title: Asymmetries in the acoustic reflexes of the cat stapedius muscle.
abstract: Electromyographic activity (EMG) was used to monitor contractions of the stapedius muscle evoked by both ipsilateral and contralateral sound in ketamine-anesthetized or decerebrate cats. After the onset of a continuing tone, stapedius EMG often had bursts of activity at regular intervals; similar bursts were also observed in the EMG from the tensor tympani muscle. Plots of the r.m.s. amplitude of stapedius-EMG versus sound level usually had a steep rising phase (small dynamic range) and a plateau at high sound levels. For sound stimulation at 1 kHz, the crossed stapedius reflex had a lower maximum amplitude (ave. amplitude ratio: 0.37) and a higher threshold (ave. 8 dB) than the uncrossed reflex. Since the uncrossed reflex evokes considerably more stapedius EMG than does the crossed reflex, it probably produces correspondingly greater changes in middle-ear sound transmission.
mesh_terms: D000161:Acoustic Stimulation; D000818:Animals; D001309:Auditory Threshold / Q000502:physiology; D002415:Cats; D004576:Electromyography; D007839:Functional Laterality / Q000502:physiology; D009132:Muscles / Q000502:physiology*; D012016:Reference Values; D012022:Reflex, Acoustic; D013016:Sound; D013198:Stapedius / Q000502:physiology*