Schizophrenia may involve bad timing.

People diagnosed with schizophrenia display a wide-ranging breakdown of perception and thought. A glitch in the timing of cell responses across broad swaths of brain tissue may help account for these people's fragmented experience of the world, according to a new study.

In the brains of schizophrenia sufferers, electrical activity fails to synchronize with a specific sound frequency as it does in the brains of mentally healthy people, report psychiatrist Robert W. McCarley of Brockton (Mass.) Veterans Affairs Medical Center and his coworkers.

In healthy individuals, widely separated clusters of neurons harmonize their electrical activity to the so-called gamma frequency of around 40 bursts per second. This match may help produce unified perceptions and memories (SN: 2/20/99, p. 122).

Much research on schizophrenia and other severe mental disorders focuses on activity in specific parts of the brain as measured by imaging devices. McCarley's group instead examined the timing of electrical responses across much of the brain's outer layer, or cortex, using electroencephalogram (EEG) sensors placed on the scalp.

The researchers recruited 15 men currently hospitalized for schizophrenia treatment, most of whom had been diagnosed with the disorder around 20 years ago and had received antipsychotic medication ever since. Another 15 men, none of whom had psychiatric disorders or any immediate relatives with a mental ailment, served as controls.

EEG recordings were made in experimental sessions as each volunteer listened through headphones to series of tones with frequencies of either 20, 30, or 40 vibrations per second.

Neural firing quickly became synchronized with each of the three sound frequencies in the control group. In the schizophrenia group, the brain's electrical output aligned itself with the two lower frequencies but took longer to do so than it did in the control group. Even after an extended period, however, the schizophrenia patients' brain activity did not speed up to the gamma frequency.

McCarley and his team report their findings in the November ARCHIVES OF GENERAL PSYCHIATRY.

Earlier studies suggested that the coordination of gamma-frequency neural activity depends on the chemical messenger GABA, which has also been implicated in schizophrenia, they add.

Gamma activity in the brain offers "considerable promise in understanding sensory and perceptual deficits in schizophrenia," remark Michael F. Green and Keith H. Nuechterlein, both psychologists at the University of California, Los Angeles, in a commentary published in the same journal.

Difficulty in establishing this level of neural activity may partly account for visual problems observed in schizophrenia, the UCLA researchers say. For example, when two images are flashed on a computer screen in succession, schizophrenia sufferers have trouble seeing the first image unless the second one appears only after a relatively long interval.