This article is more than 5 years old. Information may no longer be current.

Elevated dopamine may worsen hallucinations in schizophrenia

Elevated dopamine levels could exacerbate auditory hallucinations among patients with schizophrenia, according to researchers.

"Our brain uses prior experiences to generate sensory expectations that help fill in the gaps when sounds or images are distorted or unclear. In individuals with schizophrenia, this process appears to be altered, leading to extreme perceptual distortions, such as hearing voices that are not there,” study author Guillermo Horga, MD, PhD, department of psychiatry, New York State Psychiatric Institute, Columbia University Medical Center, said in a press release.

“Furthermore, while such hallucinations are often successfully treated by antipsychotic drugs that block the neurotransmitter dopamine in a brain structure known as the striatum, the reason for this has been a mystery since this neurotransmitter and brain region are not typically associated with sensory processing,” Horga said.

Horga and colleagues used molecular imaging to examine unmedicated patients with schizophrenia with differing hallucination severities and healthy individuals. They used a novel task to measure illusory changes in the perceived duration of auditory stimuli under different levels of uncertainty in both healthy participants and participants with schizophrenia, according to the press release. Specifically, they assessed how enhancing or rejecting sensory expectations effected the strength of the auditory illusion. They also measured dopamine release before and after administering a drug designed to release dopamine.

Thirty patients completed the study. The results showed that patients who experienced hallucinations appeared to perceive sounds similarly to what they had been cued to expect, even with less reliable sensory expectations, according to the release. The hallucinations were linked to a perceptual bias, indicating that under uncertainty, there was a disproportional gain on expectations. The researchers found that amphetamine can pharmacologically induce this bias, when participants’ tendency to hear what was expected worsened after receiving the dopamine-releasing drug. In addition, this bias was strongly related to striatal dopamine release, and to cortical volume of the dorsal anterior cingulate, which tracks environmental uncertainty, according to the authors.

"All people have some perceptual distortions, but these results suggest that excess dopamine can exacerbate our distorted perceptions," Horga said in the release. "Novel therapies should aim to improve the processing of contextual information by targeting the dopamine system or downstream pathways associated with modulation of perceptual processing, which likely include the dorsal anterior cingulate cortex.” – by Savannah Demko

Disclosures: The authors report no relevant financial disclosures.