Cortical representations of temporal structure in sound

Pitch and spatial width are two sound attributes that can be coded by temporal acoustic structure. In this study, periodicity pitch was created by temporal iteration in a regular-interval noise, whereas spatial width was determined by the degree of interaural correlation. Previous results suggest that nonprimary auditory cortex, particularly lateral Heschl's gyrus (HG), plays an important role in the analysis of both acoustic properties. It has been argued that this role might reflect a common computational process. One proposed candidate is that of integrating the temporal pattern information across frequency channels. This paper reports the results of a systematic test for whether different classes of temporal structure do indeed engage a common neural architecture in the human auditory cortex by presenting both classes of sound stimuli to a single group of listeners. Activations related to the pitch and spatial width of the sound were partly co-localized in two distinct cortical regions: close to lateral HG and in planum temporale (PT). Lateral HG was more responsive to temporal pitch than to spatial width. This difference plus the variability across listeners for spatial width dispute the claim that the activity in lateral HG reflects a common neural computational step that encodes the temporal patterns associated with pitch and spatial width. Rather, the activity patterns are consistent with a role for lateral HG in perceptual analysis as opposed to temporal acoustic structure. In PT, the superadditive relationship between pitch and spatial width is also consistent with the concept that the auditory cortex plays an important role in integrating different classes of sound information to form auditory objects.