How tinnitus starts
Purpose of hearing
Sound has great importance for monitoring of our environment. Animal’s hearing, which lives in constant fear of their lives because of attacks from predators, must be very sensitive. The ability of animals to develop extremely acute hearing, by which they could detect the very small sounds of an attacker a long way off, contributes to the survival of that animal. Sound warning signals produce acute anxiety, prompting appropriate action to avoid an attack or attack. This is called survival reflex. We respond in the same way to the sound of a car horn, by automatically stepping back from the street. Some sounds can be identified as warning signals, while others can evoke a feeling of security or pleasure. We have this experience every day with sounds that alarm us or sounds that soothe us such as music, or the sounds of nature. Many sounds naturally evoke strong emotions of one sort or another.
How we hear
The conscious awareness of sound is located near the surface of the brain when patterns of electrical activity go from hearing nerve to the part of the brain - auditory cortex. The hearing nerve has about 30,000 fibers, and patterns of electrical activity in these fibers are matched with other patterns, which are held in the auditory, or hearing memory. The inner ear, which changes sound waves into these electrical patterns, is a surprisingly noisy place. This continuous mechanical and electrical activity in 17,000 hair cells can be monitored with sensitive, computer-enhanced, listening devices. This noise is called otoacoustic emissions. Most of what we hear is a sequence of different sounds, like speech or music. In infancy, new sound experiences are stored in an information-hungry, but relatively empty auditory cortex. Later, there is a continuous process of matching familiar memory patterns with those coming from the ear.
Each time a pattern from the ears is matched with a pattern in the auditory memory we have the experience of hearing and recognizing a sound. Putting together these matched patterns starts a process of evaluation. Another part of the brain close to this initial hearing center is involved in the meaning of what we hear, and in interpreting the language. If it’s a foreign language, we can hear the sound, but we may not understand the meaning.
When a sound has special or critical meaning, like the baby waking at night, or the creaking of a floorboard, or the sound of our first name, we respond to it in an automatic manner, even if the volume is very soft. This happens after a short learning period, but the responses can remain as strong during the whole life. During sleep, the conscious part of the brain is ‘shut down’ so we don’t hear, see or feel anything. However, the mother still wakes to the baby stirring even though she has just slept through a thunderstorm. This shows that weak patterns of sound, if they have great significance and meaning, can be detected by subconscious pathways or filters, between ear and part of the brain - auditory cortex, even during sleep. These filters can enhance and amplify important sounds, and at the same time, suppress or habituate sounds of no interest.
Conditioned reflex responses
Conditioned reflex responses trigger activity outside the auditory system. There are large numbers of connections with the limbic system (see opposite) which is concerned with emotion and learning. It also stimulates the autonomic nervous system which activates the body, to prepare for any eventuality. In situations of danger or perceived threat, the familiar ‘fight or flight’ response is triggered. This involves high levels of autonomic function; tense muscles raised heart and breathing rates, sweating - the complete opposite to the state of relaxation. They rightly preclude sleep, or concentration on other, less important tasks. Limbic and autonomic responses to things we always dislike, involve the same mechanisms, but are less strong, and are called aversive conditioned responses. A universal aversive response occurs with the sound of nails scraping across a piece of glass. Every sound that we hear and learn the meaning of, has an “emotional label” attached to it, which may change from time to time according to how we feel, and the context in which we hear it. For example, the sound of the next-door television set may be either acceptable, or unpleasant and intrusive, depending on whether it belongs either to a well-loved friend or relation, or a neighbor that we don’t like.
The meaning of tinnitus sounds
Heller and Bergman performed a simple experiment. They placed 80 tinnitus free students (university members) in a soundproofed room for 5 minutes each, asking them to report on any sounds that might be heard. The subjects thought they might be undergoing a hearing test, but in fact, they experienced 5 minutes of total silence. 93% reported hearing buzzing, pulsing, whistling sounds in the head or ears identical to those reported by tinnitus sufferers. This simple experiment shows almost anyone can detect background electrical activity present in every living nerve cell in the hearing pathways as a sound. Although some areas of the auditory system may be more active than others, every neuron will contribute to some extent to the final perception of tinnitus. These electrical signals are not evidence of damage, but a compensatory activity that occurs all the time in the auditory system of each one of us. Compensation can occur as a response to changes in our sound environment (e.g. silence) to hearing loss which may be a natural part of aging, or to exposure to sudden noise. Of those who experience persistent tinnitus, population studies have shown that about 85% do not find it intrusive, disturbing or anxiety-provoking, which something tinnitus sufferers find very hard to believe. The reason for this is not so much because of the quality or loudness of the tinnitus is different. In fact, it was found that tinnitus is of a very similar type of sound in those who are bothered by it and those who are not.
The main difference is that those who find tinnitus troublesome, evaluate and perceive it as a threat, or an annoyance. The volume is the same. Tinnitus may also emerge for the first time when something unpleasant or frightening is happening to us. In these situations, tinnitus is classified as a warning signal, relating either to a bad experience or to negative thoughts about its meaning or outcome. Just as an animal is alerted to danger by the sound of a predator, and focuses solely on that sound to survive, so those who consider that tinnitus is a threat or warning signal are unable to do anything but listen to it. It is part of the mechanism that all animals have developed for self- preservation, although clearly in this situation it is not working to our advantage. Many people complain of the loss of silence, something they previously greatly treasured and enjoyed, before tinnitus became persistent. Tinnitus becomes part of the bereavement for this loss. What happens, even in mild cases of persistent tinnitus, is that a conditioned response/reaction is set up to the tinnitus sound. As the conditioned response is part of the subconscious brain, and automatic, what you may be thinking about tinnitus at any time, is irrelevant to the reaction produced. Moreover, it is the reaction to tinnitus, which is creating distress, not the tinnitus itself - another difficult concept for some. The degree to which unpleasant feelings about tinnitus (from the limbic system) and increased tension (from autonomic system stimulation) are experienced, dictates the severity of the tinnitus. The loudness and quality of the sound heard is irrelevant.
Tinnitus as a new experience
When tinnitus first emerges, to the auditory system, it is a new signal, and as such there are no memory patterns and no means of categorizing it. Any new experience produces an ‘orienting response’ where we are forced to pay attention until the signal is classified and understood. Until proper evaluation has been undertaken of what tinnitus means, it will be regarded with understandable suspicion. Many ‘sufferers’ only experience mild annoyance from tinnitus because of this orienting response, but it may be sufficient to promote the need to seek help. A typical, and reasonable anxiety is ‘will it get worse?’ or ‘what happens if it goes on forever?’
Tinnitus as a threat
For many sufferers, tinnitus is quite threatening. Some people fear that tinnitus means they have some kind of serious illness. Others are convinced that the experience of ‘disco tinnitus’ means permanent damage to the ear, rather than temporary protective changes, which are normal and universal. There are patients who worry about the possibility that tinnitus means they have a brain tumour, blood clot, or some serious mental illness. Many people fear that tinnitus will get louder, continue forever, and cannot be stoped. The concept that tinnitus is invading one’s ‘right to silence’ constitutes a threat, very like the territorial invasions that all animals experience. It is often feared that tinnitus will continue to spoil peace and quiet, interfere with concentration at work, quiet recreational activity and the ability to sleep at night.
Unfortunately, these fears may be enhanced by professional advice, or reports from other sufferers, who have had a bad reaction to tinnitus. Many doctors and other professionals still advise patients that there is nothing that can be done about tinnitus, and that it will go on forever. Other people fear that tinnitus may mean that their hearing is becoming impaired. Tinnitus may be the consequence of a mild age-related hearing impairment, rather than the other way around. It is still only twice as common in hearing impairment, as in normal hearing. In any event, the threatening qualities of the tinnitus are enhanced by beliefs and negative ideas about tinnitus or associations that have been formed, not any physical changes that may or may not have occurred.
Finally, many tinnitus sufferers are angry about the treatment, or lack of treatment, or inappropriate advice that they have received. They may feel guilty for having submitted to treatment, which they think, is the cause of their tinnitus. Fear, anger and guilt are very powerful emotions, which are intended to enhance survival-style, conditioned reflex activity, and consequently these emotions greatly increase attention on the tinnitus. In our experience, tinnitus improves when the patient overcomes these feelings and stops dwelling on thoughts of injustice...*