In a step towards improving rehabilitation for patients with
walking impairments, researchers from the Kennedy Krieger Institute
found that non-invasive stimulation of the cerebellum, an area of the brain known
to be essential in adaptive learning, helped healthy individuals learn a new
walking pattern more rapidly. The findings suggest that cerebellar transcranial
direct current stimulation (tDCS) may be a valuable therapy tool to aid people
relearning how to walk following a stroke or other brain injury.
Previous studies in the lab of Amy Bastian, PhD, PT,
director of the Motion
Analysis Laboratory at Kennedy Krieger Institute, have shown that the
cerebellum, a part of the brain involved in movement coordination, is essential
for walking adaptation. In this new study, Dr. Bastian and her colleagues
explored the impact of stimulation over the cerebellum on adaptive learning of
a new walking pattern. Specifically, her team tested how anode (positive),
cathode (negative) or sham (none) stimulation affected this learning process.
“We’ve known that the cerebellum is essential to
adaptive learning mechanisms like reaching, walking, balance and eye
movements,”says Dr. Bastian. “In this study, we wanted to examine the
effects of direct stimulation of the cerebellum on locomotor learning utilizing
a split-belt treadmill that separately controls the legs.”
The study, published today in the Journal of Neurophysiology,
found that by placing electrodes on the scalp over the cerebellum and applying
very low levels of current, the rate of walking adaptation could be increased
or decreased. Dr. Bastian’s team studied 53 healthy adults in a series of
split-belt treadmill walking tests. Rather than a single belt, a split-belt
treadmill consists of two belts that can move at different speeds. During
split-belt walking, one leg is set to move faster than the other. This
initially disrupts coordination between the legs so the user is not walking
symmetrically, however over time the user learns to adapt to the disturbance.
The main experiment consisted of a two-minute baseline
period of walking with both belts at the same slow speed, followed by a
15-minute period with the belts at two separate speeds. While people were on
the treadmill, researchers stimulated one side of the cerebellum to assess the
impact on the rate of re-adjustment to a symmetric walking pattern.
Dr. Bastian’s team found not only that cerebellar tDCS can
change the rate of cerebellum-dependent locomotor learning, but specifically
that the anode speeds up learning and the cathode slows it down. It was also
surprising that the side of the cerebellum that was stimulated mattered; only
stimulation of the side that controls the leg walking on the faster treadmill
belt changed adaptation rate.
“It is important to demonstrate that we can make
learning faster or slower, as it suggests that we are not merely interfering
with brain function,” says Dr. Bastian. “Our findings also suggest
that tDCS can be selectively used to assess and understand motor
learning.”
The results from this study present an exciting opportunity
to test cerebellar tDCS as a rehabilitation tool. Dr. Bastian says, “If
anodal tDCS prompts faster learning, this may help reduce the amount of time
needed for stroke patients to relearn to walk evenly. It may also be possible
to use tDCS to help sustain gains made in therapy, so patients can retain and
practice improved walking patterns for a longer period of time. We are
currently testing these ideas in individuals who have had a stroke.”
Other co-authors on this study were Pablo Celnik and Gowri
Jayaram, Johns Hopkins University School of Medicine; and Byron Tang, Rani
Pallegadda, and Erin V.L. Vasudevan, Kennedy Krieger Institute.
The study was funded by the National Institutes of Health and the Johns Hopkins Brain
Sciences Institute.
About the Kennedy Krieger Institute:
Internationally recognized for improving the lives of children and adolescents
with disorders and injuries of the brain and spinal cord, the Kennedy Krieger
Institute in Baltimore, MD serves more than 16,000 individuals each year
through inpatient and outpatient clinics, home and community services and
school-based programs. Kennedy Krieger provides a wide range of services for
children with developmental concerns mild to severe, and is home to a team of
investigators who are contributing to the understanding of how disorders
develop while pioneering new interventions and earlier diagnosis. For more
information on Kennedy Krieger Institute, visit www.kennedykrieger.org.
About the Motion Analysis Laboratory:
The Motion Analysis
Laboratory at Kennedy Krieger Institute studies performance and learning of
reaching and walking movements in healthy adults and children, and in different
patient populations including: adults and children with cerebellar damage,
adults with hemiparesis from stroke, adults with multiple sclerosis or
adrenomyeloneuropathy, children with hemispherectomy, children with cerebral
palsy and children with autism. All studies are designed to test specific
hypotheses about the function of different brain areas, the cause of specific
impairments and/or the effects of different interventions.
