Many brain regions are now known to respond to input from multiple sensory modalities1. Even primary sensory areas, which were previously thought to respond almost exclusively to area-specific inputs, are now known to reflect multimodal sensory input. These multimodal responses manifest as either physiological response to non-area-specific stimulation alone, or as modulatory enhancement of the area-specific response by non-area-specific stimulation. However, it is unknown whether such multimodal responsivity is modulated by sensory experience. Here we show that multimodal population activity can be altered by patterned audiovisual input. By using voltage-sensitive dye imaging in the Mongolian gerbil (Meriones unguiculatus), we demonstrate that trains of patterned audiovisual stimulation can alter the spatial distribution, propagation patterns and magnitude of population mass action in the mammalian cortex. This modulation depends upon timing contingencies of the auditory and visual stimuli within the patterned stimulus trains. Our results demonstrate, for the first time, that sensory input can induce plasticity in the spatial organization of cortical mass action. These results further suggest that propagating patterns of population mass action may play a role in integrating information from multiple sensory modalities.