Recovery of the human intra-aural muscle reflex after "pauses" of various depth.

Decay and recovery of the ipsilateral and contralateral stapedius reflex were studied in eight normal hearing subjects. The activity of the intra-aural muscle was recorded as a change of the ear's acoustic impedance in response to prolonged stimulation at 2 000 Hz. A one-second long attenuation of the stimulus tone by 2 to 40 dB was introduced when the response had decayed to a certain level. The recovery following the "pause" was observed. The results show that a "pause" with a depth as small as 2 dB produced approximately 40% of total recovery. A 20 dB attenuation resulted in a recovery equal to that seen after an interruption of the tone. No difference was seen between the ipsilateral and the contralateral reflex. The possibility of using stapedius reflex recovery for diagnosis of otoneurological disorders was discussed.