The Journal of Neuroscience, March 15, 2003, 23(6):2014
BRIEF COMMUNICATION
Patterned Sensory Stimulation Induces Plasticity in Reciprocal Ia
Inhibition in Humans
Monica A.
Perez2,
Edelle C.
Field-Fote2, and
Mary Kay
Floeter1
1 National Institute of Neurological Disorders and
Stroke, National Institutes of Health, Bethesda, Maryland 20892, and
2 Department of Orthopedics and Rehabilitation, Division of
Physical Therapy, and The Miami Project to Cure Paralysis, University
of Miami School of Medicine, Miami, Florida 33136
Training of spinal cord circuits using sensorimotor stimulation has
been proposed as a strategy to improve movement after spinal injury.
How sensory stimulation may lead to long-lasting changes is not well
understood. We studied whether sensory stimulation might induce changes
in the strength of a specific spinal interneuronal circuit: spinally
mediated reciprocal Ia inhibition. In healthy humans, the strength of
reciprocal inhibition between ankle flexor and extensor muscles was
assessed before and after 30 min of peroneal nerve stimulation at motor
threshold intensity. Three stimulation protocols were assessed:
patterned nerve stimulation (10 pulses at 100 Hz every 1.5 sec),
uniform nerve stimulation (one pulse every 150 msec), and combined
stimulation of the peroneal nerve and the motor cortex with
transcranial magnetic stimulation. Short-latency reciprocal inhibition
from ankle flexor to extensor muscles was measured by conditioning the
soleus H-reflex with stimulation of the common peroneal nerve. The
strength of the reciprocal inhibition was measured at baseline and for
20 min after each stimulation session. Patterned stimulation, with or
without motor cortex stimulation, enhanced reciprocal inhibition for at
least 5 min afterward. The uniform pattern of stimulation was
ineffective. These results demonstrate the presence of short-term
plasticity within spinal inhibitory circuits. We conclude that the
pattern of sensory input is a crucial factor for inducing changes in
the spinal circuit for reciprocal inhibition in humans. These findings
may have implications for the use of repetitive patterned sensory
stimulation in rehabilitative efforts to improve walking ability in
patients with spinal injury.
Key words:
H-reflex; locomotion; transcranial magnetic
stimulation; presynaptic inhibition; spinal cord; interneurons
Copyright © 2003 Society for Neuroscience 0270-6474/03/2362014-05$05.00/0
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