Jean Pie

We sample the world around us with many senses - vision, touch, audition, and others - and sensory information enters the brain via physically separate pathways, yet we experience one unified percept of the world. We constantly interact with our multisensory surroundings, combining inputs and coordinating outputs in relation to multiple sensory modalities. How is the brain implementing the integration of multiple senses?

In this thesis, I studied how multisensory evidence is combined for stimulus detection and how multisensory context shapes sensory processing. In Chapter 2, we developed an audiovisual detection task for mice and showed they can linearly combine visual and auditory information at the behavioral level, emphasizing the validity of this animal model for studying multisensory processing. In Chapter 3, we explored the mouse posterior parietal cortex as a candidate area for the combination of visual and tactile evidence. While we did not find multisensory-specific neuronal activity, we found stimulus detection correlates and uncovered this area’s causal involvement in attentive visuotactile decision-making independently of sensory modality. In Chapter 4, we report that adding an extra relevant sensory modality to the task demands of a unisensory task, extended the temporal window during which the primary visual cortex was causally involved in visual perception, showing that multisensory context altered cortical activity and dynamics. Finally, we zoom in on the neuron-level mechanisms of sensory processing by studying cell type specific function. In Chapter 5, we reveal that layer 5 pyramidal tract neurons in the rat primary somatosensory cortex, but not other cell types, encode touch via bursting activity, paving the way to explore the role of cell types in processing both multisensory stimuli and contexts. Taken together, these findings advance our understanding of the neural principles that support multisensory processing, from behavior to circuits to single-cell function.