The Journal of Neuroscience, 2001, 21:RC151:1-4
RAPID COMMUNICATION
Long-Term Potentiation of the Human Blink Reflex
Jian-Bin
Mao and
Craig
Evinger
Departments of Neurobiology and Behavior and Ophthalmology, State
University of New York at Stony Brook, Stony Brook, New York
11794-5230
The trigeminal reflex blink is an ideal system to investigate
whether stimulus paradigms that produce long-term potentiation (LTP)
in vitro modify motor learning in humans. Presentation
of 12 trains of low-intensity, high-frequency stimuli (HFS) to the supraorbital branch of the trigeminal nerve (SO) modified subsequent reflex blinks of human subjects. When HFS occurred concurrently with
reflex blinks, the procedure potentiated subsequent blinks for >1 hr.
Combining HFS with feedback from the lid movement was critical for this
facilitation because presenting HFS immediately after the blink did not
alter subsequent blinks. When HFS preceded the blink, however, this
treatment suppressed subsequent blinks for 30 min. These effects appear
to occur within the trigeminal reflex blink circuits rather than at
motoneurons, because stimulation of the previously HFS-treated SO
evoked altered blinks in both eyelids, whereas stimulation of the
untreated SO elicited unaltered blinks in both eyelids. The modified
blink amplitude resulted from altering the response to A-fiber inputs
to the trigeminal nerve because all stimuli were too weak to activate
C-fibers. The data suggest that HFS produce LTP- and long-term
depression (LTD)-like effects on wide dynamic range neurons in
the trigeminal reflex blink circuit. The data also support the
hypothesis that LTP and LTD mechanisms play a role in adaptive
modification of human reflex blinks.
Key words:
LTP; LTD; blinking; wide dynamic range neurons; adaptive gain control; trigeminal
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