It was suggested that neural synchrony for electric-evoked potential recordings in CI patients is greater than that for acoustic stimulation in normal-hearing individuals because the auditory nerve is directly stimulated with a rapid-onset electrical pulse. Furthermore, the maximum firing rate and the spread of excitation within the auditory nerve are much larger for electrical stimulation than for normal acoustic stimulation. Accordingly, it has a narrow dynamic range. On the other hand, with electrical stimulation, the operation is mediated through bypassing the IHC activation. The normal activation of auditory nerve fibres involves the excitation of inner hair cells that is why it has a large dynamic range. The dynamic range with electrical stimulation is much less than that induced by acoustic stimulation. Moreover, the phase-locking occurs to the acoustic sine wave to the positive phase of the acoustic stimulation, while it occurs at the peak of the negative phase with the electric stimulation but is more precise to the latter one. The auditory nerve fibers are sharply tuned to the acoustic stimuli than to the electric stimulation. All these processes are bypassed in electrical stimulation of the cochlea in implanted deaf individuals. That in turn will generate receptor potential which leads to the activation of the primary fibers through synapses. In normal ears, acoustic stimulation generates traveling waves that progress from the base of the cochlea toward the apex. General differences between electrical and acoustic stimulationsĮlectrical stimulation of the auditory nerve by cochlear implants induces a pattern of activity that is different from acoustic stimulation in the normal ear. E-ABR has many clinical applications, not only in post-implantation situations but also in preimplantation. A lot of factors affect its waveform, including recording-related factors and stimulus-related and subject-related variables. ConclusionĪfter the increase in the number of cochlear implant receivers, E-ABR provides a promising new tool that can be used to evaluate auditory nerve functions. E-ABR has potential clinical applications in cochlear implants (pre, inter, and postoperative). There are many variables affecting the E-ABR waveform, including recording-related variables, stimulus-related variables, and subject-related variables. E-ABR is characterized by larger amplitudes and shorter latencies than the acoustic, and it has a steeper latency-intensity function. There are differences between both acoustic auditory brainstem response (A-ABR) and E-ABR. The largest is corresponding to wave V of the acoustic one. Body of abstractĮ-ABR is characterized by three positive peaks (eII, eIII, and eV) generated from the auditory nerve, cochlear nucleus, and perhaps from neurons in the lateral lemniscus or inferior colliculus. It plays a vital role, especially after the increased number of cochlear implant receivers. It is considered a short latency evoked potential. Electrically evoked auditory brainstem response (E-ABR) is an evoked potential recorded from the auditory nerve in response to electric stimulation.
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