Sound In The Brain

The ear sends impulses to the brain through the auditory nerve to the ventral cochlear nucleus. Most of these signals are projected to a structure called the superior olivary complex, which is involved in determining the location of sounds. This area sends messages to another structure called the inferior colliculus, which is in the midbrain; at this point, most of the auditory in one side of the brain has come from the ear on the opposite side. This information passes through the thalamus and is sent to the temporal lobe of the cerebral cortex, which is involved in decoding the information sent from the ears and processing the more complex aspects of sounds.

Higher frequencies are processed by a system called "place coding." As already mentioned, specific portions of the basilar membrane move in response to certain frequencies of sound. The brain recognizes sounds of moderate to high frequency by the portion of the basilar membrane that is moving.

How place coding takes place.

However, specific regions of the basilar membrane do not move in response to sounds with a low pitch. These sounds are identified by "rate coding." Certain cells at the apical end of the basilar membrane move along with the liquid in the cochlea. It is thought that the brain perceives sounds with lower frequencies using the frequency of oscillation of these cells.