Natural behaviours, and hence neuronal populations, often combine multiple sensory cues to improve stimulus detectability or discriminability as we explore the environment. Here we review one such example of multisensory cue integration in the dorsal medial superior temporal area (MSTd) of the macaque visual cortex. Visual and vestibular cues about the direction of self-motion in the world (heading) are encoded by single multisensory neurons in MSTd. Most neurons tend to prefer lateral stimulus directions and, as they are broadly tuned, are most sensitive in discriminating heading directions around straight forward. Decoding of MSTd population activity shows that these neuronal properties can account for the fact that heading perception in humans and macaques is most precise for directions around straight forward, whereas heading sensitivity declines with increasing eccentricity of the reference direction. Remarkably, when heading is specified by both cues simultaneously, behavioural precision is improved in a manner that is predicted by statistically optimal (Bayesian) cue integration models. A subpopulation of multisensory MSTd cells with congruent visual and vestibular heading preferences also combines the cues near-optimally, establishing a potential neural substrate for behavioral cue integration.
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