Most people with tinnitus also have hearing loss or are more sensitive to sounds, and researchers initially concluded that these were all symptoms of a damaged cochlea.
The trouble is that people without a cochlea can also have tinnitus, Tracking down a physical cause is tricky. Early ideas about the causes focused on the cochlea, the coiled organ of the inner ear where sounds are converted into nerve impulses- even cutting the nerve from the cochlea does not stop the ringing in most cases. Nowadays the focus is more on the auditory pathways.
Just like other brain pathways, the auditory pathways never completely shut down. Even in silence, the auditory system is continually active. A random ‘firing of neurons’ creates a kind of background noise that has to be filtered out before the brain registers it as sound.
Tinnitus may be caused by a breakdown of this filtering system. That might also explain why tinnitus worsens in a quiet environment – there is less noise from the outside world to swamp the background buzz. Yet the auditory pathway does not run in isolation from cochlea to cortex. Other areas of the brain can link up with it and modify the signals as well.
Neurons deprived of decent input from the cochlea may start sprouting in other directions and make new synapses, which would mean that what the brain ‘hears’ may not even travel directly up the auditory pathway.
Connections with the limbic and autonomic systems could help explain why anxiety and stressful moods increase the sensation. In short, the perception of sound can involve every functioning neuron in the auditory pathway as well as inputs from the limbic system and the autonomic nervous system.
The disputes over the causes of and treatments for tinnitus seem set to rumble on for a good while yet. It is still early days for a medicine as a cure.
The Listening Training has proven to be effective in many cases, mainly because of the reduction of stress to the overall nervous system.
People are often not aware how much stress they carry around with them day after day. And even if the tinnitus does not totally disappear, it does become much easier to bear when you are relaxed and have learnt to redirect your focus to more pleasurable things.