Shift in sound localization induced by rTMS of the posterior parietal lobe

Neuroimaging studies in human subjects and single-unit recordings in monkeys have suggested the primate posterior parietal cortex (PPC) to be involved in auditory space perception. Here we tested this hypothesis by combining repetitive focal transcranial magnetic stimulation (rTMS) of the right PPC with a task of pointing to free-field-sound stimuli. After a period of 15 min rTMS at 1Hz, subjects exhibited an overall signed error in pointing by 2.5 degrees, directed to the left and downward, with reference to a baseline condition with "sham rTMS". No effects of rTMS on the general precision of sound localization (unsigned errors) were found. Thus, low-frequency offline rTMS may have specifically affected neuronal circuits transforming auditory spatial coordinates in both azimuth and elevation. This is in accordance with the view that the PPC may represent a neural substrate of the perceptual stability in spatial hearing.