Everyday, the brain accesses information from various sense organs simultaneously to create a picture" of its environment. This important mixture of information from various sense organs is known as multisensory integration".
Many activities would be difficult to carry out if the brain did not receive information from a number of different sources at the same time. Furthermore, by manipulating multisensory integration, one can create illusions of perception. One well-known example is the 'ventriloquist effect'. If one hears a voice (for example, from a loudspeaker), and then simultaneously sees a face or a mouth moving to speak, then the voice appears to come from the mouth even when, in the case of ventrioloquist, the mouth belongs to a dummy. Similar effects are known to occur with the other senses: if someone rubs their hands together, they produce a noise that one can use to determine if their hands are dry or raw. If the sound, however, is cleverly manipulated, then subjects make completely different guesses about the condition of their skin.
The auditory cortext in action. The picture was created using functional magnetic resonance imaging. The colored points indicate regions which react with strong activation to particular impulses. A: tactile stimulation of the hand. B: auditory stimulation. C: simultaneous tactile and auditory stimulation. In C there is more activity than in B, which suggests that the processing of the auditory stimulus is influenced by the tactile stimulation.
Picture: Max Planck Institute for Biological Cybernetics