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In late 2015, a 48-year-old woman presented herself to the psychiatric emergency service in Bern, Switzerland with several deep, self-inflicted stab-wounds to her chest. Some measured up to 7cm (2.75in) deep.

She told the physicians that she had followed direct orders from God.

It was a strange case, but not completely unusual, according to psychiatrist Sebastian Walther who first met Sarah in hospital and told BBC Future about her case, as she wished to remain anonymous. Walther recalls that she had a demeanour of “distinctly feeling blessed”, and that she heard voices every minute or so, sometimes lasting for hours. To her they were “divine” and “persistently enjoyable”, despite the fact that these voices gave her deadly instructions.

A brain scan revealed something even more surprising, Sarah had a tumour in a very critical place in her brain, disturbing a “sweet spot” of networks important for processing sound.

While most of us can clearly distinguish between outside sounds and our inner thoughts, many people hear voices – with estimates ranging from 5% to as high as 19% of the general population. Some are benign. But some, when coupled with other mental health issues, can be more distressing. These were the kind of voices Sarah heard.

Auditory hallucinations, like those she experienced, show just how fragile our brain’s auditory input can be. Her case provides a window into how our perceptual processes work and how easily they can be confused.

The voices Sarah heard reveal how fragile our perception is (Credit: Getty Images)

The first step in solving the mystery of Sarah’s behaviour involved diving into her past, to investigate how long she had experienced any similar symptoms. An interest in religion was nothing new for her; she had shown spells of fundamentalist religious interest since the age of 13. This would periodically return but it was never long-lasting.

It was first presumed that Sarah had schizophrenia, because of her auditory hallucinations, but she did not fit the classical symptoms. She did not retreat from social contexts or experience low levels of motivation. “This didn’t apply to her, she was kind of special,” says Walther.

 The brain can adapt to the stress of such a tumour over time

When a brain scan revealed her tumour, Walther realised that her brain network has been “disturbed” in a very critical spot, affecting the way she experiences sounds. Walther estimates that the tumour could have been there since adolescence, which was also when her religious interest began.

Once Walther studied her medical history and symptoms, he noted that she had had only four “periods of symptoms” and they were always the same: she would hear divine voices, feel extremely religious, and bond to religious groups. But this interest would disappear as soon as it came on, and she would feel nothing similar for years until the cycle started once more.

The patient heard distressing voices, which she believed to be messages from God (Credit: Getty Images)

Putting these symptoms together with the location of her tumour, Walther and his colleagues say it’s most likely that her delusional hallucinations were a direct result of the tumour, even though her symptoms appeared suddenly several times throughout her life. That’s because her tumour appears to be the type that is extremely slow-growing, with a very gradual increase over a long period of time.  

That her symptoms only periodically appeared can be explained, they say, because the brain can adapt to the stress of such a tumour over time. “Therefore, we think that it is very likely that the tumour has challenged the network periodically for several weeks or months, which is when the patient experienced these symptoms,” says Walther. Further, the lump in her brain was a benign tumour that does not grow invasively or grow out of control (metastasize), as cancerous tumours do. A second brain scan revealed that her tumour was stable, but due to its location, neither surgery nor radiation was possible.

Walther’s startling conclusion, outlined in the journal Frontiers of Psychiatry, was based on previous knowledge that Sarah’s tumour encroached on areas important for hearing sound, while lesions to nearby spots can increase feelings of “self-transcendence” similar to that shown by Sarah.

Her interest in religion clearly played a role in the content of what her voices told her to do. Unusually, this interest itself could also have been a result of the tumour. That’s because it infiltrated the auditory cortex as it leads into the temporal lobe – a brain area that when disturbed, has been linked to increased levels of spiritual interest in temporal lobe epilepsy patients. The tumour in Sarah’s brain also affected other brain areas linked to “strong spirituality”.

The patient experienced several episodes of obsessive religious interest (Credit: Getty Images)

Of course, from one rare case study such as this, it’s difficult to attribute definitively that her tumour caused her to be religious. However, the authors note that other cases have shown that magnetically stimulating nearby areas in the brain also impacts religiousness and spirituality.

The brain has to rely on guesswork to keep our continuous perception going

Although rare, there are similar cases in the medical literature, though none that match Sarah’s case directly. There was one instance when a female experienced “hyper religiosity” as a result of a fatal brain tumour. This 60-year-old woman had no previous interest in religion, it came on suddenly, and she did not hear voices. Alberto Carmona-Bayonas, who studied this patient in Meseguer General University Hospital in Spain, explains that her tumour was located in the right temporal lobe “for which there is an abundance of previous literature on this phenomenology, especially in epileptics”.

He is keen though, to stress the clear difference between pathological cases such as these and “normal people's beliefs and feelings”. Sarah and this patient show something that is already well understood, that the personalities of people with brain tumors can change, sometimes for the better. How they change largely depends on the particular brain area involved.

Sarah's brain tumour disrupted the networks involved for processing sound (Credit: Getty Images)

Sarah’s case though is still surprising. It is unique because her tumour grew so slowly and the symptoms therefore reoccurred. As her tumour changed over time then, her interest in religion grew and waned. And when a particular part of her brain (the thalamus) was disturbed, it resulted in her hearing voices. Although medication reduced these hallucinations, when she came off it, they returned.

To understand how her tumour caused her symptoms, it helps to understand how we all process sound. One neuroscientist looking into it is Kristiina Kompus of the University of Bergen in Norway. She’s trying to solve the mystery of why some people hear an “inner voice” just as if it is a real one.

One of the reasons auditory hallucinations sound so real is because the same pathways in the brain are involved for real and imaginary voices. “So all the brain areas related to speech processing and auditory processing seem to be very intimately involved in generating the experience of hallucinated voices,” says Kompus. 

Hallucinations therefore tell us more about how our perception works. The thalamus – which for Sarah is impaired by her tumour – plays a fundamental and early role in processing what we hear before it is sent to other brain areas to be interpreted. The sensory information we see and hear around us first comes into the thalamus – think of it as a relay station that routes what we see and hear to the necessary cortex for sorting.

People who hear voices often hear their own 'inner speech' out loud (Credit: Getty Images)

This area then has to work hard at putting it together into meaningful information. This is “based on very sparse information that comes across the auditory nerve,” says Kompus. Unfortunately whenever information is noisy, unreliable or doesn’t seem to be right, the brain “has to rely on guesswork to keep our continuous perception going”.

 It is her particular impairment playing tricks with her mind

Sarah’s case highlights that the sensory information that we get from the outside only plays a small part of what we eventually interpret. Instead we often rely on expectations and predictions. If our thalamus is not working as it should, either because it is impaired or is simply physically thinner (as is often the case in individuals with schizophrenia), it’s no wonder that the rest of our auditory processing is affected.

That Sarah’s particular voices were religious could have been a result of her earlier interest in religion, as people who hear voices often hear their own “inner speech” out loud. “Quite often the hallucinations have to do with the themes that are important to one particular individual,” says Kompus. Hearing voices, she explains, is not a by-product of a mental health issue in itself, but negative voices can of course make an individual feel worse. “If ‘someone’ constantly tells you ‘you are worthless, stupid, and to kill yourself’, it’s no wonder that depression and anxiety is going to get worse.” 

While Sarah still has her faith, her distressing voices no longer taunt her. She has learnt to live well with her tumour, holds down a steady job and now knows that if the voices return, it is her particular impairment playing tricks with her mind, and she can now can seek help before acting out on some of the more distressing commands.

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