Task dependent anatomical connections underlie multisensory processing

Abstract

Our senses interact in daily life through multisensory integration, facilitating perceptual processes and behavioral responses. Numerous multisensory regions have been identified in humans and animals, raising the question of whether a single mechanism can support the dynamic range of experiences and behaviors multisensory processing engenders. The most common neural mechanisms proposed to underlie multisensory processing include anatomical connections directly linking early sensory areas, indirect connections to higher-order multisensory regions, and functional connectivity between cortical areas. Here we examine the relationship between white matter connectivity, as assessed with diffusion tensor imaging and individual differences in two divergent forms of multisensory processing: the redundant-target effect (RTE), in which subjects’ behavior is facilitated by congruent multisensory information, and the sound-induced illusory flash (SIIF) paradigm, in which incongruent multisensory information elicits a novel percept. Behavioral results demonstrated strong intra-subject reliability of the RTE and SIIF paradigms, but no correlation in performance between the two tasks. Consistent with this behavioral finding, we identified distinct anatomical networks underlying these two forms of multisensory processing. Using a whole-brain analysis and contrasting anatomical models of multisensory processing, increased behavioral performance on the RTE was associated with increased connectivity between the superior parietal lobe and early sensory regions. Conversely, increased incidence of illusion on the SIIF paradigm was associated with increased connectivity directly between early auditory and visual areas. These results implicate a broad network of anatomical connections involved in task-dependent multisensory processes.