This chapter discusses the possible mechanisms of tinnitus generation at a neural level. Other chapters review tinnitus causes (Chapter 2) and the hearing system (Chapter 7). Chapter 14 discussed a plan for verifying these possible generation sites for purposes of finding a cure. Here, we focus on the possible mechanisms of sensorineural tinnitus.

It is known that many types of hearing loss that begin in the cochlea (for example, tinnitus caused by high-level noise exposure) produce tinnitus. For many years it has also been appreciated that the brain must be involved in the coding of tinnitus. There are many causes, many subtypes, and likely, many different mechanisms of tinnitus. One might imagine there might be 100 different mechanisms!

We begin by describing the basic ingredients of how sound is encoded by the nervous system and how this information is transmitted from one nerve to another. We will then describe spontaneous neural activity and sound-evoked activity.

Finally, we will speculate with a few examples of how tinnitus might be initiated and coded in these various sites. Actually, we cannot be certain about the mechanisms of tinnitus, but the intent is to give you an appreciation for some of the possible options that are involved.

Some people call tinnitus a “phantom perception” in the sense that an external sound source is not required for its generation. However, tinnitus is not a phantom sound; it is real and real neural mechanisms are involved in coding your tinnitus, just like they are involved with other sounds.