Processing of auditory spatial cues in human cortex: An fMRI study

The issue of where in the human cortex coding of sound location is represented still is a matter of debate. It is unclear whether there are cortical areas that are specifically activated depending on the location of sound. Are identical or distinct cortical areas in one hemisphere involved in processing of sounds from the left and right? Also, the possibility has not been investigated so far that distinct areas have a preference for processing of central and eccentric sound locations. The present study focussed on these issues by using functional magnetic resonance imaging (fMRI). Activations evoked by left, right and central sounds were analysed separately, and contrasts were computed between these conditions. We did not find areas, which were involved in the processing of exclusively left, right or central sound positions. Large overlapping areas rather were observed for the three sound stimuli, located in the temporal, parietal and frontal cortices of both hemispheres. This result argues for the idea of a widely distributed bilateral network accessing an internal representation of the body to encode stimulus position in relation to the body median plane. However, two areas (right BA 40 and left BA 37) also were found to have preferences for sound position. In particular, BA 40 turned out to be significantly more activated by processing central positions, compared to eccentric stimuli. In line with previous findings on visual perception, the latter observation supports the assumption that the right inferior parietal cortex may be preferentially involved in the perception of central stimulus positions in relation to the body.