Pushkar Deshpande1,2, Christian Brandt1,2, Stefan Debener3, Tobias Neher1,2
1Institute of Clinical Research, University of Southern Denmark, Odense, Denmark
2Research Unit for ORL – Head & Neck Surgery and Audiology, Odense University Hospital, Odense, Denmark; University of Southern Denmark, Odense, Denmark
3Department of Psychology, University of Oldenburg, Oldenburg, Germany
Effective communication requires good speech perception abilities. Speech perception can be assessed with behavioral and electrophysiological methods. Relating these two types of measurements to each other can provide insights into the underlying cortical processes. The current study aimed to develop a digit-based test battery suited for eliciting different speech-evoked cortical responses and to relate the speech-evoked cortical responses to behavioral measures of speech detection, discrimination, and comprehension. Thirty young normal-hearing native Danish speakers with normal or corrected-to-normal vision participated. The digit-triplet lists from the Dantale-I speech corpus were used as stimulus material. All measurements were carried out in the presence of stationary speech-shaped noise at 67 dB(C) SPL. The behavioral measurements included speech detection thresholds (SDTs), speech recognition thresholds (SRTs), and speech comprehension scores (SCSs). For the electrophysiological measurements, multi-channel electroencephalography (EEG) recordings were performed. N100 and P300 responses were evoked using an active auditory oddball paradigm. N400 and Late Positive Complex (LPC) responses were evoked using congruent and incongruent digit sequences that were presented using audio-only or audio-visual paradigms. All EEG components could be evoked successfully. While no correlations between the SDTs and N100 responses were found, the SRTs were correlated with P300 responses (r = -0.45, p < 0.05) and the SCSs were correlated with the EEG responses to the congruent and incongruent digit sequences. Regarding the N400 and LPC responses, there were significant amplitude differences between the audio-only and audio-visual paradigms. Overall, the developed test battery was found to be usable and to produce reliable data. Follow-up studies with hearing-impaired individuals will provide further insights into the consequences of hearing loss on cortical speech processing. The audio-only and audio-visual paradigms will allow investigating similarities and differences between unimodal and bimodal speech perception.