Spindle-like Activity Research Articles

Role of EEG spindle-like activity in post cardiac arrest prognostication

AimEEG is considered in guidelines for poor outcome prognostication in comatose patients after cardiac arrest (CA), but elements related to favorable prognosis have also been increasingly described. While spindle EEG activity is known to herald good outcome in critically ill patients, its occurrence in CA has received limited attention, essentially in pediatric cohorts. We postulated that this feature is related to favorable outcome in adults. MethodsRetrospective assessment of comatose adults following CA in a prospective institutional registry (09.2021–09.2023). Spindle-like activity, noted prospectively on early (12–36 h) and late (36–72 h) routine EEGs, was tested using 2x2 tables and comparisons of proportions for the likelihood of favorable outcome (CPC 1–2 at 3 months), including combinations with existing benign EEG descriptions (Westhall: no malignant or highly malignant features; modified: also allowing background discontinuity, low voltage, inverse development). Spindles were correlated with peak serum neuron-specific enolase (NSE) at 24–48 h as a marker of neuronal damage. ResultsAmong 276 patients, spindle-like activity was observed in 66 (23.9 %) of them, more often in early EEGs. While, in isolation, this feature detected within 72 h showed high specificity for CPC 1–2 (82.2 %) and low sensitivity (36.8 %), its addition significantly enhanced sensitivity of modified benign EEG (from 90.5 % to 95.8 %; p < 0.001; specificity at 54.4 %). Patients with spindle-like activity had significantly lower NSE (median 25.7µg/l, interquartile range 16.1–24.4, vs. 39.4 µg/l, interquartile range 21.1–95.1; p < 0.001). ConclusionSpindle-like EEG activity may orient on prognostication of favorable outcome in adult post CA patients, and correlates with lower neuronal damage.

0449 Characterizing Spindle Activity as a Time-Frequency Phenomenon

Abstract Introduction Spindles are currently defined clinically based on observed patterns in the EEG waveform trace, with automated methods seeking to replicate visual scoring by experts. Recent work suggests that sleep spindles may be more readily observed as time-frequency peaks in the EEG spectrogram. This study compares spectral peaks in the multitaper spectrogram to expert and automatic detection scoring, characterizes the variability of spindles across a night, and investigates topographical and temporal clustering of spindles within individual EEG records. Methods We compared spectral peaks, expert scoring, and automatic detection in two datasets (DREAMS, and a high-density control study). Peaks were identified using multitaper spectral estimation and the peak prominence of the normalized power spectrum for each channel. Spatiotemporal variability analysis was performed using cluster and pattern recognition algorithms including penalized sorting of channel activation order, 2D-cross correlation, PCA and UMAP cluster analysis, and the seqNMF method. Results Spectral peaks were shown to be highly robust to and easily differentiated from broadband noise, occuring at rates (10-16 per min) far exceeding spindle rates reported in literature (~2.5 per min). Expert scoring and automated scoring failed to capture clear spectral peaks in the time-frequency domain, indicating an underreporting of the phenomenology. No apparent clustering or patterns of sleep spindle-like activity was observed using the proposed methods, suggesting high variability of spatiotemporal evolution of spindles. Conclusion These results suggest that the difficulty of time-domain visual scoring of spindles causes an artificially low estimate of the underlying phenomenology, which is mirrored in the assumptions implicit in the thresholds of automated scorers. This work shows that spindles are highly variable in their spatiotemporal evolution, suggesting that there is no optimal single electrode for analysis and casting doubt on the presence of a single cortical generation mechanism. We must therefore revisit the concept of the spindle using the time-frequency domain to more robustly characterize underlying phenomenology. Support National Institute Of Neurological Disorders And Stroke Grant R01 NS-096177

The early electroclinical manifestations of infantile spasms: A video EEG study.

Purpose:Infantile spasms are described as flexor extensor and mixed; but more features of their semiology and ictal electroencephalography (EEG) changes are sparse in the literature. The purpose of the study was to describe the clinical and ictal video-EEG characteristics of consecutive cases with infantile spasms and to try to find an association with the etiology.Materials and Methods:The clinical phenomenology and EEG characteristics on video-EEG were analyzed in 16 babies with infantile spasms.Results:A total of 869 spasms were reviewed. Nine (56.3%) showed focal seizures at least once during the recording and 1 (6.3%) had multifocal myoclonus in addition to the spasms. The duration of the cluster and interval between spasms was totally variable in all patients. Lateralizing phenomena were present in at least some of the spasms in all patients. Unilateral manual automatism in the form of holding the pinna was noted in three patients following the spasm. The ictal EEG activity in the majority (75%) was the slow wave. Four (25%) showed fast generalized spindle-like ictal discharges. Spikes, spike and wave activity, or electrodecremental pattern alone during the ictus was seen in none. On bivariate analysis, no factor noted on the video EEG had association with the etiology.Conclusion:Infantile spasms could be associated with focal and other seizures, has unique, non-uniform and variable semiology from patient to patient. The ictal EEG manifestation in the majority (75%) of our patients was the slow wave transient with 25% showing generalized fast spindle-like activity.

Ictal electroencephalographic activity in West syndrome

Epileptic spasm in West syndrome (WS) have unique clinical and EEG pattern. Usually ictal EEG shows high voltage slow wave during epileptic spasms or superimposed spindle-like fast activity of medium amplitude and a decremental activity. The spindle-like activity occurred either isolated, generally at the beginning or the end of a cluster or immediately before the slow wave. The decremental activity, correspond to a post ictal pattern following the slow waves. We selected EEGs od 25 infants having WS, followed for at least 10 years. Symmetric spasms were present in cryptogenic and symptomatic patients. Asymmetric spasms, and/or focal signs during spasms, strongly indicated existence of a cerebral lesion. In both etiological groups, the characteristic ictal EEG pattern of the spasms consisted of a positive-vertex slow wave. Fast activity (spindle-like), and decremental activity were also present. The consistent lateralization of the ictal EEG events correlated with EEG beta-activity. We considered it as indicating local cortical dysfunction in infants who fail to respond to early treatment and often progress toward severe epilepsy. Although independent from the etiology of the spasms, persisting hypsarrhythmia during a cluster of spasms appeared as an EEG pattern that correlated with a favorable outcome.

Enhanced automated sleep spindle detection algorithm based on synchrosqueezing.

Detection of sleep spindles is of major importance in the field of sleep research. However, manual scoring of spindles on prolonged recordings is very laborious and time-consuming. In this paper, we introduce a new algorithm based on synchrosqueezing transform for detection of sleep spindles. Synchrosqueezing is a powerful time-frequency analysis tool that provides precise frequency representation of a multicomponent signal through mode decomposition. Subsequently, the proposed algorithm extracts and compares the basic features of a spindle-like activity with its surrounding, thus adapting to an expert's visual criteria for spindle scoring. The performance of the algorithm was assessed against the spindle scoring of one expert on continuous electroencephalogram sleep recordings from two subjects. Through appropriate choice of synchrosqueezing parameters, our proposed algorithm obtained a maximum sensitivity of 96.5% with 98.1% specificity. Compared to previously published works, our algorithm has shown improved performance by enhancing the quality of sleep spindle detection.

Correlations between adolescent processing speed and specific spindle frequencies.

Sleep spindles are waxing and waning thalamocortical oscillations with accepted frequencies of between 11 and 16 Hz and a minimum duration of 0.5 s. Our research has suggested that there is spindle activity in all of the sleep stages, and thus for the present analysis we examined the link between spindle activity (Stage 2, rapid eye movement (REM) and slow wave sleep (SWS)) and waking cognitive abilities in 32 healthy adolescents. After software was used to filter frequencies outside the desired range, slow spindles (11.00–13.50 Hz), fast spindles (13.51–16.00 Hz) and spindle-like activity (16.01–18.50 Hz) were observed in Stage 2, SWS and REM sleep. Our analysis suggests that these specific EEG frequencies were significantly related to processing speed, which is one of the subscales of the intelligence score, in adolescents. The relationship was prominent in SWS and REM sleep. Further, the spindle-like activity (16.01–18.50 Hz) that occurred during SWS was strongly related to processing speed. Results suggest that the ability of adolescents to respond to tasks in an accurate, efficient and timely manner is related to their sleep quality. These findings support earlier research reporting relationships between learning, learning potential and sleep spindle activity in adults and adolescents.

The Association between Intraoperative Electroencephalogram-Based Measures and Pain Severity in the Post-Anaesthesia Care Unit

This observational study aimed to identify simple electroencephalogram indices of inadequate intraoperative opioid-mediated nociceptive blockade and to compare these indices with routinely used clinical predictors of severe postoperative pain in adults. Intraoperative trend and waveform data (electrocardiogram, pulse oximetry and electroencephalogram) were collected, pain intensity in the post-anaesthesia care unit was quantified using an 11-point Verbal Rating Score, and opioid administration was recorded. Using the initial post-anaesthesia care unit Verbal Rating Score as the primary endpoint, the relationship between five possible explanatory variables--surgery type, depth of volatile anaesthesia (minimum alveolar concentration), electroencephalogram signs (state entropy, spindle-like activity and delta-band power) and estimated end-of-operation effect-site morphine concentrations--was examined. One hundred and thirteen patients were recruited, with 94 included in the final clinical and electroencephalogram data analysis. Fifty-two patients had moderate or severe pain (Verbal Rating Score > or = 5). State entropy was lower (46.5 +/- 2.9 vs 43.1 +/- 1.9, P = 0.04) and spindle-like activity higher (0.42 +/- 0.03 vs 0.50 +/- 0.02, P = 0.03) in the moderate/severe pain group. [corrected] These findings suggest that there is a modest association between electroencephalogram measures near the end of surgery and the severity of postoperative pain.

LAMINAR DISTRIBUTION OF GAP-JUNCTIONS IN RAT SOMATIC CORTICAL COLUMNS

Results about the spindle-like activity peculiarities and the dendro-dendritic gap-junctions numbers in the infragranular and supragranular layers (modules) of the rat somatic cortex columns are presented. During simultaneous recording of extracellular field potentials from the cortical columns, the following was revealed: (i) the spindle-like activity was more synchronized inside one cortical column than in different columns; (ii) in most of the experiments (9 out of 10) an amplitude of the spindle waves was two times more in the supragranular layers than in the infragranular layers. During electron microscopy investigation of the experimental objects used in the electrophysiological study, it was shown that the number of the gap-junctions was more in the supragranular columnar layers as compared with the infragranular layers (4.15% and 2.84% out of the total number of chemical synapses and gap-junctions identified in each module, respectively). The results obtained are discussed as possible structural base of the local electrotonic synchronization of the neuronal activity inside a cortical column.

Dreaming and Electroencephalographic Changes during Anesthesia Maintained with Propofol or Desflurane

Dream recall is reportedly more common after propofol than after volatile anesthesia, but this may be due to delayed emergence or more amnesia after longer-acting volatiles. The electroencephalographic signs of dreaming during anesthesia and the differences between propofol and desflurane also are unknown. The authors therefore compared dream recall after propofol- or desflurane-maintained anesthesia and analyzed electroencephalographic patterns in dreamers and nondreamers and in propofol and desflurane patients for similarities to rapid eye movement and non-rapid eye movement sleep. Three hundred patients presenting for noncardiac surgery were randomized to receive propofol- or desflurane-maintained anesthesia. The raw electroencephalogram was recorded from induction until patients were interviewed about dreaming when they became first oriented postoperatively. Using spectral and ordinal methods, the authors quantified the amount of sleep spindle-like activity and high-frequency power in the electroencephalogram. The incidence of dream recall was similar for propofol (27%) and desflurane (28%) patients. Times to interview were similar (median 20 [range 4-114] vs. 17 [7-86] min; P = 0.1029), but bispectral index values at interview were lower (85 [69-98] vs. 92 [40-98]; P < 0.0001) in propofol than in desflurane patients. During surgery, the raw electroencephalogram of propofol patients showed more and faster spindle activity than in desflurane patients (P < 0.001). The raw electroencephalogram of dreamers showed fewer spindles and more high-frequency power than in nondreamers in the 5 min before interview (P < 0.05). Anesthetic-related dreaming seems to occur just before awakening and is associated with a rapid eye movement-like electroencephalographic pattern.

All Together Now

All Together Now

Corticothalamic 5-9 Hz oscillations are more pro-epileptogenic than sleep spindles in rats.

Absence-related spike-and-wave discharges (SWDs) occur in the thalamocortical system during quiet wakefulness or drowsiness. In feline generalized penicillin epilepsy, SWDs develop from sleep spindles. In contrast, in genetic absence epilepsy rats from Strasbourg (GAERS), SWDs develop from wake-related 5-9 Hz oscillations, which are distinct from spindle oscillations (7-15 Hz). Since these two oscillation types share common frequency bands and may contribute to SWD genesis, it is important to compare their thalamic cellular mechanisms. Under neuroleptic analgesia, in GAERS and control non-epileptic rats barbiturates abolished both SWDs and 5-9 Hz oscillations but increased the incidence of spindle-like oscillations. Within the thalamocortical circuit 5-9 Hz oscillations occurred more coherently than spindle-like oscillations. Intracellular events associated with 5-9 Hz and spindle-like oscillations were distinctively different in both thalamic relay and reticular neurons. In both cell types, SWDs and 5-9 Hz oscillations emerged from a significantly more depolarized membrane potential than spindle-like oscillations. In relay neurons, 5-9 Hz oscillations were mainly characterized by a rhythmic depolarization, which occurred during a tonic hyperpolarization and which could trigger an apparent low-threshold Ca2+ potential, whereas spindle-like oscillations were characterized by a rhythmic hyperpolarization. In reticular cells, SWDs and 5-9 Hz oscillations occurred during a tonic hyperpolarization, whereas spindle-like oscillations occurred during a long-lasting depolarizing envelope. The difference in the intracellular events between 5-9 Hz and spindle-like oscillations and similarities between 5-9 Hz oscillations and SWDs indicate that in GAERS, 5-9 Hz oscillations are more pro-epileptogenic than spindle-like oscillations. In conclusion, the present study strongly supports the hypothesis that SWDs in GAERS are generated by a wake-related corticothalamic resonance, and not by sleep-related, hypersynchronous, spindle-like activity originating in the thalamus.

Thalamocortical connectivity in a rat brain slice preparation: participation of the ventrobasal complex to synchronous activities

We studied the synchronous cortical and thalamic activities induced by low (0.5–1 mM) and high (50–100 mM) concentrations of the K+ channel blocker 4-aminopyridine (4AP) in a rat thalamocortical preparation. The presence of reciprocal thalamocortical connectivity was documented by diffusion of the fluorescent tracer Di-IC18 between the somatosensory cortex and the ventrobasal complex (VB) of the thalamus in vitro. Functional reciprocal connectivity was also demonstrated by stimulating the cortical middle-deep layers (which elicited orthodromic responses in VB) or the VB (which induced orthodromic and antidromic responses in the cortex). Spontaneous field potentials were not recorded in either the thalamus or cortex in control medium. Low concentrations of 4AP produced local spindle-like rhythmic oscillations in cortex and VB (duration = 0.4–3.5 s; frequency = 9–16 Hz). In contrast, high concentrations of 4AP induced widespread ictal-like epileptiform discharges (duration = 8–45 s) characterised by lsquo ‘tonic’ component followed by a period of ‘clonic’ discharges in both cortex and VB. Spindle-like activity was abolished in cortex and thalamus by applying the excitatory amino acid receptor antagonist kynurenic acid in VB. In contrast, the same procedure exacerbated ictal-like discharges, while depressing VB activity. Our results indicate that thalamus and cortex can produce synchronous activities in this in vitro thalamocortical network: spindle-like rhythmic oscillations are generated at the thalamic level and imposed upon the cortical network whereas ictal-like discharges have a cortical origin and are modulated by the thalamic network activity. In addition, we have shown that it is possible to preserve reciprocal projections between cortex and thalamus in an in vitro rat slice preparation that could be a valuable tool to study epileptic-prone rat strains.

Thalamocortical connectivity in a rat brain slice preparation: participation of the ventrobasal complex to synchronous activities

We studied the synchronous cortical and thalamic activities induced by low (0.5–1 mM) and high (50–100 mM) concentrations of the K + channel blocker 4-aminopyridine (4AP) in a rat thalamocortical preparation. The presence of reciprocal thalamocortical connectivity was documented by diffusion of the fluorescent tracer Di-IC 18 between the somatosensory cortex and the ventrobasal complex (VB) of the thalamus in vitro. Functional reciprocal connectivity was also demonstrated by stimulating the cortical middle-deep layers (which elicited orthodromic responses in VB) or the VB (which induced orthodromic and antidromic responses in the cortex). Spontaneous field potentials were not recorded in either the thalamus or cortex in control medium. Low concentrations of 4AP produced local spindle-like rhythmic oscillations in cortex and VB (duration=0.4–3.5 s; frequency=9–16 Hz). In contrast, high concentrations of 4AP induced widespread ictal-like epileptiform discharges (duration=8–45 s) characterised by a ‘tonic’ component followed by a period of ‘clonic’ discharges in both cortex and VB. Spindle-like activity was abolished in cortex and thalamus by applying the excitatory amino acid receptor antagonist kynurenic acid in VB. In contrast, the same procedure exacerbated ictal-like discharges, while depressing VB activity. Our results indicate that thalamus and cortex can produce synchronous activities in this in vitro thalamocortical network: spindle-like rhythmic oscillations are generated at the thalamic level and imposed upon the cortical network whereas ictal-like discharges have a cortical origin and are modulated by the thalamic network activity. In addition, we have shown that it is possible to preserve reciprocal projections between cortex and thalamus in an in vitro rat slice preparation that could be a valuable tool to study epileptic-prone rat strains.

The activity of thalamus and cerebral cortex neurons in rabbits during "slow wave-spindle" EEG complexes.

"Slow wave-spindle" complexes were studied during slow wave sleep in rabbits at the thalamic (medial thalamus) and cortical (upper and lower layers of the sensorimotor cortex) levels. Slow wave complexes are biphasic positive-negative complexes or triphasic complexes with a predominantly negative component. Spindles have characteristics close to those of spontaneous sleep spindles. Complexes arise singly, as though inserted into the rhythm of spontaneous sleep spindles, or in series with periods similar to the spindle rhythm. Medial thalamus neurons and some cortical neurons had the same activity during waves as during spindles: if the neuron decreased (increased) its spike frequency in a spindle, then decreases (increases) in frequency were also seen in slow waves; if the neuron produced trains of discharges during spindles, then trains of activity were also seen from the slow-wave part of "slow wave-spindle" complexes. The membrane potential changed in a similar fashion: on a background of hyperpolarization which started at the slow wave, individual depolarization oscillations appeared in the EEG wave rhythm; these oscillations were not always accompanied by spike trains. The slow wave mechanism, the rhythms of isolated complexes and simultaneous complexes and spontaneous sleep spindles may share a common underlying mechanism: slow, cyclical variations in excitability in thalamocortical neuronal networks, which have previously been demonstrated for spindle-like activity. The possibility that there are common mechanisms for slow waves in complexes and other EEG slow waves, particularly delta activity, remains hypothetical.

Diffuse Theta Activity and Spindle-Like Bursts during Coma after Cardiac Arrest

An usual combination of diffuse theta activity with intermittent bursts of spindle-like activity, followed by 2-3 Hz rhythmic discharges and lasting about 7 seconds, was noted in a coma patient after cardiac arrest. We speculate that the theta pattern coma and spindle-like bursts originated in the pontine region, and that those bursts in turn triggered or recruited rhythmic slow-wave complexes similar to absence discharges.

Changes in electric activity (EEG) of the telencephalon of conscious toads ( Bufo paracnemis) caused by cholinergic stimulation of the mesencephalic tegmentum

Studies were carried out to investigate the effect of microinjection of cholinergic agonist carbamylcholine (carbachol) into the mesencephalic tegmentum of conscious toads ( Bufo paracnemis), subjected or not to section of the olfactory nerves, on the electrical activity (EEG) of the telencephalon. The response depended on the type of preexisting EEG activity. Marked desynchronization was observed both in animals with intact nerves and in animals with sectioned nerves, whose previous basal activity was already desynchronized (high frequency and low amplitude). In toads with synchronized basal activity and with intact nerves, an increase, a fall or even abolition of preexisting spindle-like activity occurred, whereas in animals with sectioned nerves the effect was reduction or abolition of spindle-like activity. The data show that stimulation of the mesencephalic tegmentum can alter the electrical activity of the telencephalon and that this effect is not only secondary to a change in nasal air flow alterations since it occurs in toads with sectioned olfactory nerves.

Formation of "caudate spindles" in the rabbit sensomotor cortex during ontogeny

Electrical activity of the sensomotor and visual areas of the neocortex during stimulation of the caudate nucleus was recorded in young rabbits aged 3–60 days and in adults. Single stimulation of the caudate nucleus was found to cause the appearance of characteristic bursts of spindle-like rhythmic activity ("caudate spindles"), described previously in cats and monkeys, in the adult rabbit cortex. The latent period of the caudate spindle was about 200 msec, its duration 1–3 sec, and the frequency of its oscillations of the order of 12 Hz. Caudate spindles were most marked in the sensomotor cortex of the ipsilateral hemisphere. In rabbits under 10 days old caudate spindles were not found even if the intensity of stimulation was increased many times. Starting from the age of 15 days bursts of rhythmic activity resembling caudate spindles, but with lower frequency (about 8 Hz), longer latent period (up to 350 msec), and also with a higher threshold, appeared in the sensomotor cortex. The definitive type of caudate spindles was established toward the end of the first month of postnatal life, corresponding to the time of formation and complication of conditioned-reflex activity in developing animals.

Rhythmic activity of the brain evoked by local injections of carbachol into subcortical nuclei.

The effect of local injections of carbachol into the caudate nucleus and individual nuclei of the thalamus on the electrocorticogram of the anterior portion of the brain was investigated in unanesthetized, immobilized cats. It was shown that chemical stimulation of subcortical structures, like electrical stimulation, can induce spindle-like activity and a recruitment response. The appearance of these reactions after injections of carbachol both into the caudate nucleus and into individual nuclei of the thalamus indicates the existence of a functionally unified caudate-thalamic cholinoreceptive system, responsible for the slow wave rhythmic activity.

Spindlelike cortical potentials during postnatal development of rabbits.

The development of the total cortical potentials was investigated in rabbits from the 3rd to the 41st day of postnatal development. It is shown that in newborn rabbits periodic spindlelike outbursts of high-amplitude potentials are a characteristic manifestation of its primary activity. This form of activity is observed both in a resting state and during movements of the animal. After the bunny opens its eyes, especially beginning with the 16th day of development, periodic outbursts of high-amplitude potentials are observed only during behavioral signs of sleep or under conditions of nembutal narcosis. The parameters of the periodicity and frequency composition of the outbursts do not undergo substantial changes during maturation of the cortex. Apparently the “sleep spindles” of the mature brain are genetically related to the primary spindlelike activity of the immature cortex and have the same mechanism as the primary spindles of the immature cortex.

Spindle-like activity appearing during paradoxical sleep in rats with iron-induced cortical focus.

Under barbiturate anesthesia, male Wistar rats weighing 250-300 g were injected with 2.5 microliters of 0.2 M FeCl3 solution into the left sensori-motor cortex to induce an epileptic focus with minimal abnormal activities. Polygraphy started 1 week after the surgery, showed a spindle-like hypersynchronous activity that appeared not only in the slow wave sleep period but also during paradoxical sleep (PS). This activity had a frequency of 8-14 Hz. The amplitude was more than 200 mu v in the right (non-injected side) cortex but very small in the left cortex (injected side). Isolated spike discharges were observed in an ECoG of slow wave sleep. Apart from this activity there was nothing resembling the usual sleep spindles.