Abstract
Emerging evidence suggests commonality between neural mechanisms that encode visual and auditory motion. Following adaptation to unidirectional visual motion, perceived position of a visual stationary stimulus appears offset in the direction opposite to the adapting motion, showing a direct interaction between mechanisms that encode motion and spatial position. In this study, we examine the effects of motion adaptation on the perceived location of subsequently presented stationary stimuli in both auditory and visual domains. Previous studies suggest that motion-induced offsets in position exhibit band-pass velocity tuning, with little or no offsets beyond adapting velocities of 32°/s. By systematically varying adaptor spatial frequency, we demonstrate substantial motion induced shifts up to 128°/s. This suggests that that the differences in tuning limits can be explained by changes in the detectability of adapting stimuli. Using individual head-related-transfer-functions (HRTF) we created auditory motion stimuli in the horizontal plane that could vary in angular velocity, spatial extent and duration. Following adaptation to unidirectional auditory motion, participants made a spatial localisation judgment of a stationary auditory stimulus relative to their internal midline. Consistent with visual findings, all subjects showed a marked direction-dependant shift in perceived auditory position, relative to a “no adaptation” baseline measure. Furthermore, this phenomenon exhibited similar band-pass tuning to that found in the visual domain. Finally, we present data showing that adapting to visual motion results in perceived shifts in stationary auditory stimuli, showing a cross modal interaction of motion and position. Similarities between velocity tuning of shifts for each sensory modality are explored.
RWD, NWR and PVM are supported by the Wellcome Trust.