Voluntary eyelid contraction modifies the blink reflex recovery cycle.
In order to determine the extent to which the recovery cycle of the blink reflex is modified by voluntary contraction of the eyelids we investigated the electrically elicited blink reflex with paired stimuli of identical intensity in 9 healthy subjects. We pseudorandomly administered two interstimulus intervals (150 ms and 250 ms) in three different conditions of voluntary contraction of the orbicularis oculi muscle (relaxed, mild lid closure and strong lid closure). Our results show that inhibition of the R2 response following the second stimulus is significantly reduced with voluntary contraction. In addition, we found significantly larger amplitudes and shorter latencies of R1 and R2 with voluntary contraction. We conclude that in healthy subjects, voluntary eyelid contraction causes facilitation or disinhibition not only in the nuclei of the seventh cranial nerve, but also in the polysynaptic pathway of the R2. The possible implications on the interpretation of clinical data are discussed.
Department of Clinical Neurophysiology, Center for Neurological Medicine, University of Göttingen, Germany.
M
M
Sommer
G
G
Wöbker
A
A
Ferbert
D000328:Adult; D000368:Aged; D001767:Blinking / Q000502:physiology*; D004558:Electric Stimulation; D005154:Facial Nerve / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000502:physiology*; D009433:Neural Inhibition / Q000502:physiology; D012016:Reference Values; D012032:Refractory Period, Electrophysiological / Q000502:physiology*; D013569:Synapses / Q000502:physiology