How well does natural motion induce auditory motion aftereffects?

Abstract

There is evidence that a repeatedly traversing sound source induces motion aftereffects in listeners [D. W. Grantham, Percept. Psychophys. 45, 129–136 (1989)]. Other work has found aftereffects for acoustic attributes often involved in motion, e.g., for level or frequency changes [Reinhardt–Rutland, Percept. Psychophys. 28, 569–571 (1980); Shu et al., Nature 364, 721–723 (1993)]. Few studies, however, have investigated adaptation in the presence of more ecologically valid motion. Normally, stimuli in adaptation paradigms include changes in spectral cues and interaural differences but not the changes in amplitude or frequency that occur with motion under more natural spatial trajectories, e.g., linear approach. The questions arise whether such aftereffects are due to fatiguing neurons mostly sensitive to arbitrary interaural modulations, or are units truly responsive to lawful, natural motion? If integrated motion detectors exist, then including amplitude and frequency changes in adapting stimuli should enhance aftereffects. Subjects will be adapted to three types of stimuli: those with interaural changes only, with amplitude and frequency changes only, or with interaural, amplitude and frequency changes following lawful motion. Greater magnitude aftereffects for latter stimuli or aftereffects induced by middle stimuli may reveal which acoustic attributes hypothesized motion detectors are responsive to. [Work supported by NSF.]