Utility of Electrically Evoked Potentials in Cochlear Implant Users / 대한이비인후과학회지

Cochlear implants (CIs) are generally used in individuals with severe to profound hearing loss. Needs for objective measures with CI users have increased due to implantation of children at younger ages and large variation in performance. To date, a significant body of research has been published that describes the general methodology used to measure electrically evoked neural responses as well as issues and stimulation paradigms relevant to the measurement of specific neural responses and several potential applications for objective measures with CI users. Objective measures of cochlear implant function have most certainly played a role in developing a better understanding of the process of electrical stimulation of the auditory nerve and the activation of the central auditory pathways. An important remaining issue in further improvements with cochlear implants is the better understanding of variability across subjects and the development of methods to improve signal processing in poor performers. The measurement of electrically evoked neural activity, both peripheral and central response, can be an important tool for accomplishing such tasks.

Cortical Responses Evoked by the Light and Electricity in the Rabbit Retina

PURPOSE: By recording the electrically evoked potential (EEP) we tried to verify that focal electrical stimulation of retina sends a signal to the cortex that is similar to that elicited by light and also to investigate optimal stimulus parameters. METHODS: Five New Zealand white rabbits were placed under anesthesia. A tungsten bipolar stimulating electrode (diameter: 250 um) was placed on the vitreal surface of the retina. Cutaneous Ag/AgCl patch electrodes of VEP were used to record EEP. EEP was recorded at each stimulation. Focal visual evoked potentials (VEPs) were also recorded and compared to the focal EEP to ascertain cortical origin of the EEP, and similarities of the EEP to the VEP were determined. RESULTS: EEP recordings were elicited in 8 eyes. Current amplitudes which produced detectable responses ranged from 100 to 5000 micro A. In our best series, EEP amplitudes increased by 8 to 119 micro V in response to the current increasing from 100 to 1000 micro A. In comparing latencies of the EEP and focal VEP, the EEP latencies were 12~16 ms faster, which supports our EEP recording was done properly. CONCLUSIONS: EEPs obtained using VEP setting with adequate parameters of current duration and threshold level for the retinal implant showed that use of the EEP response is a good way to monitor the proper functioning of the retinal implant.