Research Article: EEG Microstate Analysis in Drug-Naive Patients with Panic Disorder

Date Published: July 29, 2011

Publisher: Public Library of Science

Author(s): Mitsuru Kikuchi, Thomas Koenig, Toshio Munesue, Akira Hanaoka, Werner Strik, Thomas Dierks, Yoshifumi Koshino, Yoshio Minabe, Takeo Yoshikawa.

Abstract: Patients with panic disorder (PD) have a bias to respond to normal stimuli in a fearful way. This may be due to the preactivation of fear-associated networks prior to stimulus perception. Based on EEG, we investigated the difference between patients with PD and normal controls in resting state activity using features of transiently stable brain states (microstates). EEGs from 18 drug-naive patients and 18 healthy controls were analyzed. Microstate analysis showed that one class of microstates (with a right-anterior to left-posterior orientation of the mapped field) displayed longer durations and covered more of the total time in the patients than controls. Another microstate class (with a symmetric, anterior-posterior orientation) was observed less frequently in the patients compared to controls. The observation that selected microstate classes differ between patients with PD and controls suggests that specific brain functions are altered already during resting condition. The altered resting state may be the starting point of the observed dysfunctional processing of phobic stimuli.

Partial Text: Panic disorder (PD) is a common mental disorder [1]–[3], which is thought to involve aberrant cognitive features such as catastrophic misinterpretation of bodily sensations even during the inter-attack conditions [4]. The lifetime prevalence of PD with or without agoraphobia is about 3–4% [5]. PD is associated with other psychiatric disorders [1]–[2] and a high risk of suicidal attempts [6]. Recent studies emphasize the importance of panic syndromes as a significant source of disability in the general population [2], [7]. It has been argued that the pathophysiology of PD results from dysfunctions in neural microcircuits such as fronto-temporo-limbic circuits [8]-[9]. A number of neuroimaging studies have demonstrated aberrant brain activity in these cortical areas not only during panic attacks [10]–[11] but also during resting [12]–[17]. Furthermore, factor analyses of functional connectivity of spontaneous fMRI-BOLD signal fluctuations, which yields so-called resting-state networks [18]–[24] demonstrated aberrant RSNs in patient with anxiety disorders [25]–[28].

The present results indicate that patients with PD show alterations in a specific subset of sub-second brain functional states. This is consistent with the results from RSN studies using fMRI showing that specific aspects of brain resting networks are affected in patients with PD [25]–[28]. These physiological results are in agreement with the clinical observation that in patients with PD only specific aspects of cognition are affected [42]–[44].