In partial fulfillment of the requirements for the degree of

Doctor of Philosophy in Applied Physiology

In the

School of Biological Sciences

Bennett Alterman

Will defend his dissertation

Neuroplasticity and Upper-Limb Loss: Towards Predicting and Improving Functional Rehabilitation Outcomes 

Monday, July 18, 2022

8 AM

In-Person: Applied Physiology Building, Room 1253

555 14th St NW, Atlanta, GA 30318

Virtual: https://gatech.zoom.us/j/95369297663

 Thesis Advisor:

Lewis Wheaton, Ph.D.

School of Biological Sciences

Georgia Institute of Technology

Committee Members:

Young-Hui Chang, Ph.D.

School of Biological Sciences

Georgia Institute of Technology

Boris Prilutsky, Ph.D.

School of Medicine

Emory University

School of Biological Sciences

Georgia Institute of Technology

Michael Borich, Ph.D.

School of Biological Sciences

Georgia Institute of Technology

Leonardo Cohen, M.D.

National Institute of Neurological Disorders and Stoke

National Institutes of Health

ABSTRACT: Reaching and grasping is so universally integrated into our daily activities that we can perform it almost without thought. We can grasp a cup of coffee while thinking about what we want for breakfast, listening to the morning weather report, and mentally preparing ourselves for work that day. Unfortunately, reaching and grasping is not so simple for persons living with upper-extremity amputation. We are often unaware of the ability of our brains and bodies to coordinate the movement dynamics and sensory information coming from interacting with the environment to produce efficient and effective actions. A disruption in the peripheral nervous system (e.g., amputation) means the typical neural and kinematic patterns of activation formerly used are no longer up to date. With the loss of part of the hand (partial-hand amputation) or the hand and forearm (transradial amputation), individuals must create new patterns as they learn to control a prosthesis, creating an altered state which presents challenges to interacting with and manipulating objects, often leading to device abandonment.

There is great variability in motor behavior using upper-extremity prostheses for different levels of amputation, leading to challenges in interpretation of ideal rehabilitation strategies. Elucidating the underlying neuromotor control mechanisms driving this variability will be beneficial to our understanding of human adaptation after limb loss. The purpose of this thesis is to evaluate the neurobehavioral mechanisms underlying the adaptation to updated motor demands placed on the upper extremity after transradial or partial-hand amputation. In particular, I am examining how training one limb may induce changes in brain organization and behavior corresponding not only to the trained limb, but to the untrained limb as well (“interlimb training”), and how factors like device level and action variability may mediate the efficacy of this training. 

Aim 1 demonstrated that device level and task complexity mediate grasp posture selection and variability, leading to changes in functional performance outcomes for non-amputated individuals adapting to prosthesis simulator use. Aim 2 validated these findings by showing neural adaptation in the sensorimotor cortices is also mediated by device level and task complexity, exhibiting activation patterns ipsilateral to device use, unlike the predominantly contralateral motor control networks in sound limb individuals. Aim 3 introduced interlimb training, and found that transfer of skill between limbs does occur, and may be modulated in a task- and device-dependent manner similar to Aims 1 and 2, providing possible factors to predict the efficacy of interlimb training in rehabilitation. Through the implementation of a multimodal approach, these results provide quantitative insights into functional and neural adaptation processes, which can be used to inform and improve rehabilitation practices for persons with upper-extremity amputation.