Multisensory integration enhances audiovisual responses in the Mauthner cell

Abstract

ABSTRACTMultisensory integration combines information from multiple sensory modalities to create a coherent perception of the world. In contexts where sensory information is limited or equivocal, it also allows animals to integrate individually ambiguous stimuli into a clearer or more accurate percept and, thus, react with a more adaptive behavioral response. Although responses to multisensory stimuli have been described at the neuronal and behavioral levels, a causal or direct link between these two is still missing. In this study, we studied the integration of audiovisual inputs in the Mauthner cell, a command neuron necessary and sufficient to trigger a stereotypical escape response in fish. We performed intracellular recordings while presenting a diverse range of stimuli to determine which stimulus properties affect their integration. Our results show that stimulus modality, intensity, temporal structure, and interstimulus delay affect input summation. Mechanistically, we found that the distinct decay dynamics of feedforward inhibition triggered by auditory and visual stimuli can account for certain aspects of input integration. Altogether, this is the first study to investigate multisensory integration in a cell of clear behavioral relevance and provides a phenomenological and mechanistic characterization of how multisensory integration depends on stimulus properties.SIGNIFICANCE STATEMENTIn real-world scenarios where sensory information can be ambiguous, mechanisms that reduce the uncertainty and increase information about potential threats is of critical importance. During multisensory integration, independent signals from an event are combined to form a percept with enhanced information. The Mauthner cell is a paramount example of an identified brainstem neural circuit in fish that decides whether or not to execute a fast escape, directly contributing to the animal survival. Here we show that themechanistic implementation of multisensory integration at a single-cell level inthe Mauthner cell results from properties of the sensory inputs, restrictions imposed by intrinsic properties, neuronal architecture and network inhibitory effects. Importantly, this multisensory response enhancement has direct and unequivocal impact in animal behavior and survival.