Slow Wave Amplitude Research Articles

Intracranial pressure variability: relation to clinical outcome, intracranial pressure\u2013volume index, cerebrovascular reactivity and blood pressure variability

It was recently found in traumatic brain injury (TBI) that ICP variability (ICPV) predicted favorable outcome. We hypothesized that ICPV may depend on intracranial compliance, unstable blood pressure and cerebral vasomotion. In this study, we aimed to further investigate the explanatory variables for ICPV and its relation to outcome. Data from 362 TBI patients were retrospectively analyzed day 2 to 5 post-injury. ICPV was evaluated in three ways. First, variability in the sub-minute time interval (similar to B waves) was calculated as the amplitude of the ICP slow waves using a bandpass filter, limiting the analysis to oscillations of 55 to 15 s (ICP AMP 55–15). The second and third ICPV measures were calculated as the deviation from the mean ICP averaged over 30 min (ICPV-30m) and 4 h (ICPV-4h), respectively. All ICPV measures were associated with a reduced intracranial pressure/volume state (high ICP and RAP) and high blood pressure variability in multiple linear regression analyses. Higher ICPV was associated with better pressure reactivity in the univariate, but not the multiple analyses. All ICPV measures were associated with favorable outcome in univariate analysis, but only ICP AMP 55–15 and ICPV-30m did so in the multiple logistic regression analysis. Higher ICPV can be explained by a reduced intracranial compliance and variations in cerebral blood volume due to the vessel response to unstable blood pressure. As ICP AMP 55–15 and ICPV-30m independently predicted favorable outcome, it may represent general cerebral vessel activity, associated with better cerebral blood flow regulation and less secondary insults.

Independent ERP predictors of affective priming underline the importance of depth of prime and target processing and implicit affect misattribution

We used event-related potentials (ERPs) to investigate the mental processes that contribute to affective priming (AP), a systematic shift of evaluative judgments about neutral targets toward the valence of preceding primes. 64 participants rated their liking of a priori neutral ideographs preceded by 800-ms emotional primewords, while 64-channel EEG was recorded. We observed a significant AP effect that was closely associated with prime valence dependent variations of the right central-to-parieto-occipital positive slow wave (PSW) amplitude in the target ERP, providing evidence for implicit affect misattribution as one source of the effect. While deeper target processing mirrored in valence unspecific central-to-parieto-occipital target PSW amplitude was negatively associated with AP, deeper prime processing indicated by valence unspecific central-to-parieto-occipital prime PSW amplitude was positively related to AP. These depth of processing effects underline the importance of strategic processes in AP. In a stepwise linear regression analysis, the prime valence effect on right central-to-parieto-occipital target PSW indicating affect misattribution and the two valence-unspecific ERP indices of processing depth (central-to-parieto-occipital prime- and target PSW) were independent predictors of the size of the AP effect. Together they accounted for 60% of the variance. Furthermore, an explorative analysis provided first evidence for the relevance of early discrimination of prime valence for AP.

Infraslow coordination of slow wave activity through altered neuronal synchrony.

Slow wave activity (SWA; the EEG power between 0.5 and 4 Hz during non-rapid eye movement sleep [NREM]) is the best electrophysiological marker of sleep need; SWA dissipates across the night and increases following sleep deprivation. In addition to these well-documented homeostatic SWA trends, SWA exhibits extensive variability across shorter timescales (seconds to minutes) and between local cortical regions. The physiological underpinnings of SWA variability, however, remain poorly characterized. In male Sprague-Dawley rats, we observed that SWA exhibits pronounced infraslow fluctuations (~40- to 120-s periods) that are coordinated across disparate cortical locations. Peaks in SWA across infraslow cycles were associated with increased slope, amplitude, and duration of individual slow waves and a reduction in the total number of waves and proportion of multipeak waves. Using a freely available data set comprised of extracellular unit recordings during consolidated NREM episodes in male Long-Evans rats, we further show that infraslow SWA does not appear to arise as a consequence of firing rate modulation of putative excitatory or inhibitory neurons. Instead, infraslow SWA was associated with alterations in neuronal synchrony surrounding "On"/"Off" periods and changes in the number and duration of "Off" periods. Collectively, these data provide a mechanism by which SWA can be coordinated across disparate cortical locations and thereby connect local and global expression of this patterned neuronal activity. In doing so, infraslow SWA may contribute to the regulation of cortical circuits during sleep and thereby play a critical role in sleep function.

Effects of Nitric Oxide on Slow Waves and Spontaneous Contraction of Guinea Pig Gastric Antral Circular Muscle

We examined the effects of nitric oxide (NO) donors, S-nitroso-L-cysteine (Cys-NO) and 3-morpholinosydnonimine hydrochloride (SIN-1), on slow waves and contractile activity in the circular muscle of guinea pig gastric antrum. In the presence of atropine and guanethidine, electrical field stimulation (EFS) reduced the amplitude of phasic contraction. The effect of EFS was significantly inhibited by both the NO synthase inhibitor Nω-nitro-L-arginine methyl ester and a soluble guanylate cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ). Cys-NO and SIN-1 mimicked the effect of EFS on phasic contraction and reduced the amplitude of slow waves in a concentration-dependent manner, with no effect on frequency and resting membrane potential. Phasic contraction was more sensitive to NO donors than slow waves. The inhibitory effects of NO donors were antagonized by ODQ and mimicked by a membrane permeable cGMP analogue 8-bromo-cGMP. Several K+ channel blockers such as apamin, iberiotoxin, and glibenclamide had no effect on the inhibitory action of SIN-1. These results suggest that NO inhibits the phasic contraction and slow waves through cGMP-dependent mechanisms in guinea pig gastric antrum. The effect of NO is unlikely to be mediated by the activation of Ca2+-activated or ATP-sensitive K+ channels.

Feasibility of High-Resolution Electrical Mapping for Characterizing Conduction Blocks Created by Gastric Ablation.

The interstitial cells of Cajal (ICC) initiate, coordinate and propagate bioelectrical slow wave activity that drives gastric motility. In the healthy human stomach, slow wave activity is highly organized. Gastric motility disorders are associated with dysrhythmias. While ablation is widely used to treat cardiac dysrhythmias, this approach has yet to be trialed in the stomach. In this study, radiofrequency (RF) ablation was applied in pig stomachs in vivo to create targeted electrical conduction blocks. Ablations were performed at temperature control mode (55-70°C), and resultant conduction blocks were identified and verified using high-resolution electrical mapping. Termination of slow wave propagation at ablation sites was confirmed by a decrease in extracellular slow wave amplitude from 1.7 ± 0.2 mV to an undetectable amplitude, as well as spatiotemporal pattern analysis of conduction blocks. The use of high-resolution electrical mapping can now be employed to investigate ablation as a potential therapy for gastric dysrhythmias in motility disorders.

The role of sleep-related cognitive functions in the spectrum of benign epilepsy with centro-temporal spikes.

Heterogeneous cognitive deficits have been described in the spectrum of benign epilepsy with centro-temporal spikes, which strongly correlate with the intensity of interictal epileptiform discharges and its spreading, in particular during sleep, mostly within the perisylvian cognitive network. The aim of this review is to discuss current findings regarding the connection between sleep alterations and cognitive function in the spectrum of benign epilepsy with centro-temporal spikes. A longer sleep onset latency is the only evident sleep macrostructure alteration reported in the spectrum of benign epilepsy with centro-temporal spikes. On a microstructural level, a higher spike count of descending compared to ascending slopes of sleep cycles, an impairment of slow wave downscaling, and amplitude and slope of slow waves were found in the spectrum of benign epilepsy with centro-temporal spikes. Moreover, children with benign epilepsy with centro-temporal spikes had a reduced non-rapid eye movement sleep instability, in terms of cyclic alternating pattern, similar to that found in children with attention-deficit hyperactivity disorders and in children with obstructive sleep apnea and centro-temporal spike during sleep. Children with benign epilepsy with centro-temporal spikes have a known comorbidity with attention-deficit hyperactivity disorders and obstructive sleep apnea.Conclusion: Considering the common sleep microstructure alterations, the presence of attention deficit and hyperactivity and/or sleep apnea may be a considered warning sign in the case of benign epilepsy with centro-temporal spikes. What is Known: • Sleep related-cognitive deficits have been described in the spectrum of benign epilepsy with centro-temporal spikes. The degree of sleep alterations may predict the neurocognitive outcome, and help clinicians to choose the right treatment. What is New: • Considering the common sleep microstructure alterations, attention deficit and sleep apnea, may be a considered warning signs.

High-resolution Mapping of Hyperglycemia-induced Gastric Slow Wave Dysrhythmias.

Background/AimsIt is now recognised that gastric dysrhythmias are best characterised by their spatial propagation pattern. Hyperglycemia is an important cause of gastric slow wave dysrhythmia, however, the spatiotemporal patterns of dysrhythmias in this context have not been investigated. This study aims to investigate the relationship between hyperglycemia and the patterns of dysrhythmias by employing high-resolution (multi-electrode) mapping simultaneously at the anterior and posterior gastric serosa.MethodsHigh-resolution mapping (8 × 16 electrodes per serosal) was performed in 4 anesthetized hounds. Baseline recordings (21 ± 8 minutes) were followed by intravenous injection of glucagon (0.5 mg per dose) and further recordings (59 ± 15 minutes). Blood glucose levels were monitored manually using a glucose sensing kit at regular 5-minute intervals. Slow wave activation maps, amplitudes, velocity, anisotropic ratio, and frequency were calculated. Differences were compared between baseline and post glucagon injection.ResultsBaseline slow waves propagated symmetrically and antegrade. The blood glucose levels were increased by an average of 112% compared to the baseline by the end of the recordings. All subjects demonstrated elevated incidence of slow wave dysrhythmias following injection compared to the baseline (48 ± 23% vs 6 ± 4%, P < 0.05). Dysrhythmias arose simultaneously or independently on anterior and posterior serosa. Spatial dysrhythmias occurred before and persisted after the onset and disappearance of temporal dysrhythmias.ConclusionsInfusion of glucagon induced gastric slow wave dysrhythmias, which occurred across a heterogeneous range of patterns and frequencies. The spatial dysrhythmias of gastric slow waves were shown to be more prevalent and persisted over a longer period of time compared to the temporal dysrhythmias.

Individual slow-wave morphology is a marker of aging

Slow-wave activity is a hallmark of deep non-rapid eye movement sleep. Scalp slow wave morphology is stereotypical and it is highly correlated with the synchronized onset and cessation of cortical neuronal firing measured from the surface or depth of the cortex. It is also strongly affected by aging, and these changes are causally associated with age-related cognitive decline. We investigated how normal aging affects the individual morphology of the slow wave and whether these changes are captured by the summary slow wave parameters generally used in the literature. We recorded full-night polysomnography in 176 participants (age 17–69 years) and automatically detected slow waves. We established individual slow morphologies using average amplitude at 501 data points for each participant and also calculated the individual average slow-wave amplitude, average ascending and descending slope steepness, halfwave duration, and the total number of slow waves (gross parameters). Using least absolute shrinkage and selection operator penalized regression, we found that SW gross parameters explain up to 60% of age variance but using fine morphology up to 80% of age variance can be accounted for. This predictive power was greatest when data from multiple channels were averaged, in midline derivations and in the first quarter of the night. Young participants had faster slow-wave polarity reversals, suggesting a more efficient initiation and termination of slow-wave downstate and upstate. Our results demonstrate the superiority of the high-resolution slow wave morphology as a biomarker of aging and highlight downstate-upstate transitions as promising targets of restorative stimulation-based interventions.

Neurophysiology of Avian Sleep: Comparing Natural Sleep and Isoflurane Anesthesia.

Propagating slow-waves in electroencephalogram (EEG) or local field potential (LFP) recordings occur during non-rapid eye-movement (NREM) sleep in both mammals and birds. Moreover, in both, input from the thalamus is thought to contribute to the genesis of NREM sleep slow-waves. Interestingly, the general features of slow-waves are also found under isoflurane anesthesia. However, it is unclear to what extent these slow-waves reflect the same processes as those giving rise to NREM sleep slow-waves. Similar slow-wave spatio-temporal properties during NREM sleep and isoflurane anesthesia would suggest that both types of slow-waves are based on related processes. We used a 32-channel silicon probe connected to a transmitter to make intra-cortical recordings of the visual hyperpallium in naturally sleeping and isoflurane anesthetized pigeons (Columba livia) using a within-bird design. Under anesthesia, the amplitude of LFP slow-waves was higher when compared to NREM sleep. Spectral power density across all frequencies (1.5–100 Hz) was also elevated. In addition, slow-wave coherence between electrode sites was higher under anesthesia, indicating higher synchrony when compared to NREM sleep. Nonetheless, the spatial distribution of slow-waves under anesthesia was more comparable to NREM sleep than to wake or REM sleep. Similar to NREM sleep, slow-wave propagation under anesthesia mainly occurred in the thalamic input layers of the hyperpallium, regions which also showed the greatest slow-wave power during both recording conditions. This suggests that the thalamus could be involved in the genesis of slow-waves under both conditions. Taken together, although slow-waves under isoflurane anesthesia are stronger, they share spatio-temporal activity characteristics with slow-waves during NREM sleep.

Layers of latent effects in cognitive control: An EEG investigation

Recent research demonstrates that two components of reaching behavior – initiation time (the time elapsed from stimulus presentation to movement initiation) and reach curvature (the degree to which a reach movement deviates from a direct path to the selected response) – exhibit distinct cross-trial dynamics in cognitive control tasks, indicating that these components of behavior reflect two dissociable processes underlying cognitive control: a threshold adjustment process involving the inhibition of motor output and a controlled selection process involving the recruitment of top-down resources to support goal-relevant behavior. The current study investigates the extent to which the cross-trial dynamics previously observed in reaching behavior in the Eriksen flanker task are reflected in event-related potentials during standard button-press responses. Candidate EEG measures of the threshold adjustment process (N2 and Pre-LRP amplitudes) failed to reveal the cross-trial dynamics previously observed in initiation times. Slow wave amplitudes exhibited a close correspondence to the cross-trial dynamics observed in reach curvatures, indicating that the measure is sensitive to some functions of the controlled selection process. Further, LRP slopes presented a close correspondence to the cross-trial dynamics observed in response times, indicating that this measure reflects the combined output of the threshold adjustment process and controlled selection process. The implications of these findings for future research examining the links among behavioral and neural dynamics are discussed.

Cortical zeta-inhibitory peptide injection reduces local sleep need.

Local sleep need within cortical circuits exhibits extensive interregional variability and appears to increase following learning during preceding waking. Although the biological mechanisms responsible for generating sleep need are unclear, this local variability could arise as a consequence of wake-dependent synaptic plasticity. To test whether cortical synaptic strength is a proximate driver of sleep homeostasis, we developed a novel experimental approach to alter local sleep need. One hour prior to light onset, we injected zeta-inhibitory peptide (ZIP), a pharmacological antagonist of protein kinase Mζ, which can produce pronounced synaptic depotentiation, into the right motor cortex of freely behaving rats. When compared with saline control, ZIP selectively reduced slow-wave activity (SWA; the best electrophysiological marker of sleep need) within the injected motor cortex without affecting SWA in a distal cortical site. This local reduction in SWA was associated with a significant reduction in the slope and amplitude of individual slow waves. Local ZIP injection did not significantly alter the amount of time spent in each behavioral state, locomotor activity, or EEG/LFP power during waking or REM sleep. Thus, local ZIP injection selectively produced a local reduction in sleep need; synaptic strength, therefore, may play a causal role in generating local homeostatic sleep need within the cortex.

The Role of Prostaglandins in Disrupted Gastric Motor Activity Associated With Type 2 Diabetes.

Patients with diabetes often develop gastrointestinal motor problems, including gastroparesis. Previous studies have suggested this gastric motor disorder was a consequence of an enteric neuropathy. Disruptions in interstitial cells of Cajal (ICC) have also been reported. A thorough examination of functional changes in gastric motor activity during diabetes has not yet been performed. We comprehensively examined the gastric antrums of Lepob mice using functional, morphological, and molecular techniques to determine the pathophysiological consequences in this type 2 diabetic animal model. Video analysis and isometric force measurements revealed higher frequency and less robust antral contractions in Lepob mice compared with controls. Electrical pacemaker activity was reduced in amplitude and increased in frequency. Populations of enteric neurons, ICC, and platelet-derived growth factor receptor α+ cells were unchanged. Analysis of components of the prostaglandin pathway revealed upregulation of multiple enzymes and receptors. Prostaglandin-endoperoxide synthase-2 inhibition increased slow wave amplitudes and reduced frequency of diabetic antrums. In conclusion, gastric pacemaker and contractile activity is disordered in type 2 diabetic mice, and this appears to be a consequence of excessive prostaglandin signaling. Inhibition of prostaglandin synthesis may provide a novel treatment for diabetic gastric motility disorders.

Effects of acute psychosocial stress on the neural correlates of episodic encoding: Item versus associative memory.

Acute stress is known to modulate episodic memory, but little is known about the extent to, and the circumstances under, which stress affects encoding of item vs. inter-item associative information for words of different valences. Furthermore, the precise neuro-cognitive mechanisms underlying stress effects on episodic encoding in humans are largely unknown. To address these questions, in the present study we recorded EEG activity while male participants encoded neutral, negative and positive words, each paired with another word that was always neutral. Immediately before encoding, half of the participants experienced a psychosocial stressor, the Trier Social Stress Test, while the other half underwent a control procedure. Twenty-four hours later, participants completed separate item and associative recognition tests. Pre-learning stress enhanced item recognition accuracy for the positive, but not for the negative words. By contrast, there was no evidence for stress effects on associative recognition. The increase in item recognition was accompanied by a higher familiarity-, but not recollection-, based item retrieval of positive and neutral, but not negative words. Crucially, in the event-related potential (ERP) stress affected the amplitude of the frontal slow wave in general, and the frontal slow wave subsequent memory effect for positive words in specific, and the subsequent memory effect was correlated with cortisol levels after the stress manipulation. Our results suggest that positive words are encoded more elaboratively under stress, leading to a higher likelihood of subsequent item retrieval. An interaction of cortisol with frontal-lobe dependent control processes as well as a shift in attentional biases may contribute to this stress-induced modulation of episodic encoding.

Reduced frontal slow wave density during sleep in first-episode psychosis

BackgroundSleep disturbances are commonly reported in psychotic patients and often contribute to the manifestation and severity of their symptoms. Slow waves characterize the deepest stage of NREM sleep, and their occurrence is critical for restorative sleep. Slow wave abnormalities have been reported in patient with schizophrenia, especially when experiencing an exacerbation of psychosis. However, their presence and delineation, with an emphasis on topography, in first-episode psychosis patients (FEP) have not yet been characterized. MethodsWe performed sleep high density (hd)-EEG recordings in twenty FEP patients and twenty healthy control subjects (HC). Slow wave activity (SWA) and several other slow wave parameters, e.g. density, amplitude, up- and down-slopes, were calculated at each electrode location and compared across groups. Additionally, the association between slow wave characteristics and clinical symptoms was assessed. ResultsFEP patients showed a reduction selectively in slow-wave density relative to HC, and this reduction was significant in a large frontal area, including channels overlying the prefrontal cortex. Furthermore, slow wave density was inversely correlated with the severity of FEP positive symptoms. ConclusionsAbnormalities in slow waves are present at the beginning of psychosis, occur in frontal-prefrontal regions that are highly dysfunctional in psychotic patients, and are associated with their positive symptom severity. Building on these findings, future work will help establish the direction of these associations (i.e., if clinical symptoms precede, coincide, or follow SW deficits), which will determine whether ameliorating slow wave sleep deficits is a viable treatment target in early psychosis.

NREM sleep EEG slow waves in autistic and typically developing children: Morphological characteristics and scalp distribution.

Autism is a developmental disorder with a neurobiological aetiology. Studies of the autistic brain identified atypical developmental trajectories that may lead to an impaired capacity to modulate electroencephalogram activity during sleep. We assessed the topography and characteristics of non-rapid eye movement sleep electroencephalogram slow waves in 26 boys aged between 6 and 13 years old: 13 with an autism spectrum disorder and 13 typically developing. None of the participants was medicated, intellectually disabled, reported poor sleep, or suffered from medical co-morbidities. Results are derived from a second consecutive night of polysomnography in a sleep laboratory. Slow waves (0.3-4.0 Hz; >75 µV) were automatically detected on artefact-free sections of non-rapid eye movement sleep along the anteroposterior axis in frontal, central, parietal and occipital derivations. Slow wave density (number per minute), amplitude (µV), slope (µV s-1 ) and duration (s) were computed for the first four non-rapid eye movement periods. Slow wave characteristics comparisons between groups, derivations and non-rapid eye movement periods were assessed with three-way mixed ANOVAs. Slow wave density, amplitude, slope and duration were higher in anterior compared with most posterior derivations in both groups. Children with autism spectrum disorder showed lower differences in slow waves between recording sites along the anteroposterior axis than typically developing children. These group differences in the topography of slow wave characteristics were stable across the night. We propose that slow waves during non-rapid eye movement sleep could be an electrophysiological marker of the deviant cortical maturation in autism linked to an atypical functioning of thalamo-cortical networks.

Compression waves in porous media containing gas hydrate

Wave processes in a porous medium containing water, gas and gas hydrate are numerically investigated. The two-velocity model of porous medium is used. The nonlinearity of the oscillations of the bubbles is taken into account in the equation of gas state and the equation for bubble radius. The transmission of compression of step waves from the water into hydrate-containing porous medium is investigated. Beyond the line of phase equilibrium the association of gas hydrate is possible. The influence of the medium parameters and the intensity of the incident wave on the evolution of waves in this porous medium is studied. When entering the porous medium, the initial pulse is divided into fast (deformation) and slow (filtration) waves. In a slow wave damped oscillations associated with pulsations of bubbles are observed. The increase in the initial equilibrium pressure in the medium leads to an increase in the velocities of the deformation and filtration waves. With the initial volume content of the gas in the pore space unchanged, an increase in the initial hydrate content leads to a small increase in the velocities and amplitudes of fast and slow waves. At constant initial volume content of hydrate, the increase of gas content leads to a noticeable decrease of slow wave speed and decrease of amplitudes of both fast and slow waves. It was found that the accounting of the processes of formation of gas hydrate in a porous medium at the considered time intervals does not have a noticeable effect on the character of wave propagation.

How do children fall asleep? A high-density EEG study of slow waves in the transition from wake to sleep

IntroductionSlow waves, the hallmarks of non-rapid eye-movement (NREM) sleep, are thought to reflect maturational changes that occur in the cerebral cortex throughout childhood and adolescence. Recent work in adults has revealed evidence for two distinct synchronization processes involved in the generation of slow waves, which sequentially come into play in the transition to sleep. In order to understand how these two processes are affected by developmental changes, we compared slow waves between children and young adults in the falling asleep period. MethodsThe sleep onset period (starting 30s before end of alpha activity and ending at the first slow wave sequence) was extracted from 72 sleep onset high-density EEG recordings (128 electrodes) of 49 healthy subjects (age 8–25). Using an automatic slow wave detection algorithm, the number, amplitude and slope of slow waves were analyzed and compared between children (age 8–11) and young adults (age 20–25). ResultsSlow wave number and amplitude increased linearly in the falling asleep period in children, while in young adults, isolated high-amplitude slow waves (type I) dominated initially and numerous smaller slow waves (type II) with progressively increasing amplitude occurred later. Compared to young adults, children displayed faster increases in slow wave amplitude and number across the falling asleep period in central and posterior brain regions, respectively, and also showed larger slow waves during wakefulness immediately prior to sleep. ConclusionsChildren do not display the two temporally dissociated slow wave synchronization processes in the falling asleep period observed in adults, suggesting that maturational factors underlie the temporal segregation of these two processes. Our findings provide novel perspectives for studying how sleep-related behaviors and dreaming differ between children and adults.

0336 Optimal Phase of Slow Wave Auditory Stimulation

Auditory closed loop stimulation as a non-pharmacological method for enhancement of slow wave sleep (SWS) has been proven effective. This work focuses on a key parameter of this methodology: the precise phase of delivery of the auditory pulse. Data from a set of 10 subjects were obtained overnight using a single electrode (frontal region) EEG device (Deepwave Cogniband). A Phase Locked Loop (PLL) algorithm tracked the slow waves (SW) identifying specific auditory stimulation target phases. The phase periodically changed (every 30 seconds) over a set of 6 preselected target phases during a single night of sleep. Data was filtered in the delta band range (0.5–4 Hz). Percent difference of the root mean square of the EEG amplitude between consecutive stimulation segments (lasting 5 PLL oscillations) and segments of sham data was calculated offline. We produced a circular diagram with each single block-pair (on and off) for each subject and the entire subject group as a function of EEG slow wave phase to study the function of phase in the stimulation procedure. We found an optimal range of phases around the angle 340 (+- 20 degrees) in the close-loop auditory stimulations of SW. Angles at 90 degree from this phase produce a slight decrease in SW amplitude. Interestingly, the order in which the phase changes were presented (clockwise vs anti-clockwise) seems to produce different amplitude effects (larger in anti-clockwise order by a factor of 2 for similar phase range). Slow wave enhancement via auditory stimulation is very sensitive to the phase of the SW oscillation. The order of presentation of the pulses is different in the (clock-wise vs anti-clockwise direction) seems to affect the amplitude. This phenomenon needs to be explored further as it could elucidate important aspects of SW physiology. The study was conducted with private fundings from Deep Knowledge Ventures.

Characteristics of ictal EEG in Magnetic Seizure Therapy at various stimulation frequencies

ObjectivesThe first objective of this study aimed to elucidate the relationship between seizure characteristics and Magnetic Seizure Therapy (MST) treatment outcome. The second objective was to determine the effect of stimulation frequency on seizure characteristics. MethodsUsing a between-subjects design, we compared the seizures of patients with unipolar depression receiving MST at three separate stimulation frequencies: 25 Hz (n = 34), 50 Hz (n = 16) and 100 Hz (n = 11). Seizures were rated for overall seizure adequacy on a scale of 0–6, with one point given for each measure that was considered to be adequate according to the ECT literature: (1) seizure EEG duration (2) motor duration, (3) post-ictal suppression, (4) ictal EEG maximum amplitude, (5) Global Seizure Strength, and (6) Symmetry. Mixed-effect models were used to evaluate the effect of frequency on seizure characteristics and the relationships between seizure characteristics and clinical outcome. Results(1) 100 Hz induced seizures that were less adequate than seizures induced with 50 Hz and 25 Hz stimulations. Seizures induced by 50 Hz stimulations had longer slow-wave phase durations and total EEG durations than the 100 Hz and 25 Hz groups. Global seizure strength was less robust in seizures induced by 100 Hz MST compared to the other stimulation frequencies. (2) Shorter polyspike durations and smaller slow-wave amplitude predicted reductions in overall symptoms of depression as measured by the 24-item Hamilton Depression Scale. ConclusionAnalysis of our first objective revealed stimulation frequency significantly influences measures of overall seizure adequacy. However, our results also revealed these descriptions of seizure adequacy based on ECT literature may not be useful for MST-induced seizures, as the characteristics of MST-induced seizure characteristics may predict clinical response in a different manner. SignificanceThese results may help to distinguish the biological processes impacted by stimulation frequency and may suggest different mechanisms of action between convulsive therapies and challenge the current understanding of seizure adequacy for MST.

High Amplitude Background Slow Waves in Normal Children Aged 3 to 18 Months: Implications for the Consideration of Hypsarhythmia.

To assess for the presence of high amplitude EEG background slow waves in normal young children. One hundred children with normal development ages 3 to 18 months had normal EEGs for spells and did not have seizures or epilepsy. Three electroencephalographers retrospectively reviewed 5 minutes of stable stage II sleep to measure background slow waves for peak-to-peak amplitudes. A standard 10-20 longitudinal bipolar montage was used. Interrater agreement was assessed by intraclass correlation coefficient. Interrater agreement between reviewers in the assessment of recurrent slow wave amplitudes was excellent (intraclass correlation coefficient = 0.97). Slow wave amplitudes were the highest in the posterior head regions for all patients. We found recurring slow waves of <200 µV, 200 to 299 µV, 300 to 399 µV, 400 to 499 µV, and >500 µV in 17%, 49%, 30%, 3% and 1%, respectively. Although hypsarhythmia typically includes high amplitude background slow waves of >200 or >300 µV, we found that 83% and 34% of normal children had recurring posterior background slow waves of >200 or >300 µV, respectively. These data may be useful in the EEG background assessment of young children, for determining the presence or absence of hypsarhythmia, and determining treatment response in children with epileptic spasms.