This is Part 1 of a two part blog exploring the underlying neurophysiological model for tinnitus and, in Part 2, how the Neuromonics Tinnitus Treatment treats tinnitus consistent with this model.

Up to 99% of tinnitus cases are subjective tinnitus, ie. tinnitus sound that is only audible to the affected individual and typically linked to hearing loss, damage or dysfunction to noise exposure, aging, exposure to ototoxic drugs, etc. (see blog post, Four Types of Tinnitus).

As described by Jastreboff and Hazell’s seminal 1993 paper, “A neurophysiological approach to tinnitus: clinical implications” [1] and many papers since, subjective tinnitus has three discrete but interrelated and self-reinforcing processes in the development of disturbing tinnitus, all involving neuroplastic changes to the brain:

1. Auditory System & Perception – involves changes within the auditory system which lead to the initial perception of the tinnitus sound;

2. Attentional Filters – involves the attentional filters in the brain which cause someone to pay attention to the perception of tinnitus; and

3. Emotional Response / Reaction – involves the emotional response and the autonomic nervous system which cause an aversive reaction to the tinnitus.

Neural processes that lead to disturbing tinnitus

Auditory system & perception leading to the initial perception of tinnitus

Studies have shown that auditory deprivation causes the auditory system to become more active [2] and more sensitive to sound [3]. Following peripheral hearing damage, for example through noise insult or ototoxic drugs, there are changes in activity levels in the auditory nerves which appear to be centrally mediated [4]. Therefore, the auditory cortex receives more neural input, which it interprets as sound. Essentially, the cortex detects the amplified background neurological activity, and interprets it as the ringing or buzzing sounds perceived in tinnitus. Changes in the auditory cortex also involve reorganization of the tonotopic map [5].

Attentional processes leading to the conscious attention to or awareness of tinnitus

Perceptual filters work on all of our senses all of the time to determine which sensory perceptions should be brought to our conscious attention and which should not. These filters play an important function; they allow the brain to focus on what’s important while preventing us from being overwhelmed by sensory input. These filters recognize specific patterns of neural activity [6], which are constantly being updated and refined through experience. In the case of tinnitus, an importance “label” is applied to the tinnitus sound, such that it is constantly brought to the patient’s attention.

Emotional (limbic) and autonomic nervous system engagement, leading to aversive reaction to tinnitus

For those experiencing disturbing tinnitus, the limbic system of the brain (responsible for our emotional state) and the autonomic nervous system (responsible for the so-called “fight or flight‟ reflex) become engaged in response to the awareness of tinnitus [7]. This causes a stressful state of high arousal and anxiety in response to the awareness of tinnitus, which has a significant impact on our quality of life and general well-being. This reaction also reinforces both the initial perception of and attentional response to tinnitus. This in turn leads to further increase in tinnitus loudness and awareness, which in turn increases the level of stress, etc. in a self-perpetuating viscous cycle that makes tinnitus progressively worse over time.

In Part 2 of this blog, we will discuss how the Neuromonics Tinnitus Treatment directly addresses these interrelated and reinforcing mechanisms to treat tinnitus.

1. Jastreboff, P. & Hazell, J. (1993). A neurophysiological approach to tinnitus: clinical implications. British Journal of Audiology, 27: 7-17.

2. Heller, M.F. & Bergman, M. (1953). Tinnitus aurium in normally hearing persons. Ann Otol Rhinol Laryngol, 62: 73-83.

3. Formby, C., Sherlock, L.P. & Gold, S.L. (2003). Adaptive plasticity of loudness induced by chronic attenuation and enhancement of the acoustic background. The Journal of the Acoustical Society of America, 114: 55-58

4. Reviewed by Eggermont, J.J. & Roberts, L.E. (2004). The neuroscience of tinnitus. Trends in Neurosciences, 27: 676-682.

5. Muhlnickel, W., Elbert, T., Taub, E., & Flor, H. (1998). Reorganization of auditory cortex in tinnitus. Proc. Natl. Acad. Sci. USA, 95: 10340-10343

6. Desimone, R. & Duncan, J. (1995). Neural mechanisms of selective visual attention. Annu. Rev. Neurosci., 18, 193-222; Sussman, E., Winkler, I., Huotilainen, M., Ritter, W., & Naatanen, R. (2002). Top-down effects on the initially stimulus-driven auditory organization. Cognitive Brain Research, 13: 393-405

7. Lockwood, A.H., Salvi, R.J., Coad, M.L., Towsley, M.L., Wack, D.S., Murphy, B.W. (1998). The functional neuroanatomy of tinnitus: evidence for limbic system links and neural plasticity. Neurology, 50:114-20