Attentional Modulation of Evoked Potentials and Brain Oscillations are Related to Speech Perception Abilities in Cochlear Implant Users

Background: The sources of variability of outcomes after cochlear implant (CI) surgery are largely unknown but may be related to cognitive factors such as attention and memory.

Objective: The purpose of this study was to use an electrophysiological index of a cognitive process (attention) as a biomarker of speech perception outcome in CI users.

Methods: Adult CI users performed a behavioural categorical consonant-vowel identification task while 64 channels of EEG (electroencephalogram) were recorded. The stimuli were /pa/-/ba/ stimuli that varied in voice onset time (VOT) in 10 ms steps. For each trial, the CI user had to make a decision if they perceived the stimulus as a “pa” or as a “ba”. CI users were “poor performers”, if their speech perception scores fell below 50% and “good performers” if scores were above 50%. On a separate behavioural task, consonant identification was assessed in a 16 consonant “aCa” format (using the Tigerspeech software).

Results: Cortical responses (N1) increased in latency as a function of VOT for the good performing group whereas the poor performing group showed no change N1. The degree of N1 change was related to consonant identification. Time frequency analysis of the EEG revealed alpha desynchronization was greater in the good performing group compared to the poor performing group. Beamformer source analysis showed that the alpha localized to the left auditory cortex the strength was significantly correlated to consonant perception.

Conclusion: Our results indicate that cognitive, attention-related modulation of cortical responses is related to speech perception in CI users.