Excitability properties were recorded from 14 volunteers following stimulat
ion of the recurrent motor branch of the median nerve in the palm. Distal s
timulation resulted in significantly lower strength-duration time constant
and lower threshold during prolonged hyperpolarization than did wrist stimu
lation in the same subjects. These differences may be geometric in origin o
r alternatively may arise from functional changes distally, particularly re
duced expression of persistent Na+ conductances and more hyperpolarization-
activated current. Excitability studies using palm stimulation provide info
rmation closer to the neuromuscular junction, where membrane properties are
preferentially affected in a variety of clinical conditions. (C) 2001 John
Wiley & Sons, Inc.