Findings published in npj Schizophrenia have shed light on the brain mechanisms associated with auditory hallucinations among patients with schizophrenia. Primarily, altered tonotopic organization of the auditory cortex plays a prominent role in this phenomenon, and alteration may occur during infancy, researchers reported.
“A prevailing view of auditory hallucinations is that they represent abnormalities in language production,” Sophia Frangou, MD, PhD, professor of psychiatry at Icahn School of Medicine at Mount Sinai, told Healio Psychiatry. “This study turns this argument on its head, as it links vulnerability to auditory hallucinations to a deviation in the organization of the auditory cortex, which is the part of the brain that processes sound. Further, this deviation seems to be established early in development, before the emergence of language abilities.”
Frangou and colleagues noted that auditory hallucinations affect more than 80% of patients with schizophrenia and pose a significant danger to patients, as they often increase the risk for aggressive or suicidal behavior. The researchers sought to determine whether these hallucinations arise because of abnormalities in primary sensory processing or from failures of higher-order functions. To do so, they used an ultra-high field scanner with a high-strength magnet to obtain high-resolution images of brain activity while participants in their study listened to a range of very low to very high frequencies. They noted that healthy brains process these frequencies in an organized fashion, with each frequency activating a specific part of the auditory cortex to form a tonotopic map.
Frangou and colleagues obtained tonotopic maps from 16 patients with schizophrenia and a history of recurrent auditory hallucination (mean age, 29.6 years; 75% men), as well as 22 healthy participants (mean age, 29.3 years; 59% men). Patients with schizophrenia exhibited abnormally increased activation and altered tonotopic organization of the auditory cortex while listening to the tones — an activity the researchers described as “a purely perceptual task.”
Because the brain abnormalities associated with auditory hallucinations may be established by infancy, the researchers concluded that organization of the auditory cortex “may serve as a biomarker” to identify vulnerable individuals at an early age.
“Despite the exponential increase in neuroimaging capabilities in recent years, the brain origins of most psychiatric symptoms are still unclear,” Frangou said. “This study provides a direct link between a specific symptom — auditory hallucinations — and a specific brain region located in the auditory cortex. We are excited about the possibility of testing for the propensity for auditory hallucinations in people at high risk for schizophrenia years before symptoms may arise.” – by Joe Gramigna
Disclosures: Frangou reports no relevant financial disclosures. Please see the study for all other authors’ relevant financial disclosures.