Gregory Light, PhD

By Brenda L. Mooney

SAN DIEGO--A deficiency in the neural processing of simple auditory tones helps explain some of the clinical symptoms associated with schizophrenia, such as missing social cues or hearing voices others cannot hear, according to a new study from the San Diego VA Healthcare System and the University of California San Diego.

The processing problems can cascade across wide swaths of the brain in schizophrenia patients, according to the study in the current online edition of the journal Neuroimage.

Auditory hallucinations and unfounded suspicious ideas are common in schizophrenia, which affects about 1% of the U.S. population and often is diagnosed in young adults, the same age many recruits join the military.

"Impairments in the early stages of sensory information processing are associated with a constellation of abnormalities in schizophrenia patients," said senior author Gregory Light, PhD, associate director of the VISN-22 Mental Illness, Research, Education and Clinical Center (MIRECC) at the San Diego VAMC.

Light suggested that impairments of neural processing of simple auditory tones could explain how schizophrenia patients develop clinical symptoms such as hearing voices that others cannot hear and difficulty with cognitive tasks involving attention, learning and recalling information.  "If someone's brain is unable to efficiently detect subtle changes in sounds despite normal hearing, they may not be able to automatically direct their attention and rapidly encode new information as it is being presented.”

For the study, researchers employed electroencephalography – a technique that records patterns of electrical brain activity using electrodes positioned on the scalp – on 410 schizophrenia patients and 247 members of a control group without psychiatric symptoms. They found that in healthy volunteers, a specific pattern of EEG responses across a complex network of brain structures occurs almost immediately in response to changes in auditory tones. In patients with schizophrenia, however, the researchers found that this normal process is disrupted. In fact, reduced activity in specific areas of the medial frontal lobe quickly propagated to other regions of the brain that support activation of attentional networks.

"Changes in the tone of speech convey complex information including nuances of emotional meaning and content," said Light, who also is an associate professor at UC San Diego. "If a patient's brain is not processing auditory information optimally, he or she may miss out on important-but-subtle social cues and other critical information. They may not properly recognize sarcasm or humor that is carried by pitch changes in speech. This can be a major barrier to achieving better functioning in social relationships, school or job performance, and ultimately limit their overall quality of life."

The study “makes a valuable contribution to our understanding of how impairments in the very early processing of sensory information in schizophrenia can explain the complex symptoms of the illness. This new knowledge may also be useful in developing better pharmacological and non-pharmacological treatments for schizophrenia,” added Stephen R. Marder, MD, VISN-22 MIRECC director and a professor at UCLA's Semel Institute for Neuroscience and Human Behavior.