Summating Potentials of the Cochlea

Abstract

When the ear is stimulated by a steady tone scala media and scala vestibuli become less positive electrically relative to scala tympani. This ‘summating potential’ (SP) is a d.c. change related to the root-mean-square of the acoustic pressure, integrated over one or two waves. It increases up to injurious sound pressure levels. It is increased by additional positive polarization of scala vestibuli or media. It is modified and may even be reversed in sign by hydrostatic displacement of the cochlear partition. It broadly resembles the cochlear microphonic (CM) but is more resistant to most drugs and anoxia. The negative SP depends on the integrity of the internal hair cells. The external hair cells produce CM and may also generate small SPs, usually positive in sign. The SP generated by 7000 cps tone bursts is strong in the basal turn while those by 2000 and 500 cps are very small here but are strong in the second and third turns, respectively. The theory is proposed that the negative SP is the response of the internal hair cells, an amplifier action intermediate between a mechanical detector action of the cochlear partition and the excitation of nerve impulses. Both CM and SP depend on bending of the ‘hairs’ of the sensory cells in the proper direction.

Electrical Potentials of the Subtectorial Space in the Guinea Pig Cochlea

“…against the CM of the scala tympani.In other words,the phase of the subtectorial CM was the same as that recorded from the scala media.It has been known that the summating potential(SP)has a negative polarity at high frequencies when recorded in the scala media of the basal turn (DAVIS et al,1958). SP's were positive in polarity through the hair cell layer of the organ of Corti and negative in the subtectorial space.The Alcian Blue marking verified that the polarity change occurred at the interface between the hair cell layer and the subtectorial space.…”

Using the Cochlear Microphonic as a Tool to Evaluate Cochlear Function in Mouse Models of Hearing

“…However, there is value in recording the CM near its source to maximize signal-to-noise ratio, i.e., the remote recording of CM still presents technical challenges and difficulties with interpretation. The prevailing notion is that mechanical stimulation of cochlear hair cells results in the modulation of their transducer currents (Davis et al 1958;Hudspeth and Corey 1977). Since the cells are embedded in the electrical network of the organ of Corti and surrounding fluid spaces, alterations of transducer currents produce changes in extracellular current flow.…”

Influence of Direct-Current Polarization of the Cochlear Partition on the Summating Potentials

“…Comparable evidence, to some extent, has been provided by the studies of Davis et al (1958aDavis et al ( , 1958b, Konishi and Yasuno (1963), and Honrubia and Ward (1969a). The CM elicited by pure tones provides a useful basis of comparison.…”

“…We have also used this method to study the nonlinearities underlying harmonic distortion in microphonics (Durrant and Dallos, 1972). In the past, dc polarization has proven useful in the study of differences between the cochlear potentials as well as their interdependence (Tasaki and Ferngndez, 1952; Davis et al, 1958aDavis et al, , 1958bKonishi and Yasuno, 1963;Honrubia and Ward, 1969a;Teas et al, 1970). By essentially altering the electrical operating point of the system, t differences in the production of the various cochlear potentials have been observed.…”