Age effects on cognitive functions and speech-in-noise processing: An event-related potential study with cochlear-implant users and normal-hearing listeners

Abstract

A cochlear implant (CI) can partially restore hearing in individuals with profound sensorineural hearing loss. However, electrical hearing with a CI is limited and highly variable. The current study aimed to better understand the different factors contributing to this variability by examining how age affects cognitive functions and cortical speech processing in CI users. Electroencephalography (EEG) was applied while two groups of CI users (young and elderly; N = 13 each) and normal-hearing (NH) listeners (young and elderly; N = 13 each) performed an auditory sentence categorization task, including semantically correct and incorrect sentences presented either with or without background noise. Event-related potentials (ERPs) representing earlier, sensory-driven processes (N1-P2 complex to sentence onset) and later, cognitive-linguistic integration processes (N400 to semantically correct/incorrect sentence-final words) were compared between the different groups and speech conditions. The results revealed reduced amplitudes and prolonged latencies of auditory ERPs in CI users compared to NH listeners, both at earlier (N1, P2) and later processing stages (N400 effect). In addition to this hearing-group effect, CI users and NH listeners showed a comparable background-noise effect, as indicated by reduced hit rates and reduced (P2) and delayed (N1/P2) ERPs in conditions with background noise. Moreover, we observed an age effect in CI users and NH listeners, with young individuals showing improved specific cognitive functions (working memory capacity, cognitive flexibility and verbal learning/retrieval), reduced latencies (N1/P2), decreased N1 amplitudes and an increased N400 effect when compared to the elderly. In sum, our findings extend previous research by showing that the CI users’ speech processing is impaired not only at earlier (sensory) but also at later (semantic integration) processing stages, both in conditions with and without background noise. Using objective ERP measures, our study provides further evidence of strong age effects on cortical speech processing, which can be observed in both the NH listeners and the CI users. We conclude that elderly individuals require more effortful processing at sensory stages of speech processing, which however seems to be at the cost of the limited resources available for the later semantic integration processes.

Multisensory integration augmenting motor processes among older adults

“…The less negative-going r-LRP amplitude revealed in older participants in the audiovisual condition reflects stronger activations in the motor cortices ( Sterr and Dean, 2008 ). The frontal P2 is within the aging-related cognitive reserve framework ( Burkhardt et al, 2022 ), which can be deployed by the premotor cortex ( Stern et al, 2005 ; Quinzi et al, 2020 ). A less negative-going r-LRP was previously reported to associate with lower difficult level motor tasks ( Nagy et al, 2020 ).…”

Die N400-Komponente im EEG als Marker für Spracherwerb und Wortverarbeitung nach CI-Versorgung

“…[20]). Dieser Effekt trat in anderen CI-Satzverarbeitungsstudien nicht auf [15,21]. Jedoch waren die sprachlichen Leistungen der CI-Träger in den anderen Studien besser als in der hier diskutierten Gruppe von Kessler…”

“…et al Weitere Studien sind daher notwendig, um zu überprüfen, ob der biphasische Effekt ein typisches Potenzialmuster für CI-Träger mit eher schlechtem Sprachverstehen darstellt.Burkhardt et al[21] untersuchten ebenfalls die Verarbeitung von Sätzen mittels EEG bei CI-Trägern. Es wurde das Material aus Kessler et al[19] verwendet, bei dem semantisch korrekte mit semantisch inkorrekten Sätzen verglichen wurden.Burkhardt et al variierten jedoch systematisch das Alter der CI-Träger sowie einer gematchten normalhörenden Gruppe (NH) (jüngere Gruppe: CI: mittleres Alter 25,5 Jahre, ältere Gruppe: CI: mittleres Alter: 71,1 Jahre).…”

“…Zudem war auch die Amplitude des Effekts signifikant reduziert. Es zeigt sich also auch hier ein deutlicher Verarbeitungsunterschied bezüglich semantischer Integrationsprozesse zwischen Normalhörenden und CI-Trägern Burkhardt et al (2022). fanden zudem einen Einfluss des Alters auf den N400-Effekt, der für die CI-Gruppe und die Kontrollgruppe gleichermaßen galt: Der N400-Effekt war für ältere Probanden geringer ausgeprägt als für jüngere Probanden.…”