Dynamics of intra- and inter-regional activities of the auditory 'Where' pathway during sound localization: An fMRI...

Previous neuroimaging studies suggested that sound localization was accomplished by a cortical "where" pathway, which originated from auditory cortex and went through parietal and prefrontal regions. While previous studies focus on regional activity and functional connectivity patterns of such cortical network, the dynamics of intra- and inter-regional activities of auditory "where" pathway during sound localization remains unclear. In the present study, we investigate such question by applying hemodynamic response function (HRF) analysis and dynamic causal modeling (DCM) to functional magnetic resonance imaging (fMRI) data collected as participants passively listened to auditory stimuli from five horizontal locations (-90°, -45°, 0°, 45°, 90°). HRF analysis revealed hemispheric asymmetry of regional dynamics and potential bottom-up information flow along the "where" pathway during sound localization. DCM demonstrated that sound localization induced excitatory modulatory effects along the ascending auditory pathway and inhibitory modulatory effects along the descending auditory pathway. In addition, modulation of interhemispheric effective connectivity was found between bilateral Heschl's gyri. Overall, the present study probes dynamics of intra- and inter-regional activities of auditory "where" pathway during sound localization, which provides novel insights into the integration of spatial information within the cortical auditory network.