Why do people with schizophrenia hear voices?

Chinese researchers investigated what happens in the brain during auditory hallucinations.

About one percent of Austria's population suffers from schizophrenia. Psychiatrists who first introduced the disease in the twentieth century considered it a “splitting of the soul.” Today, science distinguishes a whole range of disorder patterns and manifestations of a complex clinical picture. Schizophrenia usually develops in early adulthood in those affected and tends to develop earlier in men than in women. The individual suffering and social stigma of those affected are great. Typical symptoms include social isolation and expressing loud and compulsive thoughts or fantasies. Many patients also hear voices.

In a new study, a group of researchers led by Xing Tian of New York University in Shanghai investigated the question of what happens in the brains of schizophrenia patients when such audio hallucinations occur (Plos Biology, Oct. 3). According to the authors, those affected often have difficulty distinguishing their thoughts and voices from external noise. Many people view their inner voice as a foreign voice. This reduces the ability to recognize thoughts as products of one's mind. To get to the bottom of the matter, the researchers measured the brain waves of two groups of schizophrenia patients, one with auditory hallucinations and one without. In two cases, test subjects were faced with an unprepared and prepared conversational situation in which they had to pronounce a particular syllable.

The results showed that both groups in the experiment, compared to healthy people, had abnormalities in brain functions that usually suppress a person's voice when speaking. However, this disorder is more serious in patients with schizophrenia who hear voices. Because their responses to sounds are poorly processed, the brain amplifies false or unexpected sounds. Blocking the brain's natural stimulation works in the exact opposite way than intended.

The conclusion the authors draw from this is that if connections between the brain's cognitive and motor systems are damaged, this leads to a “loss of the ability to distinguish between fantasy and reality.”