Scientists for the first time have identified a fault in the brain waves of schizophrenics that may explain their hallucinations and disturbed thinking, according to an article in the November 8th Proceedings of the National Academy of Sciences.

American researchers studied the brain waves of normal controls and patients with schizophrenia as they responded to images. Affected adults showed no electrical activity in the gamma range, 30 to 100 brain waves per second, that healthy brain cells used to exchange information about the environment and form mental impressions.

“The schizophrenics did not show this gamma-band response at all. There was a pretty dramatic difference,” said senior author Robert W. McCarley, MD.

The predominance of different brain wave frequencies, measured in hertz, or cycles per second, indicate different levels and types of mental activities. Delta waves, below 4 hertz, occur during sleep. Alpha waves, 8 to 13 hertz, occur at relaxed, quiet times. Beta waves are the next fastest, occurring when people are actively thinking.

Gamma waves are harder for scientists to detect because of their low amplitude. But McCarley, lead author Kevin M. Spencer, PhD, and colleagues used a method that checks for synchronicity of the wave cycle (that is, high and low points that line up) to capture gamma activity. Successive waves “in phase” mean brain cells are communicating.

The team used electroencephalography to record the brain waves of 20 schizophrenic and 20 normal patients as they looked at either of two images containing video game figures. In one image, the four shapes were arranged to optically suggest a square in the center. The participants had to press a button to show if they perceived the square or not.

Both groups were able to respond within a second, but those with schizophrenia made more errors and took about 200 milliseconds longer to process the images. More significantly, they showed no evidence of gamma activity “phase-locked” to the pressing of the button, which would have indicated that the brain was normally processing the visual perception guiding their response.

“What some of them did show was a response at a lower frequency, outside the gamma band, which may indicate less efficient communication among neurons,” said McCarley. “If the most efficient communication between assemblies of neurons is at 40 hertz, and the schizophrenic brains are using a lower frequency, it’s likely they have defective communication between cell assemblies and brain regions.” He added that the strongest non-gamma activity was shown by patients with the worst schizophrenia symptoms.

Schizophrenia affects about one percent of the population, or 2.2 million Americans. It is the most common psychotic illness in the U.S.

Antipsychotic medications help many patients control symptoms, but often have unwanted side effects. McCarley said drugs that promote a normal gamma response among neurons would likely help the condition. His group is exploring which receptors in the brain are involved. “If you know the neurochemical identity of the neurons and synapses involved in generating gamma activity, you can try to target treatments toward them,” he said.