A look at neural integration in the human auditory system through the stapedius muscle reflex.

Ipsilateral and contralateral stapedius muscle contractions were studied as functions of the sound pressure level (SPL) and duration of 2-kHz tone bursts. The study complemented a preceding study in which temporal summation of stapedius muscle contractions produced by pairs of short tone bursts was determined and analyzed. The muscle contractions were determined indirectly by measuring changes in the acoustic impedance they produced at the tympanic membrane.

Auditory system: Peripheral nonlinearity and central additivity, as revealed in the human stapedius-muscle reflex.

Human stapedius-muscle contractions in response to 3-kHz, 20-msec tone bursts were determined indirectly by measuring the associated acoustic-impedance changes at the tympanic membrane with an acoustic bridge. The measurement was possible because the bridge practically eliminates the effect of the ear-canal air volume interposed between the tympanic membrane and the tip of the measuring tube. By using burst pairs, temporal additivity of the muscle responses was demonstrated both when the stimulus bursts were presented contralaterally to the measured impedance changes and when the first burst was presented ipsilaterally.

On a psychophysical transformed-rule up and down method converging on a 75% level of correct responses.

Transformed-rule up and down psychophysical methods have gained great popularity, mainly because they combine criterion-free responses with an adaptive procedure allowing rapid determination of an average stimulus threshold at various criterion levels of correct responses. The statistical theory underlying the methods now in routine use is based on sets of consecutive responses with assumed constant probabilities of occurrence. The response rules requiring consecutive responses prevent the possibility of using the most desirable response criterion, that of 75% correct responses.

Place code for pitch: a necessary revision.

It is widely believed that the location of the cochlear excitation maximum, which has been shown by Békésy to depend on sound frequency and move from the cochlear apex to its base as the frequency increases, is a code for subjective pitch. The pitch of a tone is known to be practically independent of sound intensity. If the location does determine the pitch, it too must remain invariant.

Cochlear mechanisms of frequency and intensity coding. II. Dynamic range and the code for loudness.

Our preceding paper described SPL-dependent changes in the shape of transfer functions recorded from inner and outer hair cells as well as supporting cells, in the 500-2500 Hz regions of the Mongolian gerbil cochlea. As SPL was increased, large shifts were observed in the peak of the transfer function. A strongly compressive nonlinearity was also observed at CF.