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

Abstract

The effects of electrically biasing the cochlear partition on the summating potentials were investigated in guinea pigs. The DIF (DIF=SV--ST) and AVE (2 AVE=SV+ST) SP responses were observed under polarization as well as the cochlear microphonics. These responses were recorded and the cochlear partition was polarized in the first and third turns; a wide range of stimulus parameters was utilized. The negative DIF and positive AVE components exhibited similar qualitative effects of electrical biasing as the (pure tone) CM, but the amount of change induced in the former zesponses was typically three or more times greater than that seen in the CM. While the DIF + exhibited the opposite effects of polarization, compared to these responses, the results revealed an underlying relationship between the positive and negative DIF responses. As a rule, positive polarization currents caused the DIF responses to become less positive and more negative while the opposite was true for negative currents. No systematic level-dependent effects of electrical biasing were observed in the behavior of the negative DIF or positive AVE or in the positive DIF, given the complexities of its input-output function (without polarization). The results pertaining to the negative AVE component provided little basis for concrete conclusions concerning the effects of polarization on this component. The findings of this investigation reflect the involvement of electromechanical nonlinearities in the generation of the summating potentials.

Electrocochleography: A Review of Recording Approaches, Clinical Applications, and New Findings in Adults and Children

“…One rationale that has been offered (but not verified) for this finding is that an increase in endolymph volume creates mechanical biasing of vibration of the organ of Corti that amplifies the SP since at least some of its components represent nonlinearities in the transduction process. Whether the nature of this increased distortion is mechanical (Gibson et al, 1977) and/or electrical (Durrant and Dallos, 1972;Durrant and Gans, 1975) has not been resolved, and other factors such as biochemical and/or vascular changes may also be responsible (Eggermont, 1976;Goin et al, 1982;Staller, 1986). Despite verification of its bases, an enlarged SP/AP amplitude ratio has evolved as the primary characteristic of an electrocochleogram that is positive for MD.…”

Electrocochleography in the Evaluation of Patients with Ménière's Disease/Endolymphatic Hydrops

“…However, SP-like potentials have since been observed inside hair cells, and it is now clear and that the SP is not an epiphenomenon (e.g., Dallos, 1973). It also has long been known that the SP is also sensitive to mechanical and electrical biasing (Durrant and Dallos, 1972;Durrant and Gans, 1977). The nonlinear nature of the SP has made it useful for monitoring certain clinical conditions such as MD/ELH, which may augment nonlinearities in the transduction process.…”

ECoG Results in Perilymphatic Fistula: Clinical and Experimental Studies

“…Methods (Patients). Between 1980 and 1986, twenty-seven (27) patients operated on for suspected PLF had surgically confirmed PLF. Only patients with preoperative ECoG and no history of other otologic surgery were included in this study.…”