Abstract:

In humans, visual and auditory spatial information arise in different reference frames, with auditory information being head-centered based on interaural cues, whereas visual information derives from the retinal activation, an eye-centered signal. This study investigated whether visually-guided recalibration of auditory space occurs in a head-centered, eye-centered or a hybrid (combination of both) reference frame. Subjects made saccades to combined auditory-visual targets. The visual component of the target was displaced laterally by 5(degrees). Interleaved auditory-only trials served to evaluate the effect of the mismatched visual stimulus on auditory space. To dissociate head- from eye-centered reference frames, the initial fixation position of the eyes was varied. The results reflected contributions of both coordinate frames. First, the magnitude of the induced shift was affected by the eye-centered location of the targets, but occurred at a consistent location in head-centered space. Second, when subjects were trained using one fixation position and tested using a different fixation position, the magnitude of the induced shift was reduced, but the target locations that showed the greatest shift did not move. The hybrid nature of these effects is reminiscent of recent demonstrations of eye position modulation in the auditory pathway of non-human primates. [Work supported by NIH]