Temporal Summation In The Acoustic Stapedius Reflex Mechanism

Abstract

Temporal summation in the acoustic stapedius reflex mechanism was studied by monitoring acoustic impedance changes at the ear-drum. The results show that the duration of short acoustic stimuli (“white noise” and 1/1 octave bands of noise) has a pronounced effect on the stapedius reflex response. For a ten-fold increase of stimulus duration the intensity level had to be lowered by about 22 dB in order to elicit the criterion response (50% of maximal obtainable impedance change). For stimulus durations shorter than 5&80 ms, the relationship between sound intensity and stimulus duration was about the same for all types of stimuli, indicating that for such short stimuli temporal summation in the acoustic stapedius reflex is independent of the type of stimulus. For longer durations, several time constants of summation were found. The time constants were largely dependent on the type of stimulus. Possible explanations of these findings are discussed.