The development of multisensory processes

To understand the development of sensory processes, it is necessary not only to look at the maturation of each of the sensory systems in isolation, but also to study the development of the nervous system’s capacity to integrate information across the different senses. It is through such multisensory integration that a coherent perceptual gestalt of the world comes to be generated. In the adult brain, multisensory convergence and integration take place at a number of brainstem and cortical sites, where individual neurons have been found that respond to multisensory stimuli with patterns of activation that depend on the nature of the stimulus complex and the intrinsic properties of the neuron. Parallels between the responses of these neurons and multisensory behavior and perception suggest that they are the substrates that underlie these cognitive processes. In both cat and monkey models, the development of these multisensory neurons and the appearance of their integrative capacity is a gradual postnatal process. For subcortical structures (i.e., the superior colliculus) this maturational process appears to be gated by the appearance of functional projections from regions of association cortex. The slow postnatal maturation of multisensory processes, coupled with its dependency on functional corticotectal connections, suggested that the development of multisensory integration may be tied to sensory experiences acquired during postnatal life. In support of this, eliminating experience in one sensory modality (i.e., vision) during postnatal development severely compromises the integration of multisensory cues. Research is ongoing to better elucidate the critical development antecedents for the emergence of normal multisensory capacity.