Electrically-evoked frequency following responses (EFFRs) and electrically-evoked auditory brainstem responses (EABRs) in guinea pigs

An important criterion to decide whether a patient is a suitable candidate for a cochlear implant is the functional integrity of the auditory neural pathways. The auditory brainstem responses (ABRs) is currently the most popular AEP for hearing screening in clinical situations. Since the stimulation is acoustic, conventional ABRs testing is not suitable for screening the cochlear implantation. To solve this problem, the measurement of electrically evoked auditory brainstem responses (EABRs) were introduced as a clinical tool for estimating auditory nerve survival. However, it was also reported that even if no EABRs could be recorded, cochlear implantation sometimes provided measurable benefit for people, indicating that EABRs do not fully reflect the residual auditory capability of the severely hearing impaired person. In all previous EABRs studies, the stimuli were electric clicks, which lack periodic features to elicit phase-locking responses. However, the phase-locking response is one of the most significant characteristic of the auditory system and it plays a role in many aspects of auditory perception. Hence, we began studying electrically-evoked frequency following responses (EFFRs), in which the short-term periodical stimuli were firstly used for recording electrically-evoked auditory potentials. In this paper, our works on EFFRs are introduced and overviewed, including 1) the methods and possible problems for recording EFFR in guinea pigs; 2) the comparison between EABRs and EFFRs based on a cochlear impaired model with guinea pigs.