Superadditivity in multisensory integration: putting the computation in context.

Single-neuron studies have highlighted dramatic enhancements in neural activity consequent to multisensory integration. Most notable are 'superadditive' enhancements in which the multisensory response exceeds the sum of those evoked by the modality-specific stimulus components individually. Although all multisensory enhancements may have perceptual/behavioral consequences, superadditivity, which suggests a nonlinear combination of modality-specific influences, seems to have had a disproportionate influence within the multisensory literature. This influence has been reinforced by the increasing application of noninvasive techniques such as functional imaging and event-related potential recording, which depend on response nonlinearities to demonstrate underlying multisensory processes. In promoting the idea that many multisensory behaviors may not rely on superadditivity, we consider more recent single-neuron studies that place its incidence in context.