Gamma Oscillation in Schizophrenia
post-mortem analysis of white matter pathology. 8, 9 Deficits in functional connectivity have been consistently observed in schizophrenia, as shown by reduced interregional correlations of positron emission tomography and functional magnetic resonance imaging signals. Functional connectivity has been reported to affect the prefrontal, temporal, cingulate and parietal cortices in individuals with schizophrenia.    Functional dysconnectivity may result from structural alterations in
... onal integrity, differences in mapping of projections among brain regions or physiological disturbances of neurotransmission. Disruption of neural synchrony and oscillations, for example, could have a marked impact on functional connectivity within and across brain regions. Findings from cellular, local field potential, and electroencephalographic recordings suggest that gamma oscillations (>30 Hz) are important for integration of information within neural circuits. Gamma oscillations in the neural system were first reported in the olfactory nerves of hedgehogs, which in response to olfactory stimulation, produced trains of sinusoidal oscillations in the gamma frequency band. 13 More recently, gamma oscillations have been associated with numerous perceptual and cognitive processes, including attention, 14-17 memory, 18,19 object recognition, 20 word processing, 21,22 and consciousness. 23 Electroencephalography (EEG) and magnetoencephalography (MEG) have shown that schizophrenia is characterized by alterations in synchrony and oscillatory activity in a variety of paradigms, particularly in the gamma range. These disturb-Dysfunctional neural circuitry has been found to be involved in abnormalities of perception and cognition in patients with schizophrenia. Gamma oscillations are essential for integrating information within neural circuits and have therefore been associated with many perceptual and cognitive processes in healthy human subjects and animals. This review presents an overview of the neural basis of gamma oscillations and the abnormalities in the GABAergic interneuronal system thought to be responsible for gamma-range deficits in schizophrenia. We also review studies of gamma activity in sensory and cognitive processes, including auditory steady state response, attention, object representation, and working memory, in animals, healthy humans and patients with schizophrenia.