Expertise:
Robotics,
control theory, neuromechanics
Hand impairment is the most common chronic motor impairment
following stroke. With upwards of 700,000 strokes occurring
annually in the U.S. alone (Broderick, et al. 1998) , this
is a significant problem. Surprisingly, though, diminished
motor control of the hand following stroke, cerebral palsy,
or other similar insults has not been studied as widely as
one might expect. Thus, for the past several years I have
been conducting research in this area and plan to continue
this work in the future. I have been interested in rehabilitation
since the beginning of my graduate studies.
My current research has three main thrusts. The first entails
a detailed analysis of the underlying mechanisms of impairment.
This necessitates a second research area to describe how
the hand functions when unimpaired. The final area uses the
knowledge gained in the other two areas to develop devices
and techniques to assist treatment or function.
The true mechanisms of impairment may be difficult to detect
as they result from secondary changes derived from the original
brain infarct. As animal models of chronic stroke are difficult
and rare, one must probe human subjects directly, thereby
requiring less invasive methods and system identification
techniques. Our group has been employing controlled mechanical
perturbations and electrical stimulation to explore underlying
changes in passive tissue, reflexive behavior, and motor
control.
To date, we have detected spasticity in the flexor (but
not extensor) muscles of the fingers, involuntarily sustained
activation of the flexors, and excess coactivation of the
flexors and extensors. The asymmetry of the responses of
the flexors and extensors is much greater than that reported
at other joints following stroke and quite different from
the presentation following complete spinal cord injury. We
are thus exploring potential contributions from the brainstem,
with the hope that involved neuromodulators are susceptible
to pharmacological intervention.
Due to the complexity of the system, distinguishing healthy
from aberrant behavior often proves difficult. One example
is the true action of individual muscles, whose tendons cross
multiple joints and may even join together as is the case
in the extensor hood. In response to this and other similar
problems, we have been studying motor control in healthy
hands as well. One offshoot of this research involves the
development of a biomechanical model of the index finger.
We are collecting experimental data to estimate passive joint
mechanics and the transformation of muscle activation into
joint torque. We believe this model will allow us to pinpoint
sources of impairment as well as to predict the outcomes
of certain interventions.
The ultimate goal of this research is to assist hand rehabilitation
after stroke. Using our acquired knowledge regarding the
greater loss in extension, as compared to flexion, strength,
we have constructed externally powered devices to aid finger
extension. Clinical trials have recently been initiated to
test the efficacy of these devices as therapeutic tools to
improve hand function. Augmented reality is incorporated
into the training paradigm in order to provide target objects
that can be easily manipulated by the subjects.
Specific research projects:
-- Development of glove orthoses to assist finger extension
following stroke
-- Assessment of cortical pathways following stroke using
TMS and visual imagery
-- Neuromechanics of the fingers
-- Reflex behavior and spasticity of the upper extremity
following stroke
Laboratory personnel:
Erik Cruz (Graduate Student at Northwestern University)
e-cruz@northwestern.edu
Xun Luo (Graduate Student at University of Illinois at
Chicago)
xluo1@uic.edu
Jie Liu (Postdoctoral Fellow)
jie-liu@northwestern.edu
Joe Towles (Postdoctoral Fellow)
towels@northwestern.edu
Recent publications:
Broderick JP, Brott T, Kothari R, Miller R, Khoury J, Pancioli
A, Gebel J, Mills D, Minneci L, Shukla R. The Greater Cincinnati/Northern
Kentucky Stroke Study: preliminary first-ever and total incidence
rates of stroke among blacks. Stroke 29: 415-421, 1998.
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