tissue, we have established an innovative human experimental paradigm that is indicative of commonly experienced stress levels during sports/recreational activities. With this paradigm, we will develop new tools to characterize the neurological effects of sub-concussive impact. In Aim 1, we will quantify behavioral effects of mild head impact using sensitive measures of postural stability during standing and walking. In Aim 2, we will determine a circulating molecular pattern of subconcussive head injury using an innovative technique for blood brain barrier- and CNS cell-derived microvesicle profiling. In Aim 3, we will identify a unique microRNA signature of subconcussive head impact in circulating exosomes using cutting-edge sequencing technology. The proposed study is innovative because it will introduce an entirely new dimension to the pathophysiology of subconcussive head impact. Results of this project will potentially lead to the development of innovative behavioral and molecular diagnostic tools to assess risk of cumulative brain injury.