Stapedius reflex: On some fundamental temporal characteristics

Abstract

Effects of neural temporal summation and adaptation on the stapedius reflex are examined with the help of monotic and dichotic pairs of tone bursts. The tone intensities were so chosen that each burst presented separately evoked a constant response. The results show that the apparent summation of the effects of dichotic bursts is greater than that of monotic bursts and decays monotonically as the interburst time interval increases. With monotic bursts the apparent summation effect has a flat maximum around a time interval between the burst onsets of about 60 ms. The dichotic as well as the monotic reflex arc contains at least one nonlinearity since the summated effect of the bursts exceeds the arithmetic sum. The measured characteristics can be accounted for quantitatively by a model containing a peripheral linear adaptation stage with a recovery time constant on the order of 50 ms, a linear central temporal integrator with a time constant of about 200 ms and a threshold, all connected in series. All the numerical constants are consistent with those found in neurophysiological and psychophysical experiments. The inference that the threshold follows the integrator may prove to be of major interest.