ASSESSING MULTISENSORY INTEGRATION WITH ADDITIVE FACTORS AND FUNCTIONAL MRI

  • Thomas W. James
  • Ryan A. Stevenson
  • Sunah Kim

Abstract

The topic of this presentation is the use of additive-factor designs in combination withfunctional MRI to assess multisensory integration. Unisensory and multisensory stimuli werepresented across two different pairings of sensory systems, audio-visual (AV) and visuohaptic(VH). In addition to stimulus modality, signal-to-noise ratio (SNR) was included as anadditive factor. Previous research investigating the effect of SNR on sensory integration hasdocumented an effect called inverse effectiveness, where the multisensory gain increases withdecreasing SNR. Potential sites of multisensory convergence were mapped for each sensorypairing and were found to be non-overlapping, suggesting that the neural mechanisms ofintegration are specialized for each unique pairing of sensory systems. Evidence of inverseeffectiveness was found at all convergence sites, regardless of whether they were AV or VH.This result suggests that inverse effectiveness is a general characteristic of multisensoryintegration, regardless of the sensory pairing. The results also showed that a single-factoradditive model of multisensory integration produced different outcomes at different levels ofSNR. Based on this last result, we conclude that an additive-factors approach to assessingmultisensory integration will provide more reliable inferences than single-factor designs.
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