Traditionally, perceptual research has been compartmentalized into distinct and isolated categories according to individual modalities (i.e., visual, auditory, haptic, proprioceptive, vestibular, etc.).  This modular approach has treated individual sensory and motor processing as involving largely independent systems.  However, recently investigators are recognizing the importance of understanding cross-modal interactions and how they relate to perception and behaviour.

Much of the multisensory research up until this point has focused upon tasks involving discrete stimulus presentations in near body space. Such cue interactions of interest have included: visual-auditory integration, visual-proprioceptive integration, or visual-haptic integration. It is important, however, to investigate multisensory integration from the perspective of large-scale self-motion through action space. Unlike traditional approaches to examining the integration of two specific cues at a particular instance in time, navigating through one’s environment requires the dynamic integration of several cues across space and over time (i.e., visual flow, lower-limb proprioception, and vestibular information).  Understanding the principles underlying multimodal integration in this context of unfolding cue dynamics is very important as it provides insight into an important category of multisensory processing.

◘ Multi-sensory integration in the estimation of distance traveled
◘ Contribution of inertial information to the perception of walking speed
◘ Perception of visual speed while walking
◘ Adaptive treadmill control
◘ Vestibular perception is slow
◘ Perceived object stability
◘ Shape from shading

Vestibular perception is slow

Involuntary physical responses to vestibular stimulation are very fast. The vestibulo-ocular reflex, for example, occurs approximately 20ms after the onset of vestibular stimulation (Lorente de No, 1933). Surprisingly, despite these fast responses, reaction time (RT) to the perceived onset of vestibular stimulation occurs as late as 438ms after galvanic vestibular stimulation, which is approximately 220ms later than RTs to visual, somatosensory and auditory stimuli (Barnett-Cowan & Harris, 2009). Here we investigate why vestibular perception is slow. An initial investigation tested the hypothesis that RTs to natural vestibular stimulation (as opposed to galvanic vestibular stimulation) are also slow. Participants were passively moved forwards using the Stewart motion platform and were asked to press a button relative to the onset of physical motion. RTs to auditory and visual stimuli were also collected. RTs to physical motion occurred significantly later (about 100ms) than RTs to auditory and visual stimuli. Event related potentials (ERPs) were simultaneously recorded where the onset of the vestibular-ERP in both RT and non-RT trials occurred about 200ms or more after stimulus onset while the onset of the auditory- and visual-ERPs occurred less than 100ms after stimulus onset. All stimuli ERPs occurred approximately 135ms prior to RTs. These results provide further evidence that vestibular perception is slow compared to the other senses and that this perceptual latency may be related to latent cortical responses to physical motion. The next phase of our investigations will assess reaction time and ERP responses to passive motion while manipulating peak velocity, acceleration and jerk. Perceived simultaneity of passive motion paired with moving visual stimuli will also be assessed.

REFERENCE
◘ Lorente de No R (1933): Vestibulo-ocular reflex arc. Arch Neurol Psychiat 30:245-291

◘ Barnett-Cowan, M. and L. R. Harris: Perceived timing of vestibular stimulation relative to touch, light and sound. Experimental Brain Research 198(2-3), 221-231

◘ Barnett-Cowan, M., H. Nolan, J. S. Butler, J. J. Foxe, R. B. Reilly and H. H. Bülthoff: Reaction time and event-related potentials to visual, auditory and vestibular stimuli. Vision Sciences Society 2010