Characteristics of cochlear microphonic (CM) of guinea pigs, when compensated for electrical capacitive shunting within the cochlea, parallel corresponding mechanical characteristics. Specifically, good agreement is found for the middle-ear transfer characteristic, basilar-membrane phase, and cochlear travel times. CM corrections derived from guinea-pig experiments have been extrapolated to CM recorded in Mongolian gerbils to obtain estimates of middle-ear and basilar-membrane characteristics, a cochlear frequency map, and cochlear travel times for both animals. The estimates indicate that basilar-membrane tuning curves are almost symmetrical in the apical turn. Model experiments suggest that the apparent sharpening of the low-frequency leg of these curves is produced by a shunting effect of the helicotrema. Comparisons are also made among results obtained with three different electrode configurations: a single electrode in scala media (SM), a differential pair in scalae media and tympani (SM–ST), and a differential pair in scalae vestibuli and tympani (SV–ST). Results from both guinea pigs and gerbils indicate a slight advantage in the SM–ST configuration.
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Schmiedt et al. (1977) studied this question.