[THE EFFECTS AND AFTEREFFECTS OF A SOUND SOURCE APPROACHING AND WITHDRAWING ON POSTURAL RESPONSES IN HUMANS ]

The multimodal influence of the auditory motion adaptation was studied until now on visual perception only, however, the auditory motion adaptation can influence other modalities. This study is the first attempt to investigate postural aftereffects to 45-second adaptation to approaching or withdrawing sound images, that were simulated by rhythmic sequences of tone pulses changed linearly in amplitude and frequency in the free field. The oscillations of the center of pressure in the sagittal plane with the rhythm of stimuli were detected. These oscillations were more noticeable for approaching than for withdrawing stimuli and resulted in an increase of the length of the trajectory of the center of pressure and average linear velocity of its motion. The center of pressure shifted in the direction of the sound motion during listening to approaching sound images, and to the opposite direction during 20 s after its turning off. The shift to the opposite direction demonstrates typical negative aftereffect. The data are in accordance with the results of studies of postural responses to moving visual stimuli, where the «negative» effect was also revealed.