Imagine waking up one morning to the sound of music playing on the radio, only to find that the radio is not on. Or, imagine sitting on an aeroplane, listening to the low hum of the engine, when the sound starts to transform into musical patterns, which follow you even after you’ve left the plane. Imagine that every time you lay down, you hear your friends and family singing Happy Birthday as if they were really there.
Hallucinations can occur across any of our sense modalities (Kumar et al., 2014), and while most people are aware of the concept of hearing voices that are not really there, the musical hallucination is a less familiar phenomenon. The above examples are real descriptions of musical hallucinations given by neurologist Oliver Sacks (2008) in his book Musicophilia, which demonstrate the defining characteristics of a musical hallucination: the perception of music, out with the control of the sufferer, that has no physical basis in the environment (Sacks, 2008). Importantly though, most musical hallucinations are not accompanied by psychosis (Kumar et al., 2014), and sufferers quickly become aware that their hallucinations are a product of their mind.
History and causes
Historical cases of auditory and musical hallucinations have been recorded since the early 19th century (Berrios, 1990), and may be an auditory form of a condition known as Charles Bonnet Syndrome (Evers & Ellger, 2004); a condition in which people who are blind, or partly blind, experience visual hallucinations. Charles Bonnet Syndrome is considered a deafferentation problem, in that a lack of input to nerves that normally receive visual information causes neuronal hyperactivity, resulting in hallucinations (Sacks, 2008). Musical Hallucinations resulting from hearing loss (which is the most common type of hallucination (Kumar et al., 2014)) are thought to have a similar cause (Vanneste, Song & De Ridder, 2013). You can hear Oliver Sacks talking about Charles Bonnet Syndrome here: https://www.youtube.com/watch?v=SgOTaXhbqPQ
Other common causes of musical hallucinations are brain tumours or disease, stroke, epilepsy and sometimes psychosis. Hallucinating patients with hearing loss usually experience a gradual onset which often starts with humming sounds or tinnitus, and gradually develops into a complex musical experience. (Berrios, 1990)
Studying Musical Hallucinations in the brain
Exploring what happens in the brain during a musical hallucination has not been an easy task, because hallucinations are difficult to manipulate, and occur rarely in the population. Between-subjects experiments can be tricky because there are a wide variety of types of hallucination, and the condition is often co-morbid with other disorders. This makes it difficult to pin down brain activity that is associated with only the hallucination. On the other hand, observing the brain activity of only one hallucinating patient has been difficult because the patient cannot control their hallucinations, so it has not been possible to compare brain activity when hallucinating, to brain activity when not hallucinating. (Kumar et al., 2014 )
In response to this problem, Kumar et. al (2014) developed an innovative new experiment design, that utilised a technique called residual inhibition (RI); an approach that has been used before in tinnitus studies. The idea behind RI is that a sound which masks the hallucination (or tinnitus) is played, and for a few seconds after the masking sound ends, the hallucination is reduced. Researchers can then compare the brain activity during this reduced period, to brain activity when the hallucination has returned to its usual state. This RI process doesn’t work with all patients, but fortunately the study only required one.
Where and how in the brain musical hallucinations take place is not precisely known (Evers & Ellger, 2004), as different neuroimaging studies have not yielded consistent results (Kumar et al., 2014). However, Vanneste et al. (2013) proposed that musical hallucinations have a similar underlying mechanism to tinnitus, known as thalamocortical dysrhythmia. This model involves the deafferentation idea described above, and is centred round the theory that when there is a lack of stimulation from the environment to the ear, hyperactivity in the brain occurs. In support of this model Vannetse et al. (2013) and Kumar et al. (2014) found that musical hallucinations seemed to share some neural bases with tinnitus, in increased gamma and theta band activity in auditory areas of the brain.
Additionally, Kumar et al. (2014) propose a new model to explain musical halluciantions. The model is based on the idea of “predictive coding” in the brain, which says that higher level areas in the brain send predictions to lower level areas about what is happening in the environment (these messages are observed as gamma activity), while lower areas send corrections back to these higher areas (observed as beta activity). In this way our perception of the environment is formed. However, when there is a lack of input from the ear, due to hearing loss, problems arise in this system and the top down prediction messages give rise to musical hallucinations (Kumar et al., 2014).
Effectiveness of different treatments for musical hallucinations vary, and are usually aimed at treating the underlying cause of the hallucination rather than the hallucination itself. For example, treating the brain disease, tumour or hearing loss. For many people, there is no effective cure, although for some people increasing audio stimuli can help, and some anti-epileptic or anti-depression drugs have been effective (Evers & Ellger, 2004). In some cases, hallucinations also disappear on their own (Coebergh et al., 2015), and not all musical hallucinations are experienced as unpleasant. Composers who are thought to have experienced and derived inspiration from musical hallucinations include Haydn, Ravel, Donizetti, and Smetana (Evers & Ellger, 2004: Sacks, 2008), and Schumann is rumoured to have used his musical hallucinations in the composition of his violin concerto in D minor
The discovery that some types of hallucination can occur without the detachment from reality associated with psychosis, has been an important one, and it is still thought that these types of hallucination are underreported due to a fear of being labelled insane (Evers & Ellger, 2004; Yacoub & Ferrucci, 2011). We still have a lot to learn about musical hallucinations, and research in this area is a useful way of learning more about the mysteries of the brain. Furthermore, a closer look at the neural bases of these kinds of ‘organic’ hallucinations, is a reminder that our perception of the world is not totally dependent on physical factors in the environment, but comes partly from the creations or ‘predictions’ of our brains. Seeing and hearing might not be believing, but if a musical hallucination was responsible for Schumann’s violin concerto then the human brain might be even more fascinating than we thought.
Berrios, G. E. (1990). Musical hallucinations. A historical and clinical study. The British Journal of Psychiatry, 156(2), 188-194.
Coebergh, J. A. F., Lauw, R. F., Bots, R., Sommer, I. E. C., & Blom, J. D. (2015). Musical hallucinations: review of treatment effects. Frontiers in Psychology, 6, 814. Retrieved from: http://doi.org/10.3389/fpsyg.2015.00814
Evers, S., & Ellger, T. (2004). The clinical spectrum of musical hallucinations. Journal of the neurological sciences, 227(1), 55-65.
Kumar, S., Sedley, W., Barnes, G. R., Teki, S., Friston, K. J., & Griffiths, T. D. (2014). A brain basis for musical hallucinations. Cortex, 52, 86-97.
Sacks, O. (2008). Musicophilia: Tales of music and the brain. London. Picador
Vanneste, S., Song, J. J., & De Ridder, D. (2013). Tinnitus and musical hallucinosis: the same but more. Neuroimage, 82, 373-383.
Vitorovic, D., & Biller, J. (2013). Musical hallucinations and forgotten tunes–case report and brief literature review. Frontiers in Neurology, 4, 109. Retrieved from: http://journal.frontiersin.org/article/10.3389/fneur.2013.00109/full
Yacoub, R., & Ferrucci, S. (2011). Charles bonnet syndrome. Optometry-Journal of the American Optometric Association, 82(7), 421-427.