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).

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.

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.

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

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.