An Electrophysiological Marker of Arousal Level in Humans

Lendner, Janna D.; Helfrich, Randolph F.; Mander, Bryce A.; Romundstad, Luis; Lin, Jack J.; Walker, Matthew P.; Larsson, Pål G.; Knight, Robert T.

doi:10.1101/625210

Cited by 17 publications

(24 citation statements)

References 65 publications

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“…At the same level of behavioral unresponsiveness, propofol and sevoflurane induced a spontaneous EEG activity characterized by high amplitude, low frequency waves, while ketamine anesthesia yielded sustained, fast, desynchronized EEG activity, resembling the awake state. In agreement with previous studies in humans (Colombo et al, 2019;Lendner et al, 2019), the spectral exponent of the relative periodogram (20-40 Hz) was reduced by propofol and sevoflurane, but with ketamine it remained similar to wakefulness (Fig. 1, Fig.…”

Section: Discussionsupporting

confidence: 92%

General Anesthesia Disrupts Complex Cortical Dynamics in Response to Intracranial Electrical Stimulation in Rats

Arena

Comolatti

Thon

et al. 2021

eNeuro

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We would like to thank Per M. Knutsen for help in preparation of the experimental set-up and Charlotte Boccara for advice regarding the writing. We are especially grateful to Marcello Massimini, Andrea Pigorini, Matteo Fecchio and Simone Russo for their valuable comments, suggestions, and support along the way. Renzo Comolatti's current affiliation: Department of Biomedical and Clinical Sciences "L.

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Section: Discussionsupporting

confidence: 92%

General Anesthesia Disrupts Complex Cortical Dynamics in Response to Intracranial Electrical Stimulation in Rats

Arena

Comolatti

Thon

et al. 2021

eNeuro

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show abstract

“…At the same level of behavioural unresponsiveness, propofol and sevoflurane induced a spontaneous EEG activity characterized by high amplitude, low frequency waves, while ketamine anaesthesia yielded sustained fast, desynchronized EEG activity, resembling the awake state. In agreement with previous studies 30,31 , the spectral exponent of the relative periodogram (20-40 Hz) was reduced by propofol and sevoflurane, but with ketamine it remained similar to wakefulness ( Fig. 1, 4, Supplementary Fig.…”

Section: Discussionsupporting

confidence: 92%

General anaesthesia disrupts complex cortical dynamics in response to intracranial electrical stimulation in rats

Arena

Comolatti

Thon

et al. 2020

Preprint

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The capacity of the human brain to sustain complex dynamics consistently drops when consciousness fades. Several recent studies in humans found a remarkable reduction of the complexity of cortical responses to local stimulation during dreamless sleep, general anaesthesia, and coma. So far, this perturbational complexity has never been estimated in non-human animals in vivo. Here, we quantify the complexity of electroencephalographic responses to intracranial electrical stimulation in rats, comparing wakefulness to propofol, sevoflurane, and ketamine anaesthesia. We confirm the changes previously observed in humans: from highly complex evoked activity during wakefulness, to simpler responses, suppression of high frequencies, and reduced phase-locking with propofol and sevoflurane.We then deepen our mechanistic understanding by analyzing functional connectivity, and by showing how these parameters dissociate with ketamine, and depend on intensity and site of stimulation. This approach opens the way for further direct investigations of the mechanisms underlying brain complexity and consciousness. hypothesis that neuronal hyperpolarization might prevent cortical neurons from engaging in durable, complex interactions 12,13,14,15 . RESULTS Single pulse electrical stimulation triggered complex ERPs during wakefulness, but not during propofol anaesthesiaWe recorded epidural EEG activity from 16 screw electrodes chronically implanted through the skull in head-and body-restrained male, adult rats. Recording electrodes were in contact with the dura and organized in a symmetric grid, covering most of the cortex in both hemispheres (M2, secondary motor cortex; M1, primary motor cortex; S1, primary somatosensory cortex; RS, retrosplenial cortex; PA, parietal associative cortex; V1, primary visual cortex; V2, secondary visual cortex; GND, ground electrode over cerebellum). We stimulated right M2 by single monophasic, electrical current pulses (typically: 1 ms duration, 50 µA amplitude, at 0.1 Hz) via a chronically implanted bipolar electrode, located 4.38 ± 0.26 mm rostral from bregma, 0.47 ± 0.09 mm below the cortical surface, mainly corresponding to layer II/III (based on histology after recording, 8 rats; Fig. 1a; all values are reported as mean ± SEM). Pulse trains delivered at similar coordinates triggered coordinated whisker deflections 16 , whereas EEG responses following single stimuli were not measurably contaminated by movements ( Supplementary Fig. 1, Video 1-2) and were reproducible throughout recording sessions and across days (Supplementary Fig. 2). No correlation between the stimulating electrode locations and ERP amplitude or duration was found (Supplementary Fig. 3).We performed electrophysiological recordings in 9 rats during wakefulness and propofol anaesthesia (∼1.1 mg/kg/min, i.v.) at a depth that produced spontaneous, slow, high-amplitude EEG oscillations and was sufficient to abolish any detectable motor response to pain stimuli. The redistribution of EEG power from high to low frequencies was confirmed ...

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“…For example, when band ratios are used in sleep scoring, it is typically done with the delta / theta ratio, which we predict likely also captures aperiodic changes. This would be consistent with recent reports that aperiodic activity changes systematically with sleep (Lendner et al, 2020). Collectively, these shared correlates are consistent with the suggestion that band ratio measures likely often reflect aperiodic activity.…”

Section: Interpretation Related Discussion Pointssupporting

confidence: 92%

Electrophysiological Frequency Band Ratio Measures Conflate Periodic and Aperiodic Neural Activity

Donoghue

Dominguez

Voytek

2020

eNeuro

134

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Band ratio measures, computed as the ratio of power between two frequency bands, are a common analysis measure in neuro-electrophysiological recordings. Band ratio measures are typically interpreted as reflecting quantitative measures of periodic, or oscillatory, activity. This assumes that the measure reflects relative powers of distinct periodic components that are well captured by predefined frequency ranges. However, electrophysiological signals contain periodic components and a 1/f-like aperiodic component, the latter of which contributes power across all frequencies. Here, we investigate whether band ratio measures truly reflect oscillatory power differences, and/or to what extent ratios may instead reflect other periodic changes-such as in center frequency or bandwidth-and/or aperiodic activity. In simulation, we investigate how band ratio measures relate to changes in multiple spectral features, and show how multiple periodic and aperiodic features influence band ratio measures. We validate these findings in human electroencephalography (EEG) data, comparing band ratio measures to parameterizations of power spectral features, and find that multiple disparate features influence ratio measures. For example, the commonly applied theta / beta ratio is most reflective of differences in aperiodic activity, and not oscillatory theta or beta power. Collectively, we show that periodic and aperiodic features can create the same observed changes in band ratio measures, and that this is inconsistent with their typical interpretations as measures of periodic power. We conclude that band ratio measures are a non-specific measure, conflating multiple possible underlying spectral changes, and recommend explicit parameterization of neural power spectra as a more specific approach. Band Ratios 3 Significance Statement Neural oscillations are a ubiquitous feature of investigation in electrophysiological recordings. Frequency band ratio measures are a common approach to investigate neural oscillations, applied across cognitive and clinical neuroscience, and in recording modalities such as in electroencephalography and local field potentials. In this work we systematically investigate the methodological properties of band ratio measures. We show that band ratio measures are not specific to measuring oscillatory power, as they are intended and interpreted to do. Rather, they often reflect other features of the data, such as aperiodic, or 1/f-like, activity. These findings are significant for interpreting prior empirical and clinical research, guiding future work, and another motivation that aperiodic neural activity should be a key consideration when studying electrophysiological data.

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An Electrophysiological Marker of Arousal Level in Humans

Abstract: 2 1

Cited by 17 publications

References 65 publications

General Anesthesia Disrupts Complex Cortical Dynamics in Response to Intracranial Electrical Stimulation in Rats

General Anesthesia Disrupts Complex Cortical Dynamics in Response to Intracranial Electrical Stimulation in Rats

General anaesthesia disrupts complex cortical dynamics in response to intracranial electrical stimulation in rats

Electrophysiological Frequency Band Ratio Measures Conflate Periodic and Aperiodic Neural Activity

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