New Study Reveals Missing Brain Activity in Schizophrenia Patients Hearing Voices

A recent study has uncovered a crucial area of brain activity that is lacking in individuals with schizophrenia who experience auditory hallucinations.

According to the analysis of brain wave data, a combination of two neurological functions may be responsible for triggering auditory verbal hallucinations in these individuals.

Researchers from China have identified a breakdown in the brain’s ability to prepare the senses for specific words to be spoken. However, this impairment alone is not sufficient to cause hallucinations. Another area responsible for filtering the brain’s internal chatter is also found to be heightened in individuals with schizophrenia who hear voices.

Without the suppression of self-generated sounds along with the increased internal noise-associated signals, the individual’s mental processes can become disorganized and confusing.

The research team explains, “People experiencing auditory hallucinations can perceive sounds without any external stimuli. Impaired functional connections between the motor and auditory systems in the brain contribute to the inability to distinguish between imagination and reality.”

Neuroscientist Fuyin Yang and colleagues from Shanghai Jiao Tong University School of Medicine conducted brain scans on 20 patients diagnosed with schizophrenia who reported auditory hallucinations. They compared these scans to those of another 20 schizophrenia patients who did not experience hallucinations. Both groups of patients were stable and were receiving antipsychotic medication during the study. A control group of individuals without schizophrenia was also included for comparison.

Analysis of electroencephalogram (EEG) data from the three groups of patients, who were asked to hear and then speak a short syllable, revealed significant differences in brain activity.

Both groups of schizophrenia patients exhibited reduced activity related to the brain’s ability to predict the sound of their own voice before speaking, known as corollary discharge. This function allows the brain to anticipate self-produced sounds and distinguish them from external stimuli.

Interestingly, only the patients reporting auditory hallucinations showed hyperactivity in efference copy – the motor signal that guides speech production and is described as an internal auditory representation.

In individuals without hallucinations and schizophrenia patients without auditory experiences, this signal was only heightened when preparing to speak a specific syllable. However, in those hearing voices, the enhancement was more generalized, leading to increased internal brain activity.

The researchers suggest that the imprecise activation of efference copy results in the varied enhancement and sensitization of the auditory cortex, ultimately causing auditory hallucinations.

By understanding the mechanisms behind these hallucinations, researchers hope to develop more effective treatments for individuals with schizophrenia.

The findings of this study were published in PLOS Biology.