Aperiodic EEG activity masks the dynamics of neural oscillations during loss of consciousness from propofol

EEGs are known to provide biomarkers for consciousness. Although EEG correlates of loss of consciousness (LOC) are often ascribed to changes in neural synchrony, mounting evidence suggests that some changes result from asynchronous neural activity. By combining EEG recordings of humans undergoing propofol administration with biophysical modelling, we present here a principled decomposition of EEG changes during LOC into synchronous and asynchronous sources. Our results reveal that IPSP decay rate and mean spike rate shape aperiodic EEG features, and that propofol's effects on these parameters largely explain the changes in EEG spectra following propofol infusion. We further show that traditional spectral EEG analysis likely conflates these effects with changes in rhythmic activity, thereby masking the true dynamics of neural synchrony. We conclude that the well-documented propofol-induced alpha rhythm in fact appears before LOC, and that the moment of LOC is uniquely correlated with the sudden appearance of a delta rhythm.

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Differentiating motor phenomena in tilt-induced syncope and convulsive seizures

Neurology ◽

10.1212/wnl.0000000000005301 ◽

2018 ◽

Vol 90 (15) ◽

pp. e1339-e1346 ◽

Cited By ~ 17

Author(s):

Sharon Shmuely ◽

Prisca R. Bauer ◽

Erik W. van Zwet ◽

J. Gert van Dijk ◽

Roland D. Thijs

Keyword(s):

Blood Pressure ◽

Differential Diagnosis ◽

Convulsive Seizure ◽

Loss Of Consciousness ◽

Blood Pressure Decrease ◽

Pressure Decrease ◽

Eeg Changes ◽

Eeg Recordings ◽

Convulsive Seizures ◽

Video Eeg

ObjectiveWe assessed motor phenomena in syncope and convulsive seizures to aid differential diagnosis and understand the pathophysiologic correlates.MethodsWe studied video-EEG recordings of tilt-induced syncope and convulsive seizures in participants aged 15 years and older. Syncope was defined as (1) loss of consciousness (video-assessed), (2) circulatory changes (accelerating blood pressure decrease with or without bradycardia/asystole), and (3) EEG changes (“slow” or “slow-flat-slow”). We assessed myoclonic jerks and tonic postures of the arms and noted time of occurrence, laterality, synchrony, and rhythmicity (mean consecutive differences of interclonic intervals).ResultsVideo-EEG records of 65 syncope cases and 50 convulsive seizures were included. In syncope, postures occurred in 42 cases (65%) and jerks in 33 (51%). Fewer jerks occurred in syncope (median 2, range 1–19) compared to convulsive seizures (median 48, range 20–191; p < 0.001). Jerks were more rhythmic in seizures compared to syncope (p < 0.001). Atonia was seen in all syncope cases, while this was not observed in any seizure. Jerks predominantly occurred during the slow and postures during the flat EEG phase.ConclusionsJerks and tonic postures were common in syncope, but semiology differed from convulsive seizures. The lack of overlap in the number of jerks suggests that less than 10 indicates syncope and more than 20 a convulsive seizure: the “10/20 rule.” Loss of tone strongly favors syncope. The EEG correlates imply that jerks in syncope are likely of cortical origin, whereas tonic postures may result from brainstem disinhibition.

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The meaning of EEG indicators of loss of consciousness during anaesthesia and coma.

10.31234/osf.io/u2cg7 ◽

2021 ◽

Author(s):

Costa Vakalopoulos

Keyword(s):

Resting State ◽

Visual Information ◽

Alpha Rhythm ◽

Loss Of Consciousness ◽

Cognitive Effects ◽

The Unconscious ◽

Gaba Agonist ◽

Explicit Cognition ◽

Eeg Changes ◽

Minimally Conscious

Raw EEG changes correlate well with the effects of anaesthetics on arousal. The purpose ofthe present paper is to analyse the significance of the EEG spectrograph. The alpha rhythm isa signature of the unconscious and according to the MAB hypothesis (Monoaminergic-Acetylcholinergic Balance) is an index of increased relative inhibitory muscarinic effects onmonoaminergic modulated conscious networks. The source of alpha rhythms varies, as doesthe type of unconscious information: from classical occipital alpha during resting state witheyes closed where no external visual information is processed, to states of unconsciousanaesthesia where alpha shifts to fronto-parietal networks. These are spontaneous oscillatorynetwork responses and the effects of GABA agonist anaesthetics increase the amplitude ofthese intrinsic rhythms. The hypothesis states that the concurrent presence of sustained deltaoscillations and alpha spindles signifies suppressed unconscious and conscious responsesrespectively, and permit neither implicit nor explicit cognition nor recollections. Further, themodel will be used to interpret EEG changes associated with more atypical anaesthetics andprovide reasons for the related cognitive effects. This will be based on the agents’pharmacological profiles and how they interact with these dual neuromodulatory systems.Evidence will also be drawn from EEG states associated with pathophysiology in coma andepilepsy. The pharmacological interpretation of EEG makes predictions of awareness indisorders of consciousness. The difficult circumstances of behaviourally inadequateindicators refers to situations of minimally conscious and in particular, vegetative stateswhere decision making is fraught with uncertainty.

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Electroencephalogram indices in patients undergoing cardiac arrest

Medical alphabet ◽

10.33667/2078-5631-2020-14-32-38 ◽

2020 ◽

Vol 1 (14) ◽

pp. 32-38

Author(s):

I. Yu. Berezina ◽

L. I. Sumsky ◽

A. Yu. Mikhailov ◽

Yu. L. Arzumanov

Keyword(s):

Cardiac Arrest ◽

Electrical Activity ◽

Paroxysmal Activity ◽

Equivalent Dipole ◽

Neurophysiological Mechanisms ◽

Eeg Changes ◽

Eeg Recordings ◽

The Moment ◽

Electroencephalogram Eeg ◽

The Brain

Objective: to assess the safety of indicators of electrical activity of the brain for the approach to the analysis of the basic neurophysiological mechanisms of the brain in patients after cardiac arrest.Materials and methods: 52 patients were examined (age — 54,68 ± 19,33) after cardiac arrest. At the time of recording the electroencephalogram (EEG), the level of wakefulness of the examined patients on the Glasgow coma scale was in the range of 3 to 13 points. In 35 patients, EEG recording was performed starting from the first three days from the moment of cardiac arrest, in 17 patients — from the fourth to the 18th day. EEG was registered on electroencephalographs ‘Encephalan–EEGR–19/26’ by ‘Medikom MTD’, ‘Neuron-Spectrum–5/EP’ and ‘Neuron-Spectrum–65’ by ‘Neurosoft’ in accordance with the recommendations of the International Federation of Clinical Neurophysiologists (IFCN). The duration of a single EEG recordings lasted at least 30 min. To localize equivalent dipole sources of pathological activity we used the program ‘BrainLoc 6.0’, (Russia). In 19 patients EEG was recorded in dynamics from 2 to 8 times.Results: all patients showed EEG changes of varying severity, which can be divided into three groups (according to the severity of changes in the EEG: moderate, severe and rough). In the group of patients with gross changes in EEG can be identified 4 variants: the first variant — absence of the alpha rhythm and the dominance of slow-wave fluctuations of the frequency spectrum; variant II — continuous generalized paroxysmal activity; variant III — phenomenon of ‘burst-suppression’; variant IV — a marked decrease in the amplitude of electrical activity of the brain to the level of 2–4 microvolt.Conclusions: based on the dynamics of the EEG pattern in patients after cardiac arrest, it is possible to assume with a certain degree of probability the level of violations in the basic mechanisms of the brain.

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Sounding It Out: Auditory Stimulation and Overnight Memory Processing

Current Sleep Medicine Reports ◽

10.1007/s40675-021-00207-0 ◽

2021 ◽

Author(s):

Marcus O. Harrington ◽

Scott A. Cairney

Keyword(s):

Rem Sleep ◽

Memory Consolidation ◽

Slow Wave Sleep ◽

Auditory Stimulation ◽

Theta Oscillations ◽

Neural Oscillations ◽

Healthy Children ◽

Factors Affecting ◽

Memory Processing ◽

Eeg Recordings

Abstract Purpose of Review Auditory stimulation is a technique that can enhance neural oscillations linked to overnight memory consolidation. In this review, we evaluate the impacts of auditory stimulation on the neural oscillations of sleep and associated memory processes in a variety of populations. Recent Findings Cortical EEG recordings of slow-wave sleep (SWS) are characterised by two cardinal oscillations: slow oscillations (SOs) and sleep spindles. Auditory stimulation delivered in SWS enhances SOs and phase-coupled spindle activity in healthy children and adults, children with ADHD, adults with mild cognitive impairment and patients with major depression. Under certain conditions, auditory stimulation bolsters the benefits of SWS for memory consolidation, although further work is required to fully understand the factors affecting stimulation-related memory gains. Recent work has turned to rapid eye movement (REM) sleep, demonstrating that auditory stimulation can be used to manipulate REM sleep theta oscillations. Summary Auditory stimulation enhances oscillations linked to overnight memory processing and shows promise as a technique for enhancing the memory benefits of sleep.

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Migraine with Prolonged Aura: Correlation of Clinical and EEG Features

Behavioural Neurology ◽

10.1155/1995/139835 ◽

1995 ◽

Vol 8 (2) ◽

pp. 109-114 ◽

Cited By ~ 3

Author(s):

A. O. Ogunyemi

Keyword(s):

Cerebral Cortex ◽

Migraine With Aura ◽

Slow Waves ◽

Spreading Cortical Depression ◽

Eeg Abnormalities ◽

Cortical Depression ◽

Eeg Changes ◽

Eeg Recordings ◽

The Brain

Migraine with prolonged aura has rarely been examined with regard to the sequence of the neurological symptoms and the associated EEG changes. This report describes five patients who underwent clinical assessment and EEG recordings during attacks of migraine with prolonged aura. CT scan of the brain was obtained in four of them. Follow-up EEG was also obtained. The aura symptoms either preceded the headache or were coincident with it. The aura symptoms evolved in a manner consistent with posterior-to-anterior dysfunction of the cerebral cortex. The EEG abnormalities were non-epileptiform and consisted of focal delta slow waves or theta slow waves. The EEG abnormalities showed good correlation with the patients' aura symptoms and resolved when the patients became symptom free. The posterior-to-anterior sequence of the aura symptoms is in accord with the findings during cerebral blood flow studies in patients having migraine with aura. Also the symptoms and EEG changes in our patients indicate dysfunction of the cerebral cortex, consistent with the notion that spreading cortical depression may be the underlying pathophysiological event in migraine with aura.

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Coherence analysis of EEG changes during odour stimulation in humans

The Journal of Laryngology & Otology ◽

10.1017/s0022215100134528 ◽

1996 ◽

Vol 110 (7) ◽

pp. 652-656 ◽

Cited By ~ 6

Author(s):

Hirofumi Harada ◽

Kimio Shiraishi ◽

Toshihiko Kato ◽

Toyoji Soda

Keyword(s):

Broad Band ◽

Frontal Region ◽

Coherence Analysis ◽

Temporal Region ◽

Eeg Coherence ◽

Frequency Bands ◽

Delta Band ◽

Eeg Changes ◽

Eeg Recordings ◽

And Control

AbstractIn a pilot study, EEG changes during odour administration were evaluated by coherence analysis. Ten normal adults were studied. Simultaneous recordings of 16 EEG channels with, and without, odour administration were stored on magnetic tape for further processing. EEG signals were analysed using a signal analyser. Coherence spectra were calculated between all possible channel pairs on the scalp. The amount of data was reduced by extracting broad band coherence values for five frequency bands: delta (2–3.9 Hz), theta (4–7.9 Hz), alpha 1 (8–9.9 Hz), alpha 2 (10–12.9 Hz), and beta 1 (13–17.9 Hz). Coherence values extracted from the control EEG recordings and those during odour administration were compared to evaluate the presence of any significant differences.The results demonstrated significant changes in the EEG coherence between the two control recordings (control before and control after) in the theta and beta 1 bands. These frequency bands were therefore excluded from the examination. During odorant stimulation with methyl-cyclopentenolone, the coherence in the delta band decreased in the frontal region, while that in the alpha 1 and alpha 2 bands increased in the temporal region. During odorant stimulation with scatol, the coherence in the delta band decreased in the frontal region, while that in the alpha 1 and alpha 2 bands increased between the longitudinal electrode locations. It was suggested that EEG coherence mapping may provide the basis for the development of an objective test of olfactory function in humans.

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Detection of Hypoglycemia Using Measures of EEG Complexity in Type 1 Diabetes Patients

Entropy ◽

10.3390/e22010081 ◽

2020 ◽

Vol 22 (1) ◽

pp. 81 ◽

Cited By ~ 2

Author(s):

Maria Rubega ◽

Fabio Scarpa ◽

Debora Teodori ◽

Anne-Sophie Sejling ◽

Christian S. Frandsen ◽

...

Keyword(s):

Type 1 Diabetes ◽

Single Channel ◽

Permutation Entropy ◽

Eeg Signals ◽

Scalp Eeg ◽

Power Spectral ◽

Eeg Changes ◽

Eeg Recordings ◽

Clamp Study

Previous literature has demonstrated that hypoglycemic events in patients with type 1 diabetes (T1D) are associated with measurable scalp electroencephalography (EEG) changes in power spectral density. In the present study, we used a dataset of 19-channel scalp EEG recordings in 34 patients with T1D who underwent a hyperinsulinemic–hypoglycemic clamp study. We found that hypoglycemic events are also characterized by EEG complexity changes that are quantifiable at the single-channel level through empirical conditional and permutation entropy and fractal dimension indices, i.e., the Higuchi index, residuals, and tortuosity. Moreover, we demonstrated that the EEG complexity indices computed in parallel in more than one channel can be used as the input for a neural network aimed at identifying hypoglycemia and euglycemia. The accuracy was about 90%, suggesting that nonlinear indices applied to EEG signals might be useful in revealing hypoglycemic events from EEG recordings in patients with T1D.

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Fast-spiking Interneurons Contribute to Propofol-induced Facilitation of Firing Synchrony in Pyramidal Neurons of the Rat Insular Cortex

Anesthesiology ◽

10.1097/aln.0000000000003653 ◽

2020 ◽

Author(s):

Yuko Koyanagi ◽

Yoshiyuki Oi ◽

Masayuki Kobayashi

Keyword(s):

Pyramidal Neuron ◽

Alpha Rhythm ◽

Pyramidal Neurons ◽

Average Distance ◽

Spike Timing ◽

Spiking Neurons ◽

Loss Of Consciousness ◽

Spiking Neuron ◽

Absolute Value ◽

Fast Spiking

Background: The general anesthetic propofol induces frontal alpha rhythm in the cerebral cortex at a dose sufficient to induce loss of consciousness. The authors hypothesized that propofol-induced facilitation of unitary inhibitory postsynaptic currents would result in firing synchrony among postsynaptic pyramidal neurons that receive inhibition from the same presynaptic inhibitory fast-spiking neurons. Methods: Multiple whole cell patch clamp recordings were performed from one fast-spiking neuron and two or three pyramidal neurons with at least two inhibitory connections in rat insular cortical slices. The authors examined how inhibitory inputs from a presynaptic fast-spiking neuron modulate the timing of spontaneous repetitive spike firing among pyramidal neurons before and during 10 μM propofol application. Results: Responding to activation of a fast-spiking neuron with 150-ms intervals, pyramidal cell pairs that received common inhibitory inputs from the presynaptic fast-spiking neuron showed propofol-dependent decreases in average distance from the line of identity, which evaluates the coefficient of variation in spike timing among pyramidal neurons: average distance from the line of identity just after the first activation of fast-spiking neuron was 29.2 ± 24.1 (mean ± SD, absolute value) in control and 19.7 ± 19.2 during propofol application (P < 0.001). Propofol did not change average distance from the line of identity without activating fast-spiking neurons and in pyramidal neuron pairs without common inhibitory inputs from presynaptic fast-spiking neurons. The synchronization index, which reflects the degree of spike synchronization among pyramidal neurons, was increased by propofol from 1.4 ± 0.5 to 2.3 ± 1.5 (absolute value, P = 0.004) and from 1.5 ± 0.5 to 2.2 ± 1.0 (P = 0.030) when a presynaptic fast-spiking neuron was activated at 6.7 and 10 Hz, respectively, but not at 1, 4, and 13.3 Hz. Conclusions: These results suggest that propofol facilitates pyramidal neuron firing synchrony by enhancing inhibitory inputs from fast-spiking neurons. This synchrony of pyramidal neurons may contribute to the alpha rhythm associated with propofol-induced loss of consciousness. Editor’s Perspective What We Already Know about This Topic What This Article Tells Us That Is New

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Electroencephalographic Indices for Diagnosis of Delirium

International Psychogeriatrics ◽

10.1017/s1041610291000704 ◽

1991 ◽

Vol 3 (2) ◽

pp. 249-251 ◽

Cited By ~ 3

Author(s):

Hannu Koponen

Keyword(s):

Central Nervous System ◽

Nervous System ◽

Slow Wave ◽

Alpha Rhythm ◽

Wave Activity ◽

Laboratory Procedure ◽

Electrical Potentials ◽

The Central Nervous System ◽

Eeg Changes ◽

Serial Evaluation

The central nervous system electrical potentials recorded by the EEG are sensitive to alterations in the levels of consciousness and attention (Mesulam, 1986). Thus it is understandable that previous studies on delirious patients using routine EEGs have shown an increase of slow-wave activity and slowing and disruption of the normal alpha rhythm (Romano & Engel, 1944). At present, the electrocephalogram is widely accepted as a valuable ancillary laboratory procedure for diagnosis and serial evaluation of delirium, as EEG changes often accompany delirium.

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Pitfalls in EEG analysis in patients with non-convulsive status epilepticus

10.1101/2020.10.02.20205583 ◽

2020 ◽

Author(s):

Ying Wang ◽

Ivan C Zibrandtsen ◽

Richard HC Lazeron ◽

Johannes P van Dijk ◽

Xi Long ◽

...

Keyword(s):

Status Epilepticus ◽

Brain Activity ◽

Automated Analysis ◽

Kappa Statistics ◽

Convulsive Status Epilepticus ◽

Eeg Analysis ◽

Gradual Onset ◽

Movement Artifacts ◽

Eeg Recordings ◽

Interictal Discharges

AbstractObjectiveElectroencephalography (EEG) interpretations through visual (by human raters) and automated (by computer technology) analysis are still not reliable for the diagnosis of non-convulsive status epilepticus (NCSE). This study aimed to identify typical pitfalls in the EEG analysis and make suggestions as to how those pitfalls might be avoided.MethodsWe analyzed the EEG recordings of individuals who had clinically confirmed or suspected NCSE. Epileptiform EEG activity during seizures (ictal discharges) were visually analyzed by two independent raters. We investigated whether unreliable EEG visual interpretations quantified by low inter-rater agreement can be predicted by the characteristics of ictal discharges and individuals’ clinical data. In addition, the EEG recordings were automatically analyzed by in-house algorithms. To further explore the causes of unreliable EEG interpretations, two epileptologists analyzed EEG patterns most likely misinterpreted as ictal discharges based on the differences between the EEG interpretations through the visual and automated analysis.ResultsShort ictal discharges with a gradual onset (developing over 3 seconds in length) were liable to be misinterpreted. An extra 2 minutes of ictal discharges contributed to an increase in the kappa statistics of > 0.1. Other problems were the misinterpretation of abnormal background activity (slow wave activities, other abnormal brain activity, and the ictal-like movement artifacts), continuous interictal discharges, and continuous short ictal discharges.ConclusionA longer duration criterion for NCSE-EEGs than 10 seconds that commonly used in NCSE working criteria is needed. Using knowledge of historical EEGs, individualized algorithms, and context-dependent alarm thresholds may also avoid the pitfalls.

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