scholarly journals The absence of resting-state high-gamma cross-frequency coupling in patients with tinnitus

2017 ◽  
Vol 356 ◽  
pp. 63-73 ◽  
Author(s):  
Min-Hee Ahn ◽  
Sung Kwang Hong ◽  
Byoung-Kyong Min
Keyword(s):  
Resting State ◽  
High Gamma ◽  
Frequency Coupling ◽  
Cross Frequency Coupling

scholarly journals Altered cross-frequency coupling in resting-state MEG after mild traumatic brain injury

2016 ◽  
Vol 102 ◽  
pp. 1-11 ◽  
Author(s):  
Marios Antonakakis ◽  
Stavros I. Dimitriadis ◽  
Michalis Zervakis ◽  
Sifis Micheloyannis ◽  
Roozbeh Rezaie ◽  
...  
Keyword(s):  
Traumatic Brain Injury ◽  
Brain Injury ◽  
Mild Traumatic Brain Injury ◽  
Resting State ◽  
Frequency Coupling ◽  
Cross Frequency Coupling

scholarly journals Dissociating harmonic and non-harmonic phase-amplitude coupling in the human brain

2020 ◽  
Author(s):  
Janet Giehl ◽  
Nima Noury ◽  
Markus Siegel
Keyword(s):  
Human Brain ◽  
Resting State ◽  
Higher Harmonics ◽  
Spectral Leakage ◽  
Harmonic Phase ◽  
Harmonic Signals ◽  
Cast Doubt ◽  
Frequency Coupling ◽  
Phase Amplitude ◽  
Cross Frequency Coupling

AbstractPhase-amplitude coupling (PAC) has been hypothesized to coordinate cross-frequency interactions of neuronal activity in the brain. However, little is known about the distribution of PAC across the human brain and the frequencies involved. Furthermore, it remains unclear to what extend PAC may reflect spurious cross-frequency coupling induced by physiological artifacts or rhythmic non-sinusoidal signals with higher harmonics. Here, we combined MEG, source-reconstruction and different measures of cross-frequency coupling to systematically characterize PAC across the resting human brain. We show that cross-frequency measures of phase-amplitude, phase-phase, and amplitude-amplitude coupling are all sensitive to signals with higher harmonics. In conjunction, these measures allow to distinguish harmonic and non-harmonic PAC. Based on these insights, we found no evidence for non-harmonic PAC in resting-state MEG. Instead, we found cortically and spectrally wide-spread PAC driven by harmonic signals. Furthermore, we show how physiological artifacts and spectral leakage cause spurious PAC across wide frequency ranges. Our result clarify how different measures of cross-frequency interactions can be combined to characterize PAC and cast doubt on the presence of prominent non-harmonic phase-amplitude coupling in human resting-state MEG.

scholarly journals Distinct signatures of loss of consciousness during Focal Impaired Awareness (FIA) versus Focal to Bilateral Tonic-Clonic (FBTC) seizures

2021 ◽  
Author(s):  
Elsa Juan ◽  
Urszula Gorska ◽  
Csaba Kozma ◽  
Cynthia Papantonatos ◽  
Tom Bugnon ◽  
...  
Keyword(s):  
Unit Activity ◽  
Clinical Signs ◽  
Neuronal Firing ◽  
Cortical Activation ◽  
Loss Of Consciousness ◽  
Subsequent Increase ◽  
High Gamma ◽  
Impaired Awareness ◽  
Frequency Coupling ◽  
Cross Frequency Coupling

Loss of consciousness (LOC) is a hallmark of many epileptic seizures and carries risks of serious injury and sudden death. While cortical sleep-like activities accompany LOC during focal impaired awareness (FIA) seizures, the mechanisms of LOC during focal to bilateral tonic-clonic (FBTC) seizures remain unclear. Quantifying differences in markers of cortical activation and ictal recruitment between FIA and FBTC seizures may also help to understand their different consequences for clinical outcomes and to optimize neuromodulation therapies. We quantified clinical signs of LOC and intracranial EEG (iEEG) activity during 129 FIA and 50 FBTC from 41 patients. We characterized iEEG changes both in the seizure onset zone (SOZ) and in areas remote from SOZ with a total of 3386 electrodes distributed across brain areas. First, we compared the dynamics of iEEG sleep-like activities: slow-wave activity (SWA; 1-4 Hz) and beta/delta ratio (B/D; a validated marker of cortical activation) during FIA vs. FBTC. Second, we quantified differences between FBTC and FIA for a marker validated to detect ictal cross-frequency coupling: phase-locked high-gamma (PLHG; high gamma phased locked to low frequencies) and a marker of ictal recruitment: the epileptogenicity index (i.e. the number of channels crossing an energy ratio threshold for high vs. low frequency power). Third, we assessed changes in iEEG activity preceding and accompanying behavioral generalization onset and their correlation with electromyogram (EMG) channels. In addition, we analyzed human cortical multi-unit activity recorded with Utah arrays during three FBTC. Compared to FIA, FBTC seizures were characterized by deeper LOC and by stronger increases in SWA in parieto-occipital cortex. FBTC also displayed more widespread increases in cortical activation (B/D), ictal cross-frequency coupling (PLHG) and ictal recruitment (epileptogenicity index). Even before generalization, FBTC displayed deeper LOC; this early LOC was accompanied by a paradoxical increase in B/D in fronto-parietal cortex. Behavioral generalization coincided with complete loss of responsiveness and a subsequent increase in high-gamma in the whole brain, which was especially synchronous in deep sources and could not be explained by EMG. Similarly, multi-unit activity analysis of FBTC revealed sustained increases in cortical firing rates during and after generalization onset in areas remote from the SOZ. Unlike during FIA, LOC during FBTC is characterized by a paradoxical increase in cortical activation and neuronal firing. These findings suggest differences in the mechanisms of ictal LOC between FIA and FBTC and may account for the more negative prognostic consequences of FBTC.

scholarly journals Aberrant resting-state functional brain networks in dyslexia: Symbolic mutual information analysis of neuromagnetic signals

2018 ◽  
Author(s):  
Stavros I. Dimitriadis ◽  
Panagiotis G. Simos ◽  
Jack M. Fletcher ◽  
Andrew C. Papanicolaou
Keyword(s):  
Reading Achievement ◽  
Resting State ◽  
Cost Efficiency ◽  
Reading Difficulties ◽  
Global Network ◽  
List Type ◽  
Global Cost ◽  
Symbolic Sequences ◽  
Frequency Coupling ◽  
Cross Frequency Coupling

AbstractNeuroimaging studies have identified a variety of structural and functional connectivity abnormalities in students experiencing reading difficulties. The present study adopted a novel approach to assess the dynamics of resting-state neuromagnetic recordings in the form of symbolic sequences (i.e., repeated patterns of neuromagnetic fluctuations within and/or between sensors).Participants were 25 students experiencing severe reading difficulties (RD) and 27 age-matched non-impaired readers (NI) aged 7-14 years. Sensor-level data were first represented as symbolic sequences in eight conventional frequency bands. Next, dominant types of sensor-to-sensor interactions in the form of intra and cross-frequency coupling were computed and subjected to graph modeling to assess group differences in global network characteristics.As a group RD students displayed predominantly within-frequency interactions between neighboring sensors which may reflect reduced overall global network efficiency and cost-efficiency of information transfer. In contrast, sensor networks among NI students featured a higher proportion of cross-frequency interactions. Brain-reading achievement associations highlighted the role of left hemisphere temporo-parietal functional networks, at rest, for reading acquisition and ability.HighlightsSymbolic dynamics of MEG time series revealed aberrant Cross Frequency Coupling in RD studentsGlobal efficiency and strength of Cross Frequency Coupling could reliably identify RD students from age-matched controlsGlobal Cost Efficiency, coupling strength, and the relative preponderance of cross-frequency interactions strongly correlated with reading achievement across groups.

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