Auditory hallucinations may result from issues in two specific brain functions: a malfunctioning ‘corollary discharge’ that doesn’t adequately mute sounds generated by the individual, and an overly active ‘efference copy’ that amplifies the perception of these self-generated sounds more than necessary. This is the finding of a recent study published on October 3rd in the open-access journal PLOS Biology by Xing Tian and colleagues from New York University Shanghai, China.
Auditory hallucinations may stem from problems in two brain functions: a malfunctioning “corollary discharge” that fails to quiet self-produced sounds, and an overly active “efference copy” that makes these sounds seem louder than they actually are. This conclusion comes from a study released on October 3rd in the open-access journal PLOS Biology by Xing Tian from New York University Shanghai, along with a team of researchers.
Individuals with certain mental health conditions, such as schizophrenia, often experience hearing voices when there are none present. They can struggle to differentiate their own inner thoughts from external voices, which diminishes their ability to recognize these thoughts as being self-generated. In this new research, scientists conducted electroencephalogram (EEG) tests on a group of twenty patients with schizophrenia who experienced auditory hallucinations, compared to a separate group of twenty patients with schizophrenia who had never experienced such hallucinations.
Typically, when a person is about to speak, their brain sends a signal called “corollary discharge” that helps mute the sound of their own voice. However, the study found that for patients experiencing auditory hallucinations, when they prepared to say a syllable, their brains didn’t suppress these internal sounds at all. Instead, they showed an increased “efference copy” response to other internal sounds besides the syllable they intended to say.
The researchers suggest that these inadequacies in the two brain processes are likely linked to the experience of auditory hallucinations, and addressing these areas in future treatments may provide new strategies for management.
The researchers note, “Those who experience auditory hallucinations can ‘hear’ sounds even in the absence of external stimuli. Our findings indicate that disrupted functional connections between motor and auditory systems in the brain may lead to difficulties in distinguishing reality from imagination.”
