Modulation of the electrically evoked blink reflex by different levels of tonic preinnervation of the orbicularis oculi muscle.
Eleven subjects were instructed to maintain different levels of tonic pre-innervation of the two orbicularis oculi muscles: relaxation, 25%, 50%, 75% and 100% of maximum voluntary contraction. Surface electromyographic activity was recorded unilaterally from the left orbicularis oculi muscle while cutaneous reflex responses were evoked electrically during different levels of pre-innervation. Latencies of the early (R1) and late (R2) blink reflex responses were significantly shorter during moderate pre-innervation level (25%) compared to relaxation, with no further latency decrease under stronger tonic pre-innervation. The amplitude of the R1 component increased significantly until a pre-innervation level of 50% of maximum voluntary contraction was reached. There was no further amplitude enhancement with stronger pre-innervation. R2 amplitudes linearly increased with the increasing pre-innervation levels, possibly reflecting recruitment of a greater number of motor units for the late component or a postponement of motoneuron synchronization of the late component.
Jäncke
L
L
Institute of General Psychology, Heinrich-Heine-University, Düsseldorf, FRG.
Bauer
A
A
von Giesen
H
H
D000328:Adult; D001767:Blinking / Q000502:physiology*; D004558:Electric Stimulation; D004576:Electromyography; D005260:Female; D006801:Humans; D008297:Male