Neurophysiology of Cochlear Implant Users II: Comparison Among Speech Perception, Dynamic Range, and Physiological Measures

Abstract

Objective: As the need for objective measures with cochlear implant users increases, it is critical to understand how electrical potentials behave when stimulus parameters are systematically varied. The purpose of this study was to record and evaluate the effects of implanted electrode site and stimulus current level on latency, amplitude, and threshold measures of electrically evoked auditory potentials, representing brainstem and cortical levels of the auditory system. Design:The electrical auditory brainstem response (EABR), electrical auditory middle latency response (EAMLR), and the electrical late auditory response (ELAR) were recorded from the same experimental subjects, 11 adult Clarion cochlear implant users. The Waves II, III, and V of the EABR, the Na-Pa complex of the EAMLR and the N1-P2 complex of the ELAR were investigated relative to electrode site (along the intra-cochlear electrode array) and stimulus current level. Evoked potential measures were examined for statistical significance using analysis of variance (ANOVA) for repeated measures.Results: For the EABR, Wave V latency was significantly longer for the basal electrode (7) compared with the mid (4) and apical (1) electrodes. For the EAMLR and ELAR, there were no significant differences in latency by electrode site. For all subjects and each of the evoked potentials, the apical electrodes tended to have the largest amplitude and the basal electrodes the smallest amplitude, although amplitude differences did not reach statistical significance. In general, decreases in stimulus current level resulted in statistically significant decreases in the amplitude of Wave V, Na-Pa and N1-P2. The evoked potential thresholds for Wave V, Na-Pa, and N1-P2 were significantly higher for the basal Electrode 7 than for Electrodes 4 and 1. Conclusions: Electrophysiologic responses of Waves

Cochlear implant artifact attenuation in late auditory evoked potentials: A single channel approach

“…The second factor hindering the use of cortical evoked potentials in clinical use is that a stimulation paradigm or neural response that shows a strong correlation with speech perception in a large population of CI users has yet to be found. Firszt et al (2002) showed, for a small population of CI users, a significant correlation between speech perception in quiet and a measure of mid-latency NaePa amplitude normalized for different stimulation levels. Zhang et al (2011) found that a mismatch negativity measure could discriminate between good and bad performers on a speech perception task.…”

“…A number of studies have indicated that cortical evoked potentials may be useful for predicting speech perception outcomes for CI subjects (Wable et al, 2000;Firszt et al, 2002;Kelly et al, 2005;Zhang et al, 2011), more so than earlier evoked potential responses such as auditory nerve electric compound action potentials (ECAPs) or auditory brainstem responses (Miller et al, 2008). However, two factors appear to have limited the clinical application of cortical evoked potentials for CI subjects.…”

“…However, the development of such neural metrics has been hampered by the large CI related electrical artifact, which contaminates evoked potential recordings in these subjects. Firszt et al (2002) found that cortical evoked potentials may be useful for predicting speech perception outcomes for CI. However, to minimize the artifact, this study used very short simple stimuli which are unable to fully probe the complex processing that takes place in the auditory system.…”

Psychophysical Versus Physiological Spatial Forward Masking and the Relation to Speech Perception in Cochlear Implants

“…CI users with greater temporal integration have been shown to have better speech-perception performance (Chatterjee, 1999;Firszt, Chambers, & Kraus, 2002). Subjects with greater temporal integration will be more likely to have large differences in current level between psychophysical and physiological measures due to the different stimuli used.…”

Relationship between Intraoperative eCAP Thresholds and Postoperative Psychoacoustic Levels as a Prognostic Tool in Evaluating the Rehabilitation of Cochlear Implantees

“…electrically evoked stapedius reflex thresholds, electrically evoked neuronal responses). The latter technique became widely accepted over the last few years [Firszt et al, 2002;Kelly et al, 2005]. The most frequently recorded neural response in CI fitting is the electrically evoked compound action potential of the auditory nerve (eCAP).…”