Mean phase coherence as a measure for phase synchronization and its application to the EEG of epilepsy patients

Mormann, Florian; Lehnertz, Klaus; David, Peter; Elger, Christian E.

doi:10.1016/s0167-2789(00)00087-7

Cited by 1,170 publications

(887 citation statements)

References 32 publications

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“…Interelectrode synchrony was measured using the mean phase coherence (MPC) algorithm (Mormann, Lehnertz et al 2000) and implemented in Matlab. This algorithm measures phase locking of broad-band EEG signals from two electrodes independent of their predominant phase angles.…”

Section: Methodsmentioning

confidence: 99%

“…We report an investigation into spatial patterns of local synchrony in epilepsy patients with medically refractory partial epilepsy using a measure of phase coherence in wide-band ICEEG signals (Mormann, Lehnertz et al 2000). Based on synchrony measurements of the EEG signals recorded from orthogonally adjacent pairs of electrodes in subdural grids, we are able to define regions of local hypersynchrony (LH) in which there are markedly higher levels of synchrony compared to surrounding brain regions.…”

Section: Introductionmentioning

confidence: 99%

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Cortical abnormalities in epilepsy revealed by local EEG synchrony

et al. 2007

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Abnormally strong functional linkage between cortical areas has been postulated to play a role in the pathogenesis of partial epilepsy. We explore the possibility that such linkages may be manifest in the interictal EEG apart from epileptiform disturbances or visually evident focal abnormalities. We analyzed samples of interictal intracranial EEG (ICEEG) recorded from subdural grids in nine patients with medically intractable partial epilepsy, measuring interelectrode synchrony using the mean phase coherence algorithm. This analysis revealed areas of elevated local synchrony, or "hypersynchrony" which had persistent spatiotemporal characteristics that were unique to each patient. Measuring local synchrony in a subdural grid results in a map of the cortical surface that provides information not visually apparent on either EEG or structural imaging. We explore the relationship of hypersynchronous areas to the clinical evidence of seizure localization in each case, and speculate that local hypersynchrony may be a marker of epileptogenic cortex, and may prove to be a valuable aid to clinical ICEEG interpretation.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Cortical abnormalities in epilepsy revealed by local EEG synchrony

et al. 2007

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“…In order to provide additional information to the measures widely used in the study of functional connectivity in dementia (coherence and synchronization likelihood), PLV (Mormann et al 2000) between pairs of sensors was computed. To avoid mixing signals of different nature and noise profiles, we used only magnetometers for this functional connectivity analysis (we note however that gradiometers were used in the temporal signal space separation step, so the resulting magnetometer data contain indirectly gradiometer information).…”

Section: Functional Connectivity Analysismentioning

confidence: 99%

Synchronization during an internally directed cognitive state in healthy aging and mild cognitive impairment: a MEG study

López

Garcés

Cuesta

et al. 2014

AGE

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Mild cognitive impairment (MCI) is a stage between healthy aging and dementia. It is known that in this condition the connectivity patterns are altered in the resting state and during cognitive tasks, where an extra effort seems to be necessary to overcome cognitive decline. We aimed to determine the functional connectivity AGE (2014) pattern required to deal with an internally directed cognitive state (IDICS) in healthy aging and MCI. This task differs from the most commonly employed ones in neurophysiology, since inhibition from external stimuli is needed, allowing the study of this control mechanism. To this end, magnetoencephalographic (MEG) signals were acquired from 32 healthy individuals and 38 MCI patients, both in resting state and while performing a subtraction task of two levels of difficulty. Functional connectivity was assessed with phase locking value (PLV) in five frequency bands. Compared to controls, MCIs showed higher PLV values in delta, theta, and gamma bands and an opposite pattern in alpha, beta, and gamma bands in resting state. These changes were associated with poorer neuropsychological performance. During the task, this group exhibited a hypersynchronization in delta, theta, beta, and gamma bands, which was also related to a lower cognitive performance, suggesting an abnormal functioning in this group. Contrary to controls, MCIs presented a lack of synchronization in the alpha band which may denote an inhibition deficit. Additionally, the magnitude of connectivity changes rose with the task difficulty in controls but not in MCIs, in line with the compensation-related utilization of neural circuits hypothesis (CRUNCH) model.

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“…The variable r(t i ) is also known as mean phase coherence (Morman et al 2000), and is equivalent to (1 minus the) circular variance (Fisher 1993 (Mormann et al 2000). As signals become more coherent in phase, both phase amplitude and angle dispersion should decrease.…”

Section: Dynamical Measuresmentioning

confidence: 99%

Neuronal spatiotemporal pattern discrimination: The dynamical evolution of seizures

Kumar²,

2005

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We developed a modern numerical approach to the multivariate linear discrimination of Fisher from 1936 based upon singular value decomposition that is sufficiently stable to permit widespread application to spatiotemporal neuronal patterns. We demonstrate this approach on an old problem in neuroscience -whether seizures have distinct dynamical states as they evolve with time. A practical result was the first demonstration that human seizures have distinct initiation and termination dynamics, an important characterization as we seek to better understand how seizures start and stop. Our approach is broadly applicable to a wide variety of neuronal data, from multichannel EEG or MEG, to sequentially acquired optical imaging data or fMRI.

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Mean phase coherence as a measure for phase synchronization and its application to the EEG of epilepsy patients

Cited by 1,170 publications

References 32 publications

Cortical abnormalities in epilepsy revealed by local EEG synchrony

Cortical abnormalities in epilepsy revealed by local EEG synchrony

Synchronization during an internally directed cognitive state in healthy aging and mild cognitive impairment: a MEG study

Neuronal spatiotemporal pattern discrimination: The dynamical evolution of seizures

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