Brain Signal Function Might Hold Clue to Understanding Schizophrenia

What causes the mental dissociations of schizophrenia, and how can we aid schizophrenics in controlling their condition? These are questions that have long interested researchers who study brain functions and the mind. Now, Rice University assistant professor of psychology Geoffrey Potts, who has been monitoring brain wave activity in schizophrenic patients, may have found a clue.

“Schizophrenia means ‘split mind,’” Potts says, “but it’s a misconception to think that means two people in one head. Split mind refers to a functional disconnection between parts of an individual’s mind. Whatever process that allows the different portions of the brain to communicate efficiently with each other is disrupted in patients with schizophrenia.”

One measure of the communication between different portions of the brain is brain-wave signals known as “event-related potentials” (ERPs). The ERP signal Potts is interested in reflects communication between the frontal lobe, which controls functions like planning, organization, and motivation and knows what tools and information are relevant to a task or goal, and the visual areas in the back of the brain, which detect objects that the eye sees. Within two-tenths to three-tenths of a second, communication between these areas alerts the brain about whether something the eye sees is needed for a task at hand. A disruption of this signal, however, could be a hallmark of schizophrenia.

Potts initially attempted to measure ERP responses to auditory stimulation and found the signal was absent. However, schizophrenia impairs the auditory system, so he recognized the possibility that the apparent loss of ERP might be because the brain was not processing the auditory stimuli. So he devised a second study using visual stimuli.

In this study, Potts measured ERPs in 14 schizophrenic patients and 14 control subjects at Harvard Medical School. Subjects, wearing a hair-net-like cap wired with 64 electrodes to monitor their brain waves, sat in front of a computer and pressed selected keys when certain symbols appeared on the monitor. The participants had to distinguish between different symbols as well as the symbols’ locations, such as at the top or bottom corner of the monitor. Ideally, when the visual areas of the brain detect a symbol on the monitor, that information is communicated to the frontal lobes to determine whether that symbol is relevant, prompting the participant to press the appropriate key on the keyboard.

Potts observed that the size of ERPs in schizophrenic patients was 80 to 95 percent smaller than those measured in the control group, indicating that patients with schizophrenia have problems in the part of the brain that decides whether something is important for a task, not simply in perceiving things properly. Potts says his finding might account for the attention deficits that occur in many schizophrenics.

Potts is now collaborating with researchers at Baylor College of Medicine and the Houston Veterans Affairs Medical Center to measure a combination of visual and auditory signals in schizophrenic patients. “If we better understand the specific neural systems that are impacted by schizophrenia,” he says, “we might be able to develop drugs that target those areas and leave the neural systems that are working fine alone. This would improve the effectiveness of the drugs and reduce side effects.”

Potts’s research is funded by the National Alliance for Research on Schizophrenia and Depression, and his study was published in the May issue of the Archives of General Psychiatry. Co-authors of the paper were Brian O’Donnell, now at the University of Indiana, Bloomington; Yoshio Hirayasu, now at Kyorin University School of Medicine, Tokyo; and Robert McCarley at Harvard Medical School, Boston, and Brockton Veterans Affairs Medical Center, Brockton, Massachusetts.

—B. J. Almond