Cortical Auditory Evoked Potentials Recorded From Nucleus Hybrid Cochlear Implant Users

Abstract

Objective Nucleus Hybrid CI users hear low-frequency sounds via acoustic stimulation and high frequency sounds via electrical stimulation. This within-subject study compares three different methods of coordinating programming of the acoustic and electrical components of the Hybrid device. Speech perception and cortical auditory evoked potentials (CAEP) were used to assess differences in outcome. The goals of this study were to determine (1) if the evoked potential measures could predict which programming strategy resulted either in better outcome on the speech perception task or was preferred by the listener, and (2) whether CAEPs could be used to predict which subjects benefitted most from having access to the electrical signal provided by the Hybrid implant. Design CAEPs were recorded from 10 Nucleus Hybrid CI users. Study participants were tested using three different experimental MAPs that differed in terms of how much overlap there was between the range of frequencies processed by the acoustic component of the Hybrid device and range of frequencies processed by the electrical component. The study design included allowing participants to acclimatize for a period of up to 4 weeks with each experimental program prior to speech perception and evoked potential testing. Performance using the experimental MAPs was assessed using both a closed-set consonant recognition task and an adaptive test that measured the signal to noise ratio that resulted in 50% correct identification of a set of 12 spondees presented in background noise (SNR-50). Long-duration, synthetic vowels were used to record both the cortical P1-N1-P2 “onset” response and the auditory “change” or ACC response. Correlations between the evoked potential measures and performance on the speech perception tasks are reported. Results Differences in performance using the three programming strategies were not large. Peak-to-peak amplitude of the AAC response was not found to be sensitive enough to accurately predict the programming strategy that resulted in the best performance on either measure of speech perception. All 10 Hybrid CI users had residual low frequency acoustic hearing. For all 10 subjects, allowing them to use both the acoustic and electrical signals provided by the implant improved performance on the consonant recognition task. For most subjects, it also resulted in slightly larger cortical change responses. However, the impact that listening mode had on the cortical change responses was small and again, the correlation between the evoked potential and speech perception results was not significant. Conclusions CAEPs can be successfully measured from Hybrid CI users. The responses that are recorded are similar to those recorded from normal hearing listeners. The goal of this study was to see if CAEPs might play a role either in identifying the experimental program that resulted in best performance on a consonant recognition task or documenting benefit from use of the electrical signal provided by the Hybrid CI. At least for the stimuli...

Electrically Evoked Auditory Event-Related Responses in Patients with Auditory Brainstem Implants: Morphological Characteristics, Test–Retest Reliability, Effects of Stimulation Level, and Association with Auditory Detection

“…Averaged peak-to-peak amplitude of this type of responses ranged from 2.08 to 5.29 μV, which is similar to those measured in pediatric and adult CI users (e.g. Brown et al, 2008, 2015; Firszt et al, 2002; Gordon et al, 2005, 2011; Sharma et al, 2002, 2009). Type 1 responses accounted for 76% of total responses recorded in the present study.…”

“…Averaged maximum peak-to-peak amplitude of this response was 24.28 μV, which is larger than what has been reported for onset eERPs measured in CI users (e.g. Brown et al, 2008, 2015; First et al, 2002; Gordon et al, 2005, 2011; Sharma et al, 2002, 2009). Neural generators for onset eERPs recorded in ABI patients remain unknown.…”

“…Although eERPs have been described in pediatric and adult CI users (e.g. Brown et al, 2008, 2015; First et al, 2002; Gordon et al, 2005, 2011; Sharma et al, 2002, 2009), a direct comparison between responses recorded in ABI and CI patients are difficult due to differences in etiology, electrode design and placement, and potential differences in neural pathways activated by these devices.…”

Effects of Long-Term Musical Training on Cortical Auditory Evoked Potentials

“…This auditory evoked potential can be elicited using long duration, spectrally complex acoustic signals (like speech syllables or musical tones) presented in a passive listening paradigm. It has a fairly large amplitude, and studies have shown that it is possible to measure the P1-N1-P2 response complex in individuals who use conventional hearing aids or a CI to communicate (e.g., Friesen & Tremblay 2006; Tremblay et al 2006a, 2006b; Brown et al 2015). The presence of this CAEP is typically interpreted as evidence that the acoustic signal has been detected.…”

“…It typically is larger in amplitude, has more consistent morphologic features and can be recorded more efficiently than the mismatch negativity. The ACC can be recorded using long duration acoustic stimuli presented in the sound field that are then “processed” either by a hearing aid or a CI (e.g., Martin et al 2008; Billings et al 2012; Martinez et al 2013; Brown et al 2015). There also is evidence in the literature shows that the magnitude of the ACC response is at least roughly correlated with the salience of the “change” used to evoke it (e.g., Martin & Boothroyd 2000; Brown et al 2008; Kim et al 2009).…”