Rapid cross-sensory adaptation of self-motion perception

Perceptual adaptation is often studied within a single sense. However, our experience of the world is naturally multisensory. Here, we investigated cross-sensory (visual vestibular) adaptation of self motion perception. It was previously found that relatively long visual self-motion stimuli (greater or equal to 15s) are required to adapt subsequent vestibular perception, and that shorter duration stimuli do not elicit cross sensory (visual vestibular) adaptation. However, it is not known whether several discrete short duration stimuli may lead to cross sensory adaptation (even when their sum, if presented together, would be too short to elicit cross sensory adaptation). This would suggest that the brain monitors and adapts to supra modal statistics of events in the environment. Here we investigated whether cross sensory (visual vestibular) adaptation occurs after experiencing several short (1s) self-motion stimuli. Forty five participants discriminated the headings of a series of self motion stimuli. To expose adaptation effects, the trials were grouped in 140 batches, each comprising three prior trials, with headings biased to the right or left, followed by a single unbiased test trial. Right, and left biased batches were interleaved pseudo randomly. We found significant adaptation in both cross sensory conditions (visual prior and vestibular test trials, and vice versa), as well as both unisensory conditions (when prior and test trials were of the same modality, either visual or vestibular). Fitting the data with a logistic regression model revealed that adaptation was elicited by the prior stimuli (not prior choices). These results suggest that the brain monitors supra modal statistics of events in the environment, even for short duration stimuli, leading to functional (supra modal) adaptation of perception.