Increased Intrinsic Connectivity of the Default Mode Network in Temporal Lobe Epilepsy: Evidence from Resting-State MEG Recordings.

Fu-Jung Hsiao,Yung-Yang Lin,Chun-Hing Yiu,Yang-Hsin Shih,Der-Jen Yen,Wei-Ta Chen,Chien Chen,Shang-Yeong Kwan,Hsiang-Yu Yu,Kewei Chen

doi:10.1371/journal.pone.0128787

Fu-Jung Hsiao, Yung-Yang Lin + Show 8 more

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https://doi.org/10.1371/journal.pone.0128787

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Abstract

The electrophysiological signature of resting state oscillatory functional connectivity within the default mode network (DMN) during spike-free periods in temporal lobe epilepsy (TLE) remains unclear. Using magnetoencephalographic (MEG) recordings, this study investigated how the connectivity within the DMN was altered in TLE, and we examined the effect of lateralized TLE on functional connectivity. Sixteen medically intractable TLE patients and 22 controls participated in this study. Whole-scalp 306-channel MEG epochs without interictal spikes generated from both MEG and EEG data were analyzed using a minimum norm estimate (MNE) and source-based imaginary coherence analysis. With this processing, we obtained the cortical activation and functional connectivity within the DMN. The functional connectivity was increased between DMN and the right medial temporal (MT) region at the delta band and between DMN and the bilateral anterior cingulate cortex (ACC) regions at the theta band. The functional change was associated with the lateralization of TLE. The right TLE showed enhanced DMN connectivity with the right MT while the left TLE demonstrated increased DMN connectivity with the bilateral MT. There was no lateralization effect of TLE upon the DMN connectivity with ACC. These findings suggest that the resting-state functional connectivity within the DMN is reinforced in temporal lobe epilepsy during spike-free periods. Future studies are needed to examine if the altered functional connectivity can be used as a biomarker for treatment responses, cognitive dysfunction and prognosis in patients with TLE.

Highlights

Temporal lobe epilepsy (TLE) is the most common type of focal symptomatic or cryptogenic epilepsies, and it is characterized by recurrent, unprovoked seizures originating from the medial or lateral temporal lobe
A significantly larger mean Imaginary coherence (IC) value was found in the right medial temporal (MT) in TLE patients when compared with control subjects
In the theta band, the mean IC value was significantly larger in the bilateral anterior cingulate cortex (ACC) of TLE patients when compared with control subjects

Summary

Introduction

Temporal lobe epilepsy (TLE) is the most common type of focal symptomatic or cryptogenic epilepsies, and it is characterized by recurrent, unprovoked seizures originating from the medial or lateral temporal lobe. TLE is associated with various cognitive dysfunctions, including intellectual, language, visuospatial and memory dysfunction [1,2,3]. The default mode network (DMN) in the brain is consistently activated during a restingstate condition that is free from attention demands or cognitive load [4, 5]. The DMN is associated with a variety of cognitive functions, such as the theory of mind and social cognition [7], episodic memory [8], emotion and anxiety [9], and low-level attentional focus [10]. Abnormalities in the DMN have been observed in Alzheimer’s disease [11,12,13], schizophrenia [14], depression and anxiety [15], autism spectrum disorder [16], attention deficit/hyperactivity disorder [17], and many other conditions. Further investigations into the DMN could be a promising approach to unveil the underlying pathological mechanisms of multiple diseases

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