BioKim Lab for Biomechanics and Human Rehabilitation

My long-term research goal is to develop better forms of rehabilitative interventions and assistive systems that can enable people with neurological disorders or traumatic injuries to regain their sensory or motor functions. My research aims are pursued by working to discover and understand the fundamental principles that underlie motor learning and motor control.

Motor Learning and Retention:

Motor learning is a term that encompasses several component processes, such as adaptation, plasticity depending on use, and retention. I have been investigating these processes using psychophysical experiments that focus on locomotion in healthy subjects and patients. In this way, I hope to gain a greater understanding of the mechanisms underlying motor learning, and also to develop rehabilitative strategies that accelerate and enhance the process of acquiring and retaining motor skills.

Visuomotor Adaptation of Human Locomotion with Visual Feedback Distortion:

As a form of sensorimotor learning, visuomotor adaptation refers to the phenomenon that visually guided motor behavior changes in response to visual feedback. Visuomotor adaptation, which is thought to be an implicit process and plays an important role in motor planning and execution, has been widely studied and generally involves individuals making arm-reaching movements towards a target. This has led to many findings about how the brain integrates visual information to adjust motor commands. However, less is known about how visuomotor adaptation affects and is involved in human locomotion, partly because in a typical situation, locomotion is not visually guided.

I have proposed a novel task design, called visual feedback distortion, which allows participants to adapt their gait movements to external visual feedback distortions during treadmill walking. For instance, individuals walk on a treadmill while looking at a computer screen in front of the treadmill that displays two vertical bars representing the right and left step length. A visual distortion is then applied to the vertical bars (e.g., one side of the bars gets longer than the actual length). I have been investigating (1) whether learning in this model arises due to an implicit (error-based) process, a more cognitive (explicit strategic) process, or a combination of both processes; (2) how instruction and explicit knowledge of task structure influence gait adaptation driven by this task; (3) how other conditions, such as walking speed and unilateral loading, affect gait adaptation driven by visual feedback distortion; (4) the effect of implicit adaptation on the enhancement of the amount of retention; (5) how gait adaptation may be compromised in different modalities of visual feedback.

Effects of Functional Electrical Stimulation (FES)-based Perturbation on Locomotion Adaptation:

Human locomotion is a rhythmic action, and such rhythmic actions may be controlled by deep parts of the brain and spinal cord. One characteristic of locomotion is its ability to establish a phase relationship with a perturbation (entrainment). In other words, humans show the ability to spontaneously synchronize a period of their gait cycle to that of an imposed perturbation. I have been investigating (1) whether plantar-flexion ankle movements, induced by FES, can produce a form of entrainment during treadmill walking; (2) whether electrical stimulation with minimal amplitude, enough to provide sensory feedback but not enough to produce ankle torque, would induce a form of entrainment; (3) whether a carefully designed, FES-induced perturbation procedure can lead to locomotor adaptation in terms of spatiotemporal gait symmetry.