a marching bandHave you ever been so sure you were hearing a sound, only to check the supposed source and find that there was no noise at all? Musical hallucinations are a real phenomenon and can affect people so strongly that they are convinced there is an entire marching band in the next room. New research from Newcastle University documented the brain activity of one woman who experiences vivid musical hallucinations. By comparing the subject’s brain activity during the highs and lows of musical hallucinations, the research team was able to learn more about how the brain processes music and interprets its surroundings.

Sylvia, who experiences auditory hallucinations, was invited by the researchers to participate in a study on the condition. They first examined the process of soothing the music in Sylvia’s mind. Sylvia told the researchers that listening to real music—to Bach specifically—sometimes calms the auditory hallucinations. Their first test was measuring how long her mind was quiet after tuning in to Bach. Immediately after listening, she had several seconds without hallucinations, but then the mental music returned, reaching a crescendo after a minute and a half.

Next, the researchers measured Sylvia’s brain activity during a bout of hallucinations. Wearing headphones, Sylvia situated her head inside a scanner that measures the brain’s magnetic field. The researchers piped Bach into her headphones for 30 second intervals. Once the music stopped, Sylvia used a keyboard to rate the strength of her hallucinations, which allowed the research team to compare her brain activity at their strongest and weakest points.

The findings support a theory proposed by Dr. Karl Friston, one of the study’s co-authors, which states that the brain is in the business of telling the future. When the brain hears sounds, it attempts to generate a pattern so it can anticipate the next piece of input. Brains love pattern-recognition, so music, which follows certain structures, is particularly alluring for the brain’s predictive engines.

Many people who experience auditory hallucinations also suffer from some level of hearing loss; Sylvia has been wearing hearing aids for 20 years. Since hearing loss results in less auditory input, the brain goes into overdrive, making stronger predictions and eventually reaching the point where the predictions seem totally real.

This research, though limited to one person, is an important step in understanding not only musical hallucinations, but also how the brain makes sense of its surroundings.

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