Neck muscle responses to abrupt free fall of the head: comparison of normal with labyrinthine-defective human subjects.
1. EMG responses from sternocleidomastoid (SCM) and orbicularis oculi were recorded in subjects who lay supine with their heads cradled in a sling. When the sling released abruptly, their heads fell freely. Normal and bilateral labyrinthine-defective subjects (LDs) were studied. 2. The normal response in SCM was a small burst of excitation at 22-25 ms latency, of 18 ms duration. This merged into a larger, later burst. The drop also produced eye blinks at 22-38 ms. 3. The onset of the SCM response in LDs was delayed (56-73 ms) even though the latency of their eye blinks was normal. 4. We conclude that the early response at approximately 22 ms in normal subjects is mediated by a vestibulocollic reflex. The delayed activity in LDs may be a stretch reflex. This is the first demonstration of the latency of the vestibulocollic pathway to natural stimulation in man.
Ito
Y
Y
Department of Oto-Rhino-Laryngology, Gifu University School of Medicine, Japan.
Corna
S
S
von Brevern
M
M
Bronstein
A
A
Rothwell
J
J
Gresty
M
M
D000054:Acceleration; D000328:Adult; D001767:Blinking / Q000502:physiology; D003638:Deafness / Q000503:physiopathology; D004576:Electromyography; D005133:Eye Movements / Q000502:physiology; D005260:Female; D006257:Head / Q000502:physiology*; D006801:Humans; D007759:Labyrinth Diseases / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D009334:Neck Muscles / Q000502:physiology* / Q000503:physiopathology; D012018:Reflex / Q000502:physiology; D014722:Vestibule, Labyrinth / Q000502:physiology