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BioMed Research International
Volume 2014, Article ID 906104, 9 pages
http://dx.doi.org/10.1155/2014/906104
Research Article

Abnormal Early Gamma Responses to Emotional Faces Differentiate Unipolar from Bipolar Disorder Patients

1Institute of Brain Science, School of Medicine, National Yang-Ming University, Taipei 112, Taiwan
2Integrated Brain Research Unit, Division of Clinical Research, Department of Medical Research, Taipei Veterans General Hospital, Taipei 112, Taiwan
3Department of Computer Science, National Chiao Tung University, Hsinchu 300, Taiwan
4Department of Psychiatry, Taipei Veterans General Hospital, Taipei 112, Taiwan
5Division of Psychiatry, School of Medicine, National Yang-Ming University, Taipei 112, Taiwan

Received 15 October 2013; Revised 30 January 2014; Accepted 1 February 2014; Published 13 March 2014

Academic Editor: Yong He

Copyright © 2014 T. Y. Liu et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

This study investigates the cortical abnormalities of early emotion perception in patients with major depressive disorder (MDD) and bipolar disorder (BD) using gamma oscillations. Twenty-three MDD patients, twenty-five BD patients, and twenty-four normal controls were enrolled and their event-related magnetoencephalographic responses were recorded during implicit emotional tasks. Our results demonstrated abnormal gamma activity within 100 ms in the emotion-related regions (amygdala, orbitofrontal (OFC) cortex, anterior insula (AI), and superior temporal pole) in the MDD patients, suggesting that these patients may have dysfunctions or negativity biases in perceptual binding of emotional features at very early stage. Decreased left superior medial frontal cortex (smFC) responses to happy faces in the MDD patients were correlated with their serious level of depression symptoms, indicating that decreased smFC activity perhaps underlies irregular positive emotion processing in depressed patients. In the BD patients, we showed abnormal activation in visual regions (inferior/middle occipital and middle temporal cortices) which responded to emotional faces within 100 ms, supporting that the BD patients may hyperactively respond to emotional features in perceptual binding. The discriminant function of gamma activation in the left smFC, right medial OFC, right AI/inferior OFC, and the right precentral cortex accurately classified 89.6% of patients as unipolar/bipolar disorders.