Grant: Discovery Grants Program - Individual

Our perceptual systems integrate individual pieces of sensory information into unified perceptual gestalts both within and across sensory modalities. Such integration confers myriad benefits, from faster response times to improved speech perception. The long-term goal of my research program focuses on how multisensory integration is instantiated in the brain, and how these sensory processes cascade to influence high-order cognition. My shorter-term goals, and the focus of this proposal, is to explore how integration develops across the lifespan, both behaviourally and neutrally. This integration process is not static, but changes across the lifespan. In development, one learns the regularities of sensory inputs such as their temporal coincidence, and learns cues to determine which signals to integrate. Later in life, more high level, learned associations such as semantic congruency are theorized to play an increased role in integration. We will use a battery of behavioural and imaging paradigms to examine the strength of multisensory integration and two factors that are theorized to differentially influence integration across the lifespan: multisensory temporal processing, a bottom-up influence on integration, and semantic congruence, a top-down influence on integration. In Aim 1, we will apply this battery cross-sectionally across development from 5 years of age to adulthood. In Aim 2, we will use an accelerated longitudinal design to follow this cohort for three years, allowing for causal analyses. In Aim 3, we will move to the other end of lifespan development, as use this battery to assess how the impact of bottom-up and top-down processes change with healthy aging. Behaviourally, we expect a strong link between multisensory temporal processing and integration, but less so semantic congruency. Neurally, we expect strong feedforward connections from lower-level sensory areas into multisensory regions, with multisensory regions projecting towards semantic processing regions. Longitudinally, we expect temporal processing abilities and the neural connectivity between temporal processing and integration at early timepoints will predict subsequent development of integration, establishing a causal link. Finally, with healthy aging, we expect the link between top-down, semantic congruency and integration will strengthen, as temporal processing's influence will wane, reflected by diminished bottom-up inputs into multisensory brain regions, but an increase in top-down projections. This will provide the first foray into how this neural network develops across the lifespan. This research will produce foundational knowledge on the development of multisensory integration across the lifespan behaviourally and neurally. Our basic research findings inform numerous areas of research, including populations showing differences in multisensory perception, including in Autism, ADHD, and dyslexia, as well as to expanding our tools to promote healthy aging.