Effects of auditory pathway anatomy and deafness characteristics? (1): On electrically evoked auditory brainstem responses

Recording of electrically evoked auditory brainstem responses after electrical stimulation with biphasic, triphasic and precision triphasic pulses

“…A time shift of approximately 1 ms is caused by bypassing outer and middle ear and directly stimulating the auditory nerve (e.g., Guiraud et al, 2007). E-ABR Jewett waves are called eIII and eV (e.g., Guiraud et al, 2007) to distinguish them from acoustic waves.…”

Effects of auditory pathway anatomy and deafness characteristics? Part 2: On electrically evoked late auditory responses

“…Thus, ELAR latency was longer for poorer audiograms and longer durations of deafness and this relationship appeared to be independent of stimulation parameters such as stimulation site. Comparison between these findings and those from the equivalent study on EABR waves IIIe and Ve latency [Guiraud, J., Gallego, S., Arnold, L., Boyle, P., Truy, E., Collet, L., 2007. Effects of auditory pathway anatomy and deafness characteristics?…”

“…When the auxiliary input of the sound processor and then the recipient's program are used, this latency decrease may be compensated by the time the cochlear implant takes to process the sound, resulting in latencies similar to those of normal-hearing subjects. Nevertheless, the latency of the electrically evoked potential may be linked with the degeneration of auditory fibers (Guiraud et al, 2007) and reflect the maturity of the auditory pathway (Ponton et al, 1996a(Ponton et al, ,b, 1999(Ponton et al, , 2000Ponton and Don, 1995;Ponton and Eggermont, 2001;Eggermont et al, 1997;Sharma et al, 2002Sharma et al, , 2005. Hence, it seems appropriate to use ELAR latency to investigate the impact of deafness on the auditory pathway if they are recorded in the same way for all subjects.…”

“…The relationship between ELAR latency and deafness characteristics would then be disrupted by a tonotopic gradient of ELAR latency according to the stimulation site. On the one hand, the peripheral tonotopic gradient found with electrical auditory brainstem responses (EABRs) (Allum et al, 1990;Shallop et al, 1990;Abbas and Brown, 1991;Miller et al, 1993;Firszt et al, 2002a;Guiraud et al, 2007) could indeed be projected at upper levels of the auditory pathway. ELAR latency would then be longer for activation of basal electrodes and reflect anatomic aspects of the auditory pathway periphery since auditory fibers are longer (Moore, 1987;Spoendlin and Schrott, 1989) and more numerous (Hinojosa et al, 1985;Spoendlin and Schrott, 1990) at the cochlea base.…”

“…In the present study, the effects of the cochlear site of stimulation and deafness characteristics on the ELAR latency were investigated using the same protocol as in a previous study involving EABR latency (Guiraud et al, 2007). On the one hand, the effects of auditory pathway anatomy on ELAR latency (i.e., whether the neural conduction speed varies according to the part of the auditory pathway responsible for a specific pitch) were studied by comparing latencies recorded for stimulation at various sites on the electrode array.…”