A second noise burst (S2) was presented 500 ms after the offset of S1. After a delay of 1000 ms, a noise burst (S1) was presented at one of three possible locations and one of three possible pitches that excluded the two extreme locations and the two extreme pitches. Each trial began with a binaural warning tone (1000 Hz, 500-ms duration, 5-ms rise/fall time). Participants performed a delayed match-to-sample task in which the first acoustic stimulus (S1) was held in memory (for 500 ms) for comparison with the second (S2) stimulus. These findings are analogous to the “what” and “where” segregation of visual information processing, and suggest that a similar functional organization exists for processing information from the auditory modality. The converging evidence from two independent measurements of dissociable brain activity during identification and localization of identical stimuli provides strong support for specialized auditory streams in the human brain. Differential task-related effects on event-related brain potentials (ERPs) were seen in anterior and posterior brain regions beginning at 300 ms poststimulus and lasting for several hundred milliseconds. Conversely, identifying the location of S2 relative to S1 generated greater activation in posterior temporal cortex, parietal cortex, and the superior frontal sulcus. Relative to location, pitch processing generated greater activation in auditory cortex and the inferior frontal gyrus. In the location task, participants were asked to localize S2 relative to S1 (i.e., leftward, same, or rightward). In the pitch task, participants indicated whether S2 was lower, identical, or higher in pitch than S1. Participants performed an S1–S2 match-to-sample task in which S1 differed from S2 in its pitch and/or location. ![]() The extent to which sound identification and sound localization depend on specialized auditory pathways was examined by using functional magnetic resonance imaging and event-related brain potentials.
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