Successful measurement of the mismatch negativity despite a concurrent movie soundtrack: Reduced amplitude but normal component morphology

•The mismatch negativity (MMN) is observed but with reduced amplitude when EEG is recorded while listening to a movie soundtrack.•The movie soundtrack acts as a low-level masking noise.•MMN amplitude increases as the sound-to-noise ratio of the MMN-critical tones over the soundtrack increases.

ObjectiveTo examine the mechanisms responsible for the reduction of the mismatch negativity (MMN) ERP component observed in response to pitch changes when the soundtrack of a movie is presented while recording the MMN.MethodsIn three experiments we measured the MMN to tones that differed in pitch from a repeated standard tone presented with a silent subtitled movie, with the soundtrack played forward or backward, or with soundtracks set at different intensity levels.ResultsMMN amplitude was reduced when the soundtrack was presented either forward or backward compared to the silent subtitled movie. With the soundtrack, MMN amplitude increased proportionally to the increments in the sound-to-noise intensity ratio.ConclusionMMN was reduced in amplitude but had normal morphology with a concurrent soundtrack, most likely because of basic acoustical interference from the soundtrack with MMN-critical tones rather than from attentional effects.SignificanceA normal MMN can be recorded with a concurrent movie soundtrack, but signal amplitudes need to be set with caution to ensure a sufficiently high sound-to-noise ratio between MMN stimuli and the soundtrack.