The cortical distribution of multisensory neurons was modulated by multisensory experience.

Previous studies have indicated a sparse distribution of multisensory neurons in the transition zones between cortical areas associated with specific sensory modalities. However, little is known about the distribution and functional properties of such neurons. The bimodal visual-auditory neurons in the transition area between visual and auditory cortices in rats were examined to determine whether these neurons are modulated by simultaneous input from visual and auditory modalities. Visual-auditory neurons were found to have a non-uniform distribution within this region, instead gathering together and forming a small zone. Electrophysiological recordings revealed that visual-auditory neurons possess integrative characteristics similar to neurons of the superior colliculus, a midbrain structure in the visual pathway. Exposing adult animals to combined visual and auditory stimuli resulted in an expansion of bimodal neuron distribution in the visual-auditory transition area. These effects were more pronounced in young animals; in this case, the distribution of visual-auditory neurons extended past the limits of the transition area and invaded the flanking modality-specific cortical areas. These results provide a direct demonstration of the role of sensory experience in shaping cortical structure, which can have implications for neuronal integration and cognitive function.