Table 1.
Common cochlear and vestibular electrophysiological activity used to objectively measure inner ear function.
| Response | Stimulus | Latency (ms) | Source | Origin |
|---|---|---|---|---|
| Unitary potential | Spont. | N/A | Neuron(s) | The spontaneous field potential of a single neuron, or collection of neurons, measured distant to the cell. Requires special recording techniques to extract it from noise. |
| Neural noise or neurophonic | Spont. or ACS | N/A | Nerve | The ensemble electrical activity related to stochastic or cyclic activity of the 8th nerve. |
| Compound action potential (CAP) | ACS | ~1 | Nerve | The compound summation of synchronously occurring unitary potentials. |
| Cochlear microphonic (CM) | ACS | <0.1 | Hair cells | The field potential generated by hair cells. Typically recorded from the cochlear fluids. |
| Summating potential (SP) | ACS | <0.1 | Hair cells | The charge imbalance (i.e., asymmetry) of the hair cell field potential, which is obtained by removing the symmetric components of the CM (either by stimulus inversion and averaging, or low-pass filtering). |
| Auditory brainstem response (ABR) | ACS | 1–7 | Nerve/ Brainstem | The compound summation of synchronously occurring neural activity in the auditory brainstem. |
| eCAP | Current | 0–0.5 | Nerve | An electrically evoked CAP |
| Middle and long latency response | ACS | 10–500 | Cortex | The compound summation of synchronously occurring neural activity in the auditory cortex. |
| Post-auricular muscle response | ACS | 12–20 | Myocytes | A compound summation of the electrical response of the post-auricular muscle. |
| Frequency following response | ACS | N/A | Nerve/ Brainstem | The ensemble electrical activity related to cyclic activity of the auditory brainstem. |
| Vestibular short latency evoked potential (VsEP) | BCV | 0.5 | Nerve/ Brainstem | The compound summation of synchronously occurring neural activity of the vestibular nerve and brainstem. |
| Vestibular microphonic (VM) | BCV | <0.1 | Hair cell | The field potential generated by hair cells. Typically recorded from the vestibule fluids. |
| Vestibular evoked myogenic potential (VEMP) | BCV | 10–20 | Myocytes | A compound summation of the electrical activity of the extra-ocular or sternocleidomastoid muscles. |
Also provided is the typical stimulus for each response (Spont., Spontaneous; ACS, Air Conducted Sound; BCV, Bone Conducted Vibration, N/A, not applicable), and a brief explanation of the origin of each activity. Highlighted responses refer to those typically forming parts of ECochG and EVestG responses. The latency refers to the time after the onset of the stimulus, where the stimulus is evoked by the onset of a stimulus.