Reduced auditory evoked gamma band response and cognitive processing deficits in first episode schizophrenia

Abstract

Objectives. Gamma-band oscillations (e.g., the early auditory evoked gamma-band response, aeGBR) have been suggested to mediate cognitive and perceptual processes by driving the synchronization of local neuronal populations. Reduced aeGBR is a consistent finding in patients with schizophrenia and high-risk subjects, and has been proposed to represent an endophenotype for the illness. However, it is still unclear whether this reduction represents a deficit in sensory or cognitive processes, or a combination of the two. The present study investigated this question by manipulating the difficulty of an auditory reaction task in patients with first-episode schizophrenia and healthy controls. Methods. A 64-channel EEG was recorded in 23 patients with first-episode schizophrenia and 22 healthy controls during two conditions of an auditory reaction task: an easy condition that merely required low-level vigilance, and a difficult condition that placed significant demands on attention and working memory. Results. In contrast to healthy controls, patients failed to increase aeGBR power and phase-locking in the difficult condition. In patients, aeGBR power and phase-locking indices were associated with working memory deficits. Conclusions. The observed results confirm the applicability of aeGBR disturbances as a stable endophenotype of schizophrenia, and suggest a cognitive, rather than sensory, deficit at their origin.

Key words::

• schizophrenia
• EEG
• gamma
• first episode
• auditory

Acknowledgments

Parts of this work were prepared in the context of Clarissa Lanig's dissertation at the Faculty of Medicine, Universität Hamburg, Hamburg. This work has been supported by DFG, SFB 936 “Multi-Site Communication in the Brain”, project C6.

Statement of Interest

None to declare.

Supplementary material available online

Supplementary Figure 1. Scalp topographies of the aeGBR.