Fronto-Parietal Connectivity Is a Non-Static Phenomenon with Characteristic Changes during Unconsciousness

Untergehrer, G.; Jordan, Denis; Kochs, Eberhard; Ilg, Rüdiger; Schneider, Gerhard

doi:10.1371/journal.pone.0087498

Cited by 33 publications

(41 citation statements)

References 36 publications

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“…In fact, Untergehrer et al illustrated dynamic fluctuations in functional connectivity patterns, whereby maximum functional connectivity occurs during varying time intervals on a continuous scale, with surrogates of information transfer times being fastest during unconsciousness. 50 Accordingly, connectivity is a dynamic process and may need to cross certain real-time, continuous thresholds to correlate with varying levels of consciousness.…”

Section: Discussionmentioning

confidence: 99%

Neurophysiologic Correlates of Ketamine Sedation and Anesthesia

et al. 2017

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Background Previous studies have demonstrated inconsistent neurophysiologic effects of ketamine, although discrepant findings might relate to differences in doses studied, brain regions analyzed, coadministration of other anesthetic medications, and resolution of the electroencephalograph. The objective of this study was to characterize the dose-dependent effects of ketamine on cortical oscillations and functional connectivity. Methods Ten healthy human volunteers were recruited for study participation. The data were recorded using a 128-channel electroencephalograph during baseline consciousness, subanesthetic dosing (0.5 mg/kg over 40 min), anesthetic dosing (1.5 mg/kg bolus), and recovery. No other sedative or anesthetic medications were administered. Spectrograms, topomaps, and functional connectivity (weighted and directed phase lag index) were computed and analyzed. Results Frontal theta bandwidth power increased most dramatically during ketamine anesthesia (mean power ± SD, 4.25 ± 1.90 dB) compared to the baseline (0.64 ± 0.28 dB), subanesthetic (0.60 ± 0.30 dB), and recovery (0.68 ± 0.41 dB) states; P < 0.001. Gamma power also increased during ketamine anesthesia. Weighted phase lag index demonstrated theta phase locking within anterior regions (0.2349 ± 0.1170, P < 0.001) and between anterior and posterior regions (0.2159 ± 0.1538, P < 0.01) during ketamine anesthesia. Alpha power gradually decreased with subanesthetic ketamine, and anterior-to-posterior directed connectivity was maximally reduced (0.0282 ± 0.0772) during ketamine anesthesia compared to all other states (P < 0.05). Conclusions Ketamine anesthesia correlates most clearly with distinct changes in the theta bandwidth, including increased power and functional connectivity. Anterior-to-posterior connectivity in the alpha bandwidth becomes maximally depressed with anesthetic ketamine administration, suggesting a dose-dependent effect.

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Section: Discussionmentioning

confidence: 99%

Neurophysiologic Correlates of Ketamine Sedation and Anesthesia

et al. 2017

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“…Finally, since it has recently been shown that EEG directional connectivity shows characteristic changes during propofol-induced unconsciousness [41], the nature of BOLD peaks and their correlation with cortical activity needs to be explored using combined fMRI-EEG recordings.…”

Section: Discussionmentioning

confidence: 99%

Posterior Cingulate Cortex-Related Co-Activation Patterns: A Resting State fMRI Study in Propofol-Induced Loss of Consciousness

et al. 2014

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BackgroundRecent studies have been shown that functional connectivity of cerebral areas is not a static phenomenon, but exhibits spontaneous fluctuations over time. There is evidence that fluctuating connectivity is an intrinsic phenomenon of brain dynamics that persists during anesthesia. Lately, point process analysis applied on functional data has revealed that much of the information regarding brain connectivity is contained in a fraction of critical time points of a resting state dataset. In the present study we want to extend this methodology for the investigation of resting state fMRI spatial pattern changes during propofol-induced modulation of consciousness, with the aim of extracting new insights on brain networks consciousness-dependent fluctuations.MethodsResting-state fMRI volumes on 18 healthy subjects were acquired in four clinical states during propofol injection: wakefulness, sedation, unconsciousness, and recovery. The dataset was reduced to a spatio-temporal point process by selecting time points in the Posterior Cingulate Cortex (PCC) at which the signal is higher than a given threshold (i.e., BOLD intensity above 1 standard deviation). Spatial clustering on the PCC time frames extracted was then performed (number of clusters = 8), to obtain 8 different PCC co-activation patterns (CAPs) for each level of consciousness.ResultsThe current analysis shows that the core of the PCC-CAPs throughout consciousness modulation seems to be preserved. Nonetheless, this methodology enables to differentiate region-specific propofol-induced reductions in PCC-CAPs, some of them already present in the functional connectivity literature (e.g., disconnections of the prefrontal cortex, thalamus, auditory cortex), some others new (e.g., reduced co-activation in motor cortex and visual area).ConclusionIn conclusion, our results indicate that the employed methodology can help in improving and refining the characterization of local functional changes in the brain associated to propofol-induced modulation of consciousness.

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“…[1], [4]- [7]. To better understand this reduced information transfer and the underlying mechanisms, we complemented the reconstruction of information transfer with the estimation of local entropy measures.…”

Section: Discussionmentioning

confidence: 99%

“…This hypothesis is supported by various studies [1], [4]- [7], investigating anesthesia-induced changes in information transfer quantified by transfer entropy (TE) [8]. However, often this complex technique was applied using approximations, that may have detrimental effects on estimated TE values.…”

Section: Introductionmentioning

confidence: 92%

“…However, often this complex technique was applied using approximations, that may have detrimental effects on estimated TE values. The most prominent approximation in anesthesia research is the use of symbolic time series for TE *p.wollstadt@stud.uni-frankfurt.de estimation [4]- [7], [9]. Symbolic TE is a valuable method for TE estimation from small data sets, but also discards information that may be important for the reconstruction of information transfer [9], [10].…”

Section: Introductionmentioning

confidence: 99%

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Anesthesia-related changes in information transfer may be caused by reduction in local information generation

Sellers

Hutt

Fröhlich

et al. 2015

2015 37th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC)

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In anesthesia research it is an open question how general anesthetics lead to loss of consciousness (LOC). It has been proposed that LOC may be caused by the disruption of cortical information processing, preventing information integration. Therefore, recent studies investigating information processing under anesthesia focused on changes in information transfer, measured by transfer entropy (TE). However, often this complex technique was not applied rigorously, using time series in symbolic representation, or using TE differences without accounting for neural conduction delays, or without accounting for signal history. Here, we used current best-practice in TE estimation to investigate information transfer under anesthesia: We conducted simultaneous recordings in primary visual cortex (V1) and prefrontal cortex (PFC) of head-fixed ferrets in a dark environment under different levels of anesthesia (awake, 0.5% isoflurane, 1.0 % isoflurane). To elucidate reasons for changes in TE, we further quantified information processing within brain areas by estimating active information storage (AIS) as an estimator of predictable information, and Lempel-Ziv complexity (LZC) as an estimator of signal entropy. Under anesthesia, we found a reduction in information transfer (TE) between PFC and V1 with a stronger reduction for the feedback direction (PFC to V1), validating previous results. Furthermore, entropy (LZC) was reduced and activity became more predictable as indicated by higher values of AIS. We conclude that higher anesthesia concentrations indeed lead to reduced inter-areal information transfer, which may be partly caused by decreases in local entropy and increases in local predictability. In revealing a possible reason for reduced TE that is potentially independent of inter-areal coupling, we demonstrate the value of directly quantifying information processing in addition to focusing on dynamic properties such as coupling strength.

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Fronto-Parietal Connectivity Is a Non-Static Phenomenon with Characteristic Changes during Unconsciousness

Cited by 33 publications

References 36 publications

Neurophysiologic Correlates of Ketamine Sedation and Anesthesia

Neurophysiologic Correlates of Ketamine Sedation and Anesthesia

Posterior Cingulate Cortex-Related Co-Activation Patterns: A Resting State fMRI Study in Propofol-Induced Loss of Consciousness

Anesthesia-related changes in information transfer may be caused by reduction in local information generation

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