Current Research Projects

Mechanisms of Balance Control during Locomotion

Maintaining balance during locomotion is a complex task with requirements and constraints that change during the gait cycle. To understand the control actions employed by the central nervous system (CNS) to achieve this, we induce illusions of falling and observe how the motor system responds. We prefer sensory perturbations to induce illusory falls rather than mechanical perturbations to induce real falls, because in the latter case it is hard to distinguish between purely mechanical, passive effects of the perturbation on the body and active responses from control action taken by the CNS.

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Sub-Concussion and Balance Control

Sub-concussion is a cranial impact that does not lead to clinical symptoms. Current thinking views subconcussion as an under-recognized phenomenon that may cause measurable neurological injury. We have established an innovative human experimental paradigm using soccer heading to induce mild mechanical stress on brain tissue that is indicative of commonly experienced stress levels in humans experienced during sports/recreational activities. The long-term goal of this project is to investigate potential mechanisms underlying brain injury due to mild mechanical impact.

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TreadSense

Previous research investigating visual feedback and postural control has focused on static posture while subjects attempt to keep their center of pressure on a visual target on a computer screen. This method of application has been met with mixed results regarding improvements in balance ability. This may be related to the variable that is controlled by the feedback, or the method of feedback training. Moreover, most falls occur during movement or during transitions from stationary positions to moving activities. The purpose of this project is to improve balance control during walking through the use of a novel application of visual feedback. Subjects walk on a treadmill in front of a LCD TV with feedback about trunk movement displayed relative to a target. Older adult subjects with balance difficulties are recruited in an intervention consisting of 4 weeks of visual feedback training on a treadmill 3 times per week. Participants will be tested using standard clinical assessments of balance and gait pre- and post- intervention.

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ArmSense

Parkinson's disease (PD) leads to progressive movement problems that affect safety and independence, including slow walking and movement, short shuffling steps, tremor, rigidity, and balance loss. These problems may be exacerbated by sensory or processing impairments, decreasing a person’s awareness of their own movements. Therapy treatment use external cuing to compensate for this loss, but any movement improvements disappear soon after the cues are stopped. ArmSense is a portable arm swing feedback device to cue larger movements even outside the clinic, providing consistent feedback for larger movements at home and in the community.

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Sensory Processing and Balance Control during Walking in CP

The goal of this project is to characterize neural control strategies underlying walking in children with cerebral palsy (CP) to inform the development of new therapeutic approaches. In general, rehabilitation interventions focus on improving functional performance by decreasing motor deficits associated with muscle spasticity and weakness in children with CP. Far less attention has been paid to sensory processing deficits. However, recent studies have suggested that a significant contributor to the motor function deficit in children with CP may be impairment in the neural processing of tactile discrimination and proprioception information. The mechanisms associated with such sensory deficits, and how they impact motor control in individuals with CP, are unknown. The primary triad of sensory modalities that are crucial for healthy postural control are the visual, vestibular, and proprioceptive systems. We have developed innovative techniques to manipulate these sensory modalities, allowing investigation of how they support stable and flexible control of upright equilibrium during standing and walking. The long-term view is that this approach will identify mechanisms toward developing more effective sensorimotor rehabilitation paradigms for children with CP. The expected outcomes of this study include: 1) a better understanding of the relationship between sensory processing and functional mobility in individuals with CP; and 2) an elucidation of the effect of galvanic vestibular stimulation on individuals with CP. These findings may support a multi-dimensional clinical approach to potentiate typically motor-centric strategies for improving mobility in children with CP.

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Sensory Processing and Balance Control During Walking in Parkinson’s Disease

Parkinson’s disease is characterized by its progressive movement problems, but deficits in sensory function and processing can exacerbate these problems and have a negative impact on balance and function. By using movements of an immersive visual scene and electrical stimulation to the vestibular system, we can provide sensory stimulation that challenges a person’s sense of balance. We can then track and quantify the balance response through infrared motion-capture video, pressure on a force plate, and electromyographic (EMG) activity. To understand these deficits in the larger context of function and rehabilitation, we look for relationships between balance responses and self-reported balance confidence and quality of life.

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Balance During Obstacle Avoidance

Injuries from falls are a major public health issue. Falls often occur when the environment restricts the range of possible movements and drives the walking human out of the safety zone into less stable behavior. We use obstacles obstructing a walkway as a basic model of interactions between the balance system and environmental constraints. Stepping over an obstacle is a complex behavior, with a multitude of different aspects such as horizontal distance to the obstacle before and after the step, vertical clearance of the ankle and toes when passing the obstacle, development of the ground reaction forces under the stance foot, and total time for stepping over. These aspects interact with each other in non-trivial ways. For instance, the total time used for a step is increased when stepping over a higher obstacle, but not when taking a longer step over a more distant obstacle. Increases in step time shifts the relative importance between the different mechanisms of balance control (link). The stance foot ankle strategy becomes more important for longer steps. Observing changes in the relevant balance responses, e.g. the stance foot ground reaction forces, provides a way to understand how the motor plans accommodate different balance requirements imposed by the environment.

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Sensor Fusion for Balance Control in Children with Cerebral Palsy

Cerebral Palsy (CP) is a group of disorders affecting the development of movement and posture and is characterized by many functional impairments of which include poor balance, difficulties in gait and deterioration of ambulatory ability over time. Traditional rehabilitation and motor learning approaches in CP are generally motor-centric focusing on techniques to ameliorate musculoskeletal and motor impairments. It is unknown if impaired somatosensory processing can be modulated in children with CP to enhance postural control. This project uses a sensor fusion paradigm to investigate potential deficits in the dynamic integration of visual, vestibular and proprioceptive modalities that contribute to balance. Stochastic resonance (SR) stimulation, which has been shown to reduce postural sway in individuals with proprioceptive deficits, will then be used to potentiate the effects of existing treatment strategies for improving balance and motor control.

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