Integration of Sensory Information in the Brain

That sensory cues in one modality affect perception in another has been known for some time, and there are many examples of ‘intersensory’ influences within the broad phenomenon of cross-modal integration. The ability of the CNS to integrate cues from different sensory channels is particularly evident in the facilitated detection and reaction to combinations of concordant cues from different modalities, and in the dramatic perceptual anomalies that can occur when these cues are discordant. A substrate for multisensory integration is provided by the many CNS neurons (eg, in the superior colliculus) which receive convergent input from multiple sensory modalities. Similarities in the principles by which these neurons integrate multisensory information in different species point to a remarkable conservation in the integrative features of the CNS during vertebrate evolution. In general, profound enhancement or depression in neural activity can be induced in the same neuron, depending on the spatial and temporal relationships among the stimuli presented to it. The specific response product obtained in any given multisensory neuron is predictable on the basis of the features of its various receptive fields. Perhaps most striking, however, is the parallel which has been demonstrated between the properties of multisensory integration at the level of the single neuron in the superior colliculus and at the level of overt attentive and orientation behaviour.