Measuring hearing instrument sound modification using integrated ear-EEG
Keywords:ear-EEG, Hearing Aid, AEP
We integrated ear electrodes into a live hearing system and evaluated the feasibility of recording electroencephalography (EEG) features with this setup using an auditory discrimination experiment. The long-term goal is to construct a closed-loop brain-computer-interface that is integrated in a mobile research hearing system. Here, the EEG setup consists of 3 electrodes embedded in the earmoulds of an experimental hearing system and 10 flex-printed electrodes positioned around each ear, all connected to a wireless EEG amplifier. Four consecutive identical broadband stimuli were played in headphones while the spectral profile of sounds arriving at the eardrum was altered by switching the signal processing setting of the hearing system. Such switches were made between presentation of the third and the fourth stimulus, in half of all epochs. Seventeen normal hearing subjects participated and were instructed to indicate whether the last stimulus sounded different. The behavioural data verified clear audibility of the switches. The EEG analysis revealed differences between switch and no-switch trials in the N1 and P3 latency range. Importantly, changes in the spectral content of the noise floor of the hearing device were already sufficient to elicit these responses. These results confirm that stimulus-related brain signals acquired from ear-EEG during real-time audio processing can be successfully derived.
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