Influence of an acoustic preparatory signal on postural reflexes of the distal leg muscles in humans.
In standing subjects the sudden displacement of a platform toe-up evokes a stabilizing postural response of the anterior tibial muscle (long-latency reflex). A preparatory signal (acoustic warning stimulus) preceding the postural perturbation by 1 s results in a significant decrease in latency of this long-latency response. There is no parallel modulation of the afferent cortical input in terms of evoked cerebral potentials following platform tilts toe-up nor of efferent cortico-spinal functions as evaluated by means of transcranial magnetic stimulation. Conceivable underlying mechanisms include faster intraspinal and/or intracortical processing of afferent input or switching to a shorter spinal reflex pathway.
Ackermann
H
H
Department of Neurology, University of Tübingen, F.R.G.
Dichgans
J
J
Guschlbauer
B
B
D000161:Acoustic Stimulation; D000328:Adult; D002540:Cerebral Cortex / Q000502:physiology; D005071:Evoked Potentials; D005260:Female; D006801:Humans; D007866:Leg; D008297:Male; D009132:Muscles / Q000502:physiology*; D011187:Posture / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology; D012018:Reflex / Q000502:physiology*; D013997:Time Factors