On the relationship between auditory cognition and speech intelligibility in cochlear implant users: An ERP study

Abstract

There is a high degree of variability in speech intelligibility outcomes across cochlear-implant (CI) users. To better understand how auditory cognition affects speech intelligibility with the CI, we performed an electroencephalography study in which we examined the relationship between central auditory processing, cognitive abilities, and speech intelligibility. Postlingually deafened CI users (N=13) and matched normal-hearing (NH) listeners (N=13) performed an oddball task with words presented in different background conditions (quiet, stationary noise, modulated noise). Participants had to categorize words as living (targets) or non-living entities (standards). We also assessed participants' working memory (WM) capacity and verbal abilities. For the oddball task, we found lower hit rates and prolonged response times in CI users when compared with NH listeners. Noise-related prolongation of the N1 amplitude was found for all participants. Further, we observed group-specific modulation effects of event-related potentials (ERPs) as a function of background noise. While NH listeners showed stronger noise-related modulation of the N1 latency, CI users revealed enhanced modulation effects of the N2/N4 latency. In general, higher-order processing (N2/N4, P3) was prolonged in CI users in all background conditions when compared with NH listeners. Longer N2/N4 latency in CI users suggests that these individuals have difficulties to map acoustic-phonetic features to lexical representations. These difficulties seem to be increased for speech-in-noise conditions when compared with speech in quiet background. Correlation analyses showed that shorter ERP latencies were related to enhanced speech intelligibility (N1, N2/N4), better lexical fluency (N1), and lower ratings of listening effort (N2/N4) in CI users. In sum, our findings suggest that CI users and NH listeners differ with regards to both the sensory and the higher-order processing of speech in quiet as well as in noisy background conditions. Our results also revealed that verbal abilities are related to speech processing and speech intelligibility in CI users, confirming the view that auditory cognition plays an important role for CI outcome. We conclude that differences in auditory-cognitive processing contribute to the variability in speech performance outcomes observed in CI users. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Hannover, Finke.Mareike@mh-hannover.de AbstractThere is a high degree of variability in speech intelligibility outcomes across cochlear-implant (CI) users. To better understand how auditory cognition aff...

Consequences of Stimulus Type on Higher-Order Processing in Single-Sided Deaf Cochlear Implant Users

“…According to this model, one would hypothesize that verbal abilities relate to late event-related potential (ERP) components as well as to the speech intelligibility outcome with the CI . This idea has been supported by our previous study which revealed that the N2/N4 latency of CI users was related to speech perception scores as well as to the subjective listening effort ratings in these individuals [Finke et al, 2016]. However, the previous results have been obtained with bilaterally and bimodally fitted CI users.…”

“…Participants were tested with an auditory oddball paradigm with a target probability of 20% [Finke et al, 2016;Polich, 2007]. Each trial consisted of a disyllabic German noun (800 ms long), and participants had to identify it as a living or nonliving entity ( Fig.…”

“…Some studies could clearly distinguish the components from each other [Deacon et al, 1991;van den Brink et al, 2001] while other studies suggest that it is likely that the N2 is not distinct from the N4 [Brink and Hagoort, 2004;Polich, 1985]. With regard to CI users, lexical information access (reflected by N2/N4 latency) and word classification (reflected by P3 latency) were found to be delayed when compared to NH listeners [Beynon et al, 2005;Finke et al, 2016;Henkin et al, 2009Henkin et al, , 2014. Thus, speech perception in adverse listening conditions seems to be influ-enced by higher-order processes as well as by verbal WM capacity and lexical abilities, and may be affected by phonological processing as well [Akeroyd, 2008;Andersson, 2002;Banks et al, 2015;Benard et al, 2014;Lunner, 2003;Lyxell et al, 1998;Rönnberg et al, 2013;Rudner et al, 2008;Zekveld et al, 2007a, b].…”

“…Recent studies have suggested that the CI outcome is related to higher-order resources such as verbal abilities or working memory (WM) capacity [Finke et al, 2015[Finke et al, , 2016Kral et al, 2016;Rönnberg et al, 2013]. According to the Ease of Language Understanding model by Rönn-berg et al [2013], WM capacity is needed to support speech understanding via an explicit processing loop in adverse listening conditions, such as listening via a CI.…”

“…Similar to previous studies, the neuronal processes underlying speech perception were examined in CI users with an oddball paradigm [Beynon et al, 2005;Finke et al, 2015Finke et al, , 2016Groenen et al, 2009;Henkin et al, 2009]. In a series of standard syllables or words, infrequent deviant stimuli were intermixed, and participants were asked to respond to these infrequent targets [Polich, 2007].…”