Gamma oscillations and schizophrenia

In the last 2 decades, it has become apparent that brain regions communicate by coordinating the firing of populations of neurons. When neurons synchronize their firing, their rhythmic input is reflected in the extracellular field potential as brain oscillations. Rhythmic brain activity in animals and humans can be recorded using noninvasive techniques such as electroencephalography (EEG) by placing recording electrodes on the surface of the scalp and, more rarely, intracranially at the surface of a brain region, such as the temporal lobe or hippocampus. Human EEG was developed as early as the 1920s by German psychiatrist Hans Berger and has been in constant use since then. However, in the last 25 years, advances in signal processing and methods for the analysis of EEG spectra have intensified interest in the use of quantitative EEG for research purposes. Additionally, more recently developed magnetoencephalographic (MEG) techniques have shown great potential for measuring weak magnetic fields generated by rhythmic currents in the brain. With these methods, rhythmic activity of various frequencies such as delta (0–4 Hz), theta (4–8 Hz), alpha (8–12 Hz), beta (12–30 Hz) and gamma (30–200 Hz) can be detected. These neural oscillations are correlated with and are believed to play a role in normal cognitive processes including memory, attention, perceptual binding and consciousness.1