Auditory hallucinations or hearing voices affects patients with schizophrenia and mood disorders. What's it like and what causes auditory hallucinations.
You are in a crowd when you hear your name. You turn, looking for the speaker. No one meets your gaze. It dawns on you that the voice you heard must have sprung from your own mind.
This foray into the uncanny is as close as most people come to experiencing auditory hallucinations or "hearing voices," a condition that affects 70% of patients with schizophrenia and 15% of patients with mood disorders such as mania or depression. For these individuals, instead of hearing just one's name, voices produce a stream of speech, often vulgar or derogatory ("You are a fat whore," "Go to hell") or a running commentary on one's most private thoughts.
The compelling aura of reality about these experiences often produces distress and disrupts thought and behavior. The sound of the voice is sometimes that of a family member or someone from one's past, or is like that of no known person but has distinct and immediately recognizable features (say, a deep, growling voice). Often certain actual external sounds, such as fans or running water, become transformed into perceived speech.
One patient described the recurrence of voices as akin to being "in a constant state of mental rape." In the worst cases, voices command the listener to undertake destructive acts such as suicide or assault. But hearing voices is not necessarily a sign of mental illness, so understanding the mechanics of auditory hallucinations is crucial to understanding schizophrenia and related disorders.
For example, your occasional illusionary perception of your name spoken in a crowd occurs because this utterance is uniquely important. Our brains are primed to register such events; so on rare occasions the brain makes a mistake and reconstructs unrelated sounds (such as people talking indistinctly) into a false perception of the spoken name.
Hallucinated voices are also known to occur during states of religious or creative inspiration. Joan of Arc described hearing the voices of saints telling her to free her country from the English. Rainer Maria Rilke heard the voice of a "terrible angel" amidst the sound of a crashing sea after living alone in a castle for two months. This experience prompted his writing the Duino Elegies.
Causes of Auditory Hallucinations
How can we understand differences between an inspired voice, an isolated instance of hearing one's own name, and the voices of the mentally ill? One answer is that "non-pathological" voices occur rarely or perhaps only once. Not so for the person with mental illness. Without treatment, these experiences recur relentlessly.
Brain imaging studies have found that parts of the temporal lobe activate during these hallucinations. Our research at Yale University, as well as studies conducted at the Institute of Psychiatry in London, also detected activation in an area of the brain known as Broca's region during production of "inner speech" or verbal thought.
One theory is that voices arise because Broca's area "dumps" language outputs into parts of the brain that ordinarily receive speech inputs from the outside. To test this theory we are using trans-cranial magnetic stimulation (TMS) to reduce the excitability of portions of the temporal lobe and Broca's region.
So far, most patients appear to experience significant improvements from TMS directed to both brain regions, with improvements lasting from two months to over a year. These results, although preliminary, suggest an alternative treatment if validated in larger-scale studies.
What remains unaddressed is the root cause of abnormal brain activations. We are pursuing three intertwined ideas. The first is based on studies suggesting that schizophrenia patients suffer from reduced brain connectivity. (See also Impact of Schizophrenia on the Brain.) As a result, certain groups of neurons, such as those responsible for producing and perceiving language, may begin to function autonomously, beyond the control or influence of other brain systems. It is as if the string section of the orchestra suddenly decided to play its own music, disregarding everyone else.
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The second idea is that deprivation of social interaction - namely human conversation-makes the brain more likely to produce hallucinated conversations. Often one of the first signs of schizophrenia-occurring well before manifestations such as hearing voices-is social isolation.
Indeed, sensory deprivation can produce hallucinations in the sense mode that is deprived. An example is Charles Bonnet Syndrome, where visual impairments in the elderly can produce visions of human figures. Could the absence of actual spoken human conversation-a cornerstone of day-to-day human intellect and creativity-produce hallucinated conversations? Recall the extreme isolation that preceded the appearance of Rilke's startling voice.
Third, heightened emotions may play a role in producing voices. Indeed, heightened emotionality prompts the brain to produce information consonant with that emotional state. For example, a low mood favors generation of thoughts that are themselves depressing. It is possible that intense states of emotion could pre-select and perhaps elicit from the brain certain verbal messages having the same emotional charge.
Verbal messages expressed by voices often are highly emotional. Moreover, when schizophrenia begins, these persons are often in states of extreme fear or elation. It could be that these powerful emotional states increase the propensity of the brain to produce corresponding verbal "messages."
This would account for the fact that voices also emerge during states of extreme, but incidental, emotionality brought on by inspired thought, mania, depression, or ingestion of certain drugs. Here the voices disappear when the emotional states return to normal. The brains of schizophrenia sufferers may be vulnerable to becoming "stuck" in these hallucinatory states.
Our hypothesis is that voices arise from different combinations of these three factors-reduced brain integration, social isolation, and high levels of emotionality. This view has become the focus of efforts to understand and help patients with mental illness quiet their minds.