The tendency to hear ‘voices’ in schizophrenia may start in infancy

In a new study, researchers found the propensity to hear ‘voices’ in schizophrenia may be established by infancy.

The research was reported by a team from The Mount Sinai Hospital.

Some people suffering from severe mental illness, particularly schizophrenia, hear “voices,” known as auditory hallucinations.

This symptom, which afflicts more than 80% of patients, is among the most prevalent and distressing symptoms of schizophrenia.

Patients “hear voices” speaking to them or about them without anyone actually being there.

Auditory hallucinations, which usually begin in adolescence and young adulthood, “sound” very real to patients and can have a devastating impact on their quality of life because the “voices” are typically distressing and distracting, sometimes compelling the sufferer into suicidal or violent actions.

Uncovering the biological origins of auditory hallucinations is essential for reducing their contribution to the disease burden of schizophrenia.

To examine the biological origins of hearing “voices” in patients with schizophrenia, the team used ultra-high-field imaging to compare the auditory cortex of schizophrenic patients with healthy individuals.

They found that schizophrenic patients who experienced auditory hallucinations had an abnormal tonotopic organization of the auditory cortex.

Tonotopy is the ordered representation of sound frequency in the auditory cortex, which is established in utero and infancy and which does not rely on higher-order cognitive operations.

The study findings suggest that the vulnerability to develop “voices” is probably established many years before symptoms begin.

Specifically, the research team used an ultra-high field scanner with a powerful 7 Tesla magnet to obtain high-resolution images of brain activity while study participants listened passively to tones across a range of very low to very high frequencies.

In healthy brains, these sounds are processed in a very organized fashion; each frequency activates a specific part of the auditory cortex forming a tonotopic map.

The team obtained tonotopic maps from 16 patients with schizophrenia with a history of recurrent auditory hallucinations and 22 healthy study participants.

They found that patients showed greater activation in response to most sound frequencies.

Additionally, the mapping of most sound frequencies to parts of the auditory cortex appeared “scrambled” in patients with schizophrenia, suggesting that the normal processes for the organized representation of sound in the brain are disrupted in schizophrenia.

Because the tonotopic map is established when people are still infants and remains stable throughout life, the study findings suggest that the vulnerability to develop “voices” is linked deviance in the organization of the auditory system that occurs during infancy and precedes speech development and the onset of psychotic symptoms by many years.

According to the authors, in addition to helping doctors spot people who are likely to experience hallucinations before the symptoms appear or become severe, the auditory cortex may be an area of consideration for novel neuromodulation methods to help patients who already have symptoms.

The study is published in NPJ Schizophrenia.

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