Neural mechanisms for integrating information from multiple senses

Information from different senses is continually synthesized by the brain. It is the product of this "multisensory" synthesis that determines our perception and overt behavior. The psychological literature is replete with examples of how sensory cues in one modality can alter perceptual and behavioral responses to another, yet little is known about the neural mechanisms by which multisensory synthesis is accomplished. Recently, neurons in the superior colliculus (SC) have been used as a model for understanding multisensory integration at the single neuron level. SC neurons show marked enhancements in their activity when cross-modal stimuli are coincident in time and space, and can be rendered unresponsive to stimuli that are disparate in time and/or space. It appears that multisensory integration favors the enhancement of signals derived from the same events and the suppression of stimuli derived from different events. The neural circuitry essential for these neural processes and the principles governing them are discussed.