Jörg Lewald (1,2), Klaus A J Riederer (3,4), Tobias Lentz (5), Ingo G Meister (6,7)
(1) Leibniz Research Centre for Working Environment and Human Factors, Institute for Occupational Physiology at the University of
Dortmund, Ardeystr. 67, D-44139 Dortmund, Germany
(2) Department of Cognitive Psychology, Faculty of Psychology, Ruhr University Bochum, D-44780 Bochum, Germany
(3) Laboratory of Acoustics and Audio Signal Processing, Helsinki University of Technology, FI-02015 HUT, Finland
(4) KAR, Isokaari 40, FI-00200 Helsinki, Finland
(5) Institute of Technical Acoustics, RWTH Aachen University, Neustr. 50, D-52066 Aachen, Germany
(6) Department of Neurology, RWTH Aachen University, Pauwelsstr. 30, D-52074 Aachen, Germany
(7) Department of Neurology, University Hospital Cologne, Kerpener Str. 62, D-50924 Cologne, Germany
Email: joerg.lewald at rub.de
This functional magnetic resonance imaging study was focused on the neural substrates underlying human auditory space perception. In order to present natural-like sound locations to the subjects, acoustic stimuli convolved with individual head-related transfer functions were used. Activation foci, as revealed by analyses of contrasts and interactions between sound locations, formed a complex network, including anterior and posterior regions of temporal lobe, posterior parietal cortex, dorsolateral prefrontal cortex and inferior frontal cortex. The distinct topography of this network was the result of different patterns of activation and deactivation, depending on sound location, in the respective voxels. These patterns suggested different levels of complexity in processing of auditory spatial information, starting with simple left ŕ right discrimination in the regions surrounding the primary auditory cortex, while the integration of information on hemispace and eccentricity of sound may take place at later stages. Activations were identified as being located in regions assigned to both the dorsal and ventral auditory cortical streams, that are assumed to be preferably concerned with analysis of spatial and non-spatial sound features, respectively. The finding of activations also in the ventral stream could, on the one hand, reflect the well-known functional duality of auditory spectral analysis, that is, the concurrent extraction of information based on location (due to the spectrotemporal distortions caused by head and pinnae) and spectral characteristics of a sound source. On the other hand, this result may suggest the existence of shared neural networks, performing analyses of auditory ‘higher-order’ cues for both localization and identification of sound sources.
Keywords: auditory space perception, functional magnetic resonance imaging, sound localization, spatial hearing.