Attentional modulation of the mismatch negativity elicited by frequency differences between binaurally presented tone bursts

We examined the attentional sensitivity of the frequency-change mismatch negativity (MMN). Subjects listened to a binaural mixture of a narrative and a series of tone bursts that included 1200-Hz standards and two deviants (1000 and 1400 Hz). In the attend-tones condition, subjects responded to one deviant and ignored the narrative. In the attend-words condition, subjects responded to target words in the narrative and ignored the tones. Event-related potentials (ERPs) were recorded for the tones, and difference waves (deviant ERPs minus standard ERPs) were computed. Two negative peaks in the difference waves, DN1 (100-180 ms) and DN2 (200-300ms), overlapped the known scalp distribution and latency of the MMN. Mean DN1 and DN2 amplitudes were greater in the attend-tones condition than in the attend-words condition. These suggest that the frequency-change MMN is modulated by nonspatial shifts of auditory attention.