Response preferences for "what" and "where" in human non-primary auditory cortex.

Primate studies suggest the auditory cortex is organized in at least two anatomically and functionally separate pathways: a ventral pathway specializing in object recognition and a dorsal pathway specializing in object localization. The current experiment assesses the validity of this model in human listeners using fMRI to investigate the neural substrates of spatial and non-spatial temporal pattern information. Targets were differentiated from non-targets on the basis of two levels of pitch information (present vs. absent, fixed vs. varying) and two levels of spatial information (compact vs. diffuse sound source, fixed vs. varying location) in a factorial design. Analyses revealed spatially separate responses to spatial and non-spatial temporal information. The main activation associated with pitch occurred predominantly in Heschl's gyrus (HG) and planum polare, while that associated with changing sound source location occurred posterior to HG, in planum temporale (PT). Activation common to both pitch and changing spatial location was located bilaterally in anterior PT. Apart from this small region of overlap, our data support the anatomical and functional segregation of 'what' and 'where' in human non-primary auditory cortex. Our results also highlight a distinction in the sensitivity of anterior and posterior fields of PT to non-spatial information and specify the type of spatial information that is coded within early areas of the spatial processing stream.