Auditory hallucinations are likely the result of abnormalities in two brain processes: a “broken” corollary discharge that fails to suppress self-generated sounds, and a “noisy” efference copy that makes the brain hear these sounds more intensely than it should. That is the conclusion of a new study published October 3 rd in the open-access journal PLOS Biology by Xing Tian, of New York University Shanghai, China, and colleagues.
Patients with certain mental disorders, including schizophrenia, often hear voices in the absence of sound. Patients may fail to distinguish between their own thoughts and external voices, resulting in a reduced ability to recognize thoughts as self-generated. In the new study, researchers carried out electroencephalogram (EEG) experiments measuring the brain waves of twenty patients diagnosed with schizophrenia with auditory hallucinations and twenty patients diagnosed with schizophrenia who had never experienced such hallucinations.
In general, when people are preparing to speak, their brains send a signal known as “corollary discharge” that suppresses the sound of their own voice. However, the new study showed that when patients with auditory hallucinations were preparing to speak a syllable, their brains not only failed to suppress these internal sounds, but had an enhanced “efference copy” response to internal sounds other than the planned syllable.
The authors conclude that impairments in these two processes likely contribute to auditory hallucinations and that targeting them in the future could lead to new treatments for such hallucinations.
The authors add, “People who suffer from auditory hallucinations can ‘hear’ sounds without external stimuli. A new study suggests that impaired functional connections between motor and auditory systems in the brain mediate the loss of ability to distinguish fancy from reality.”
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In your coverage, please use this URL to provide access to the freely available paper in PLOS Biology : http://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.3002836
Citation: Yang F, Zhu H, Cao X, Li H, Fang X, Yu L, et al. (2024) Impaired motor-to-sensory transformation mediates auditory hallucinations. PLoS Biol 22(9): e3002836. https://doi.org/10.1371/journal.pbio.3002836
Author Countries : China
Funding: This study was supported by the National Natural Science Foundation of China 32071099 and 32271101 ( https://www.nsfc.gov.cn/ ), Natural Science Foundation of Shanghai 20ZR1472100 ( https://svc.stcsm.sh.gov.cn/ ), Program of Introducing Talents of Discipline to Universities, Base B16018 to X.T., East China Normal University (ECNU) Academic Innovation Promotion Program for Excellent Doctoral Students YBNLTS2019-026 ( http://www.yjsy.ecnu.edu.cn/ ) and China Postdoctoral Foundation under Grant Number 2024M752047 ( https://www.chinapostdoctor.org.cn/bshjjh/ ) to F.Y. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
PLOS Biology
Experimental study
People
Competing interests: The authors have declared that no competing interests exist.