New Research Links Schizophrenia to Auditory Hallucinations

By Madison Calvanese, Cell & Molecular Biology, 2029

Around 80% of people with schizophrenia experience auditory hallucinations. New research from the University of New South Wales suggests that the link between schizophrenia and auditory hallucinations could stem from a schizophrenic brain's misinterpretation of internal dialogue for external speech. Schizophrenia is a chronic psychiatric illness characterized by symptoms such as delusions, hallucinations, disorganized speech and behavior, and cognitive impairment. There is no exact test for schizophrenia and is usually only diagnosed after any other possible conditions have been excluded. However, this new study believes that they have identified certain biological markers to look for when diagnosing schizophrenia–making the diagnosis and treatment processes more efficient.

The theory that auditory hallucinations could stem from an inner voice in a person’s head being misinterpreted as external speech has been suggested but left unproven for many years. Inner speech is what many people know as ‘the voice in your head.’ It narrates thoughts, feelings, and actions; sometimes without a person even noticing that it's happening. Research shows that when a person speaks in their own head or out loud, the part of the brain that processes outside sounds becomes less active–anticipating the sound of a person’s own voice. In contrast, a schizophrenia brain will react as if the inner voice is coming from someone else.

This phenomenon has been studied using an EEG, a machine that measures electrical brain activity. When a healthy person speaks in their own head or out loud, the electrical activity in their head decreases–suppressing signals in the auditory cortex, the part of the brain that processes sound and helps people distinguish their own speech from external noise. However, when a schizophrenic person experiences inner dialogue, the electrical activity in their brain increases, creating a dysfunction in signalling between the auditory cortex and other parts of the brain. As a result, the brain interprets the inner voice as coming from someone else. This process explains why auditory hallucinations feel so real to patients. The words are technically being spoken by a person. Only, the person is themselves and the speech is in their own mind.

This new information may be beneficial in early diagnosis and treatment of schizophrenia. If these symptoms in brain electrical activity can be determined before onset of auditory hallucinations, patients could receive early treatment. Additionally, this test could lead to a better understanding of the biological causes and symptoms of schizophrenia, leading to more specific and specialized treatments.