ERP assessment of word processing under broadcast bit rate limitations
Anne K Porbadnigk, Jan-Niklas Antons, Matthias S Treder, Benjamin Blankertz, Robert Schleicher, Sebastian Möller and Gabriel Curio
Volume 500(Supplement 1),
In telecommunication research, audio quality is typically assessed with behavioral tests. Neurophysiological data can complement these as an objective and non-intrusive measure, potentially revealing neuronal differences in quality processing below the threshold of conscious perception that might affect a user’s long-term satisfaction. Recently, subconscious processing of noise in phonemes was found in event-related potentials (ERPs). The present EEG study (N= 8) applies this approach to a more realistic setting. In a forced choice task, subjects had to rate whether a given word was of maximal quality or degraded. Stimuli were presented either in wideband quality (60%) or were impaired by four progressive levels of bit rate reduction, using a standard telecommunication codec. The ERP analysis allowed qualifying those trials where subjects correctly indicated a loss of quality: The higher ‘neural uncertainty’ involved in detecting more subtle degradations is reflected in a decreased amplitude of the P3 component. Additionally, we used a linear classifier to single out trials where quality impairment was not reported, but still evoked an ERP pattern
similar to when it was processed consciously (three subjects).
Thus, the approach demonstrates that even if no quality impairment is noted consciously, the degradation can still be processed in the cortex. Concluding, the ERP paradigm previously developed for noisy phonemes can be transferred successfully to full words degraded by realistic broadcast limitations.