James R. Lackner - US grants

DESCRIPTION (provided by applicant): Reaching for objects are a natural and common behavior. The proposed work is based on the unexpected finding in a series of preliminary studies that extremely large Coriolis forces are generated on the arm by the trunk rotation that normally accompanies reaching to laterally placed objects. Contrary to intuition, when we turn and reach for an object, the Coriolis force generated by the torso motion on the extending arm is an order of magnitude greater than the interaction forces generated during simple reaches not involving trunk rotation. This suggests that to understand normal unconstrained reaching it will be critical to understand the forces generated by truncal movements and how they are controlled. We have developed a set of paradigms designed to isolate the contribution of torso rotation to the force profiles associated with natural reaching movements. Our goal is to contribute to the understanding of human movement control by identifying the sensory and motor signals involved in the representation of self-motion used for a) generating anticipatory compensations to maintain movement accuracy despite self-generated Coriolis forces, b) generating on-line compensations, and c) allowing adaptation plasticity for self-generated Coriolis torques. In Aim 1, we propose to determine the role of vestibular signals in compensations for interaction torques during natural turn and reach movements. In Aim 2, we will assess the role of vestibular signals in on-line compensations for interaction torques generated by reaching movements during passive rotation. In Aim 3, we will assess the plasticity of compensation for interaction torques during turn and reach movements. The experimental program will involve kinematic measurements of the arm segments for reaching movements made during both voluntary and passive torso rotation. The associated joint torques will be computed through inverse dynamics modeling. The results will provide a better understanding of the interaction forces associated with natural reaching movements involving simultaneous movements of the whole body and of how they are controlled. We will learn how the nervous system parcels the net force field into a subcomponent mechanically caused by self-rotation and maintains sensory-motor adaptation attuned to this type of load component. The results should have broad significance for normal movement control as well as for disorders of movement control.

The goal of the proposed work is to enhance the feasibility of using virtual environments (VE) for the teaching of science, technology, engineering and mathematics (STEM) at all grade levels in order to maximize the effectiveness of curricula. In principle, the applications of VEs for training in physics, chemistry, astronomy, engineering, biology and mathematics are unlimited. However, in practice, their usefulness has been limited by undesirable side effects of motion sickness, dizziness, and postural instability. Consequently, users spontaneously limit their head and body movements in frequency and amplitude and move more tentatively. Many have to terminate participation. In order for VEs to be a viable tool for educators it is necessary first to identify the primary factors that contribute to motion sickness, postural instability and impaired eye-head coordination in VEs. A coordinated series of experiments is proposed using as a model an educational VE designed to teach molecular and chemical structure. The relationship of field-of-view, tracking delays in scene updating, and visual resolution to these side effects will be determined. Techniques involving various types of haptic cuing of body and environment orientation will be used to suppress side effects and increase the user?s mobility and ability to learn the VE. Head movement contingent blanking of the visual field will be tested as a way of attenuating motion sickness, postural instability, and preventing derangements of gaze control. The goal of the proposed research is to enable students to move naturally and freely while exploring the VE without restricting their activities and without their becoming nauseous, dizzy, or unstable. Achieving this would be transformative by increasing the usefulness of immersive VEs for training in STEM disciplines.

Complexity science involves the study of situations where the behavior of a system is not easily understood by studying its parts in isolation, but depends crucially on understanding how the parts interact (the weather, turbulence, and the economy are among the most familiar examples of complex systems). Complex systems analysis has been increasingly successfully applied by psychologists and neuroscientists to the study of perception, action, and cognition. The NSF-funded research project by psychologists James Lackner and Paul DiZio at Brandeis University is an example of the application of complexity science to human movement and motor control.

Lackner and DiZio take the approach of beginning with a deceptively simple question, study it in a deceptively simple experimental paradigm, and analyze the task and behavior with a deceptively simple model. The question is how far must a person be moved off-balance before they will take a step to avoid a fall. With the Hold & Release (H&R) technique, the experimenter applies a small force to the sternum of the research participants, which they resist in order to maintain balance. When the force is released participants must make postural adjustments to maintain balance and if the force is large enough a step is required. It appears that a (relatively) simple linear model -- the one-leg inverted pendulum model -- can account for participants' postural adjustments in this situation. The model breaks down, however, when the force is large enough to require the participant to take a step in order to maintain balance. This requires the transition to a more complex non-linear model which assumes the two legs operate in a coordinated but asymmetrical fashion. Lackner and DiZio will test this model by performing the H&R task in a rotating room. This simple next step adds additional forces (especially rotational Coriolis forces that serve to pull the movement away from the intended trajectory but that change continuously as a function of the limb's velocity) and additional degrees of freedom for participants' responses that provide a rigorous environment for testing the new model. The model is refined enough to make detailed predictions about participants' stance, about which combinations of forces will push them to the stepping threshold, and even with which foot the step will be made.

If successful, Lackner and DiZio will have succeeded in taking a major step towards unifying the study of posture and locomotion, which until now have been studied as essentially separate processes. It is clear that any improvement in our understanding of motor control can have implications for the assessment and treatment of movement disorders, but this approach is particularly promising because H&R measurements are easy to make and the detailed model is so tightly coupled to the measurement paradigm. The interdisciplinary nature of complex systems research is also demonstrated by this project, in which psychologists Lackner and DiZio will employ a Ph.D. physicist as a post-doctoral researcher. Undergraduate physics majors regularly assist with Lackner and DiZio's research.

An essential issue in the movement sciences is to understand how people maintain upright posture and balance. In everyday life, people often simultaneously turn and reach to pick up objects or to place objects. Such movements are typically accurate and seem virtually effortless. However, when an arm movement is made during ongoing trunk rotation large inertial forces are generated on the reaching arm. These forces are so large that huge errors in reaching and destabilization of posture would occur if the central nervous system (CNS) did not take them into account. In this program of research, two series of experiments will examine the interaction of the control of self-rotation and of arm-torso dynamics. Series 1 will evaluate the kinematics of reaching and turning, postural sway, arm joint torques, and ground reaction forces at the feet. Series 2 will assess these variables in tasks involving active and passive torso rotation and reaching. The results will indicate whether the CNS control of trunk rotation and arm reaching are a) parallel and independent, b) hierarchical with information about intended trunk rotation contributing to separate control of torso and arm movements, or c) distributed with a single internal model for reaching and turning.

Falling in the elderly is a major health problem. Neurological diseases that affect torso and or limb movement control (e.g., Parkinson's disease) also increase the likelihood of falls. This research should provide a scientific basis for developing rehabilitation strategies that compensate for trunk-generated forces on the limbs and minimize the likelihood of falling.

Motion sickness has always accompanied the introduction of new transportation and display technologies. Although the active drivers of vehicles are usually less susceptible to motion sickness than the passive passengers, the development of self-driving cars (autonomous vehicles) makes all of the occupants passengers. One benefit of autonomous vehicles is that they free passengers to perform many activities typically done at their homes or offices. Unfortunately, when these activities require focused visual attention, such as reading, working, or watching videos, the likelihood of experiencing motion sickness increases. The goals of the current project are to identify the key factors that contribute to motion sickness in autonomous vehicles, to identify factors that characterize who will be most susceptible, and to develop ways to reduce motion sickness and declines in performance.

The project will evaluate three aspects of individuals' responses to stimulation that might provoke motion sickness: 1) the initial sensitivity to a stimulus, 2) the decay of motion sickness severity following discontinuation of stimulation, and 3) the rate of adaptation following repeated stimulation. Of key concern is whether for a given individual, initial sensitivity, decay, and adaptation will be consistent across different types of sickness-inducing stimulation. The approach is based on a mechanistic model of motion sickness derived from neurophysiological and behavioral evidence concerning the relationship between motion sickness onset and disruptions of vestibulo-ocular and vestibulo-motor control. The role of active control of forthcoming stimulation (the fact that the driver rarely becomes motion sick) will be systematically evaluated to determine the extent to which anticipation plays a role in sickness prevention. The investigators will compare initial sensitivity, decay, and adaptability of motion sickness across stimulation involving a) the semicircular canals of the inner ear, which are sensitive to angular acceleration, b) the otolith organs of the inner ear, which are sensitive to linear acceleration, c) both in combination, and d) vision in order to assess their contributions to an individual's overall pattern of motion sickness vulnerability under active and passive conditions. The aim is to develop predictors of an individual's sensitivity to the factors contributing to motion sickness in autonomous vehicles (control vs. no-control, frequency and amplitude dependent characteristics of vehicle motion, and focal visual attention tasks). This capability would allow remedial steps to be taken to reduce sickness likelihood and optimize the benefits of this new technology.

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.