Differential cortical processing of location and pitch changes in dichotic pitch.

The objective of this study was to determine whether the auditory mismatch negativity can be elicited by changes in spatial and nonspatial cues within dichotic pitches. Participants were presented with blocks of standard dichotic pitch stimuli in which location or pitch was occasionally varied. A mismatch negativity was reliably elicited by deviant locations; in contrast, no measurable mismatch negativity response was found for deviant pitches. A separate psychophysical screening procedure ruled out the possibility that participants could not hear the pitch deviations. The results indicate that spatial and nonspatial features of dichotic pitch receive differential processing at a preattentive level of analysis within the auditory system and are supportive of recent notions of dual processing streams in audition.