title: [Function of early and late components of the blink reflex--study of discharge behavior of single motor units].
abstract: The discharge pattern of single motor units in the early (R1) and late (R2) component of the electrically evoked trigemino-facial blink reflex was investigated by means of selective EMG-recording techniques. At low rate stimulation (0,1 Hz) the stimulus threshold of motor unit discharges in R1 was clearly above that in R2. Higher stimulation rates (1 Hz) were associated with an attenuation of motor unit discharges in R2 according to the well known habituation. The same motor units, however, revealed stable discharges in R1 or even signs of facilitation. These differences of motor unit recruitment in the two components indicate that R1 cannot be simply interpreted as a protective reflex like R2. At higher stimulus intensities, the characteristical firing pattern consisted of single discharges in R1 followed by high frequency multi-discharges of the same motor units in R2. This means that the motor unit discharges in R1 do not only evoke a single twitch of the eyelids but initiate a vigorous tetanic contraction with short latency. Thus, R1 yet reveals a protective function shortening the latency of the reflex blink upon stronger stimuli on the side of the affected eye.
mesh_terms: D000328:Adult; D001767:Blinking; D001933:Brain Stem / Q000502:physiology; D004558:Electric Stimulation; D005154:Facial Nerve / Q000502:physiology*; D006801:Humans; D008875:Middle Aged; D009469:Neuromuscular Junction / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology; D011999:Recruitment, Neurophysiological; D009435:Synaptic Transmission; D014276:Trigeminal Nerve / Q000502:physiology*
vernacular_title: Uberlegungen zur Funktion der frühen und späten Komponente des Blinkreflexes--Untersuchung des Entladungsverhaltens einzelner motorischer Einheiten.