Electrocochleography

[2] The most common clinical applications of electrocochleography include: The basilar membrane and the hair cells of the cochlea function as a sharply tuned frequency analyzer.

Movement of the stapes on the oval window generates a pressure wave in the perilymph within the cochlea, causing the basilar membrane to vibrate.

The flow of ions generates an AC current through the hair cell surface, at the same frequency as the acoustic stimulus.

The hair cells function as a transducer, converting the mechanical movement of the basilar membrane into electrical voltage, in a process requiring ATP from the stria vascularis as an energy source.

The depolarized hair cell releases neurotransmitters across a synapse to primary auditory neurons of the spiral ganglion.

The neurophonic represents the neural part (auditory nerve spikes) phased-locked to the stimulus and is similar to the Frequency following response.

Although historically it has been the least studied, renewed interest has surfaced due to changes in the SP reported in cases of endolymphatic hydrops or Ménière's disease.

As a result, researchers often use the sum (or difference) of responses to stimuli of alternating polarity to dissociate the CAP from CM.

Derbyshire from Harvard replicated the study and concluded that the waves were in fact cochlear origin and not from the auditory nerve.

[9] Fromm et al. were the first investigators to employ the ECochG technique in humans by inserting a wire electrode through the tympanic membrane and recording the CM from the niche of the round window and cochlear promontory.

Fisch and Ruben were the first to record the compound action potentials from both the round window and the eighth cranial nerve (CN VIII) in cats and mice.

In 1971, Moore conducted five experiments in which he recorded CM and AP from 38 human subjects using surface electrodes.