Delta Wave Amplitude Research Articles

Effects of CPAP treatment on electroencephalographic activity in patients with obstructive sleep apnea syndrome during deep sleep: Preliminary findings of a cross-sectional study.

Study objectives: To investigate whether electroencephalographic (EEG) activities during non-rapid eye movement sleep stage 3 (N3) in obstructive sleep apnea syndrome (OSAS) patients were changed with continuous positive airway pressure (CPAP) treatment.Methods: A cross-sectional study of EEG activity during N3 sleep was conducted in 15 patients with moderate to severe OSAS without and with CPAP treatment compared to 15 normal controls. The amplitude, and absolute and relative power of delta, theta, alpha and beta waves as well as the absolute power ratio of slow to fast EEG waves (i.e., absolute power of delta and theta waves/absolute power of alpha and beta waves) and the spectral power density of 0-30Hz EEG activities were analyzed.Results: CPAP significantly increased N3 sleep, the absolute and relative powers, amplitudes of delta and theta waves, and absolute power ratio of slow to fast EEG waves, but decreased relative alpha and beta powers during N3 sleep. However, there were no significant differences in those parameters between the OSAS patients with CPAP treatment and normal controls.Conclusions: CPAP prolongs N3 sleep and increases the power and amplitude of slow EEG waves during N3 sleep, which indicates an improvement in sleep quality and further provides evidence for recommendation of CPAP treatment for OSAS patients.

Hypertrophic Cardiomyopathy and Ventricular Preexcitation in the Young: Cause and Accessory Pathway Characteristics.

The cause of hypertrophic cardiomyopathy (HCM) in the young is highly varied. Ventricular preexcitation (preexcitation) is well recognized, yet little is known about the specificity for any cause and the characteristics of the responsible accessory pathways (AP). Retrospective cohort study of patients <21 years of age with HCM/preexcitation from 2000 to 2022. The cause of HCM was defined as isolated HCM, storage disorder, metabolic disease, or genetic syndrome. Atrioventricular AP (true AP) were distinguished from fasciculoventricular fibers (FVF) using standard invasive electrophysiology study criteria. AP were defined as high risk if any of the following were <250 ms: shortest preexcited RR interval in atrial fibrillation, shortest paced preexcited cycle length, or anterograde AP effective refractory period. We identified 345 patients with HCM and 28 (8%) had preexcitation (isolated HCM, 10/220; storage disorder, 8/17; metabolic disease, 5/19; and genetic syndrome, 5/89). Six (21%) patients had clinical atrial fibrillation (1 with shortest preexcited RR interval <250 ms). Twenty-two patients underwent electrophysiology study which identified 23 true AP and 16 FVF. Preexcitation was exclusively FVF mediated in 8 (36%) patients. Five (23%) patients had AP with high-risk conduction properties (including ≥1 patient in each etiologic group). Multiple AP were seen in 8 (36%) and AP plus FVF in 10 (45%) patients. Ablation was acutely successful in 13 of 14 patients with recurrence in 3. One procedure was complicated by complete heart block after ablation of a high-risk midseptal AP. There were significant differences in QRS amplitude and delta wave amplitude between groups. There were no surface ECG features that differentiated AP from FVF. Young patients with HCM and preexcitation have a high likelihood of underlying storage disease or metabolic disease. Nonisolated HCM should be suspected in young patients with large QRS and delta wave amplitudes. Surface ECG is not adequate to discriminate preexcitation from a benign FVF from that secondary to potentially life-threatening AP.

PO-03-125 VENTRICULAR PREEXCITATION AND PEDIATRIC HYPERTROPHIC CARDIOMYOPATHY: ETIOLOGY AND ACCESSORY PATHWAY CHARACTERISTICS

The etiology of pediatric hypertrophic cardiomyopathy (HCM) is varied. Ventricular preexcitation (VPe) is well recognized, yet little is known regarding the specific etiology, and accessory pathways (AP) characteristics. Define the etiology of HCM in patients with VPe and the characteristics of the responsible APs. Retrospective cohort study of patients <21 years of age with HCM/VPe from 2000-22. The etiology was defined as sarcomeric/non-sarcomeric (isolated HCM), storage disorder, metabolic disease, or genetic syndrome. AP were designated as atrioventricular (AV) or fasciculoventricular fibers (FVF) using standard invasive EP study criteria when available. AV APs were defined as high risk if any of the following were <250 ms: shortest preexcited RR interval in AF, shortest paced preexcited cycle length, or APERP. ECG characteristics were compared in patients with VPe exclusively secondary to an FVF to those with anteroseptal AP-mediated VPe. From a total of 345 patients with HCM, 28 (8%) had VPe and proportion with VPe varied significantly between etiologic groups: isolated HCM 10/220 (5%), storage 8/17 (47%), metabolic 5/19 (26%), genetic syndrome 5/89 (6%), p < 0.001. Six (21%) had clinical AF (1 with SPPRI <250 ms, 4 with storage disease). Invasive EP study was performed in 22, identifying 39 APs (23 AV AP, 16 FVF; fig 1). VPe resulted exclusively from an FVF in 8 (36%) patients. Multiple AV APs were seen in 8 (36%) and AV AP plus FVF in 10 (45%). Five (23%) patients had AV APs with high-risk conduction properties (≥1 in each etiologic group). Ablation was acutely successful in 13/14 patients with recurrence in 3. The only complication was a single case of heart block after ablation of a high-risk midseptal AP. Patients with storage disease had larger QRS amplitudes (median 42.3 v. 23.0 mm, p < 0.01). The delta wave amplitude did not discriminate between anteroseptal AP and FVF (median 4.3 v. 4.1 mm, p = 0.92). VPe and high risk or multiple AP may be associated with any etiology of childhood HCM. This is most common in storage disorders associated with high QRS amplitudes and clinical AF, with important implications for prognosis and management.

Somatostatin neuron contributions to cortical slow wave dysfunction in adult mice exposed to developmental ethanol.

Transitions between sleep and waking and sleep-dependent cortical oscillations are heavily dependent on GABAergic neurons. Importantly, GABAergic neurons are especially sensitive to developmental ethanol exposure, suggesting a potential unique vulnerability of sleep circuits to early ethanol. In fact, developmental ethanol exposure can produce long-lasting impairments in sleep, including increased sleep fragmentation and decreased delta wave amplitude. Here, we assessed the efficacy of optogenetic manipulations of somatostatin (SST) GABAergic neurons in the neocortex of adult mice exposed to saline or ethanol on P7, to modulate cortical slow-wave physiology. SST-cre × Ai32 mice, which selectively express channel rhodopsin in SST neurons, were exposed to ethanol or saline on P7. This line expressed similar developmental ethanol induced loss of SST cortical neurons and sleep impairments as C57BL/6By mice. As adults, optical fibers were implanted targeting the prefrontal cortex (PFC) and telemetry electrodes were implanted in the neocortex to monitor slow-wave activity and sleep-wake states. Optical stimulation of PFC SST neurons evoked slow-wave potentials and long-latency single-unit excitation in saline treated mice but not in ethanol mice. Closed-loop optogenetic stimulation of PFC SST neuron activation on spontaneous slow-waves enhanced cortical delta oscillations, and this manipulation was more effective in saline mice than P7 ethanol mice. Together, these results suggest that SST cortical neurons may contribute to slow-wave impairment after developmental ethanol.

Drivers’ Workload Electroencephalogram Characteristics in Cognitive Tasks Based on Improved Multiscale Sample Entropy

Cognitive workload is an internal factor that can be influenced by external factors. When drivers are distracted by these internal and external influences, their ability to drive safely can be compromised. Electroencephalogram (EEG) is a non-invasive neuroimaging technique that measures the electrical activity of the brain. and it can provide information about brain activity related to various cognitive and motor functions. In this study, on-road driving experiments were conducted to investigate the EEG characteristics of drivers under different levels of cognitive workload generated through mathematical calculations with varying difficulties. The collected EEG signals were processed using continuous wavelet transform to decompose them into delta, theta, alpha, beta, and gamma waveforms. Numerical values and power spectral characteristics of each waveband in the left and right frontal regions of the driver were then analyzed. Furthermore, the study utilized an improved multiscale sample entropy algorithm to analyze the EEG entropy characteristics of drivers in different states. The results indicate that under different degrees of cognitive workload, the amplitude of delta, theta, and alpha waves decreased, while beta and gamma waves showed significant changes. The improved multiscale sample entropy algorithm provided a more objective assessment of changes in entropy across different wavebands and stages, with smaller entropy fluctuation ranges and more accurate complexity changes. Overall, this research provides valuable insights into the characteristics of drivers under cognitive workload, contributing to the analysis of human factors in driving safety. These findings can inform the development of strategies to mitigate the adverse effects of cognitive workload on driving performance and enhance overall road safety.

Instability of non-REM sleep in older women evaluated by sleep-stage transition and envelope analyses.

Traditionally, age-related deterioration of sleep architecture in older individuals has been evaluated by visual scoring of polysomnographic (PSG) recordings with regard to total sleep time and latencies. In the present study, we additionally compared the non-REM sleep (NREM) stage and delta, theta, alpha, and sigma wave stability between young and older subjects to extract features that may explain age-related changes in sleep. Polysomnographic recordings were performed in 11 healthy older (72.6 ± 2.4 years) and 9 healthy young (23.3 ± 1.1 years) females. In addition to total sleep time, the sleep stage, delta power amplitude, and delta, theta, alpha, and sigma wave stability were evaluated by sleep stage transition analysis and a novel computational method based on a coefficient of variation of the envelope (CVE) analysis, respectively. In older subjects, total sleep time and slow-wave sleep (SWS) time were shorter whereas wake after sleep onset was longer. The number of SWS episodes was similar between age groups, however, sleep stage transition analysis revealed that SWS was less stable in older individuals. NREM sleep stages in descending order of delta power were: SWS, N2, and N1, and delta power during NREM sleep in older subjects was lower than in young subjects. The CVE of the delta-band is an index of delta wave stability and showed significant differences between age groups. When separately analyzed for each NREM stage, different CVE clusters in NREM were clearly observed between young and older subjects. A lower delta CVE and amplitude were also observed in older subjects compared with young subjects in N2 and SWS. Additionally, lower CVE values in the theta, alpha and sigma bands were also characteristic of older participants. The present study shows a decrease of SWS stability in older subjects together with a decrease in delta wave amplitude. Interestingly, the decrease in SWS stability coincided with an increase in short-term delta, theta, sigma, and alpha power stability revealed by lower CVE. Loss of electroencephalograms (EEG) variability might be a useful marker of brain age.

Electrocardiographic and electrophysiological characteristics of fasciculoventricular fibers in children.

Fasciculoventricular fiber (FVF) that does not cause tachyarrhythmia is a rare form of ventricular preexcitation, which is important to distinguish from Kent fibers. Although, adenosine and some electrocardiographic features are important in the differentiation of Wolff Parkinson White (WPW) than FVF, a clear distinction may not always be possible without an electrophysiological study (EPS). In this study, we aimed to present the clinical and electrophysiological features of our pediatric patients with fasciculoventricular fiber. Between October 2013 and September 2021, 565 patients who underwent electrophysiological studies due to ventricular preexcitation in our clinic were screened in the study, and 27 (4.7%) patients with fasciculoventricular fiber were included. The data of the patients were obtained from the file records using the electronic internet database system Filemaker® . Electrophysiological study age, weight, gender, symptom, and presence of congenital heart disease of the patients were obtained from the file records. Accessory pathway localization was evaluated according to the modified Arruda algorithm in pre-procedural electrocardiography. In addition, delta wave amplitudes were measured in the first 40ms from the surface ECG. PR interval, QRS interval, and delta wave amplitude were recorded before and after ablation in patients with additional accessory pathways. Post-procedure values were included in the FVF group. The mean age of the patients was 11.47±4.25 years. All 70.4% of the reasons for admission were symptoms such as palpitations and syncope. Two patients had hypertrophic cardiomyopathy and 1 patient had ccTGA. In the electrophysiological study, additional manifest WPW was found in 9 (33%) patients (3 patients with high risk, 6 patients with orthodromic supraventricular tachycardia), focal atrial tachycardia in a patient, and atrioventricular nodal reentry tachycardia in a patient. While the delta wave amplitude was found to be 2.56±1.38(1-5.5) mm in the first 40ms in surface electrocardiography in 9 patients with additional accessory pathway, it was found to be 1.64±0.67(0.5-3) mm in the FVF group. There was no statistically significant difference between the 2 groups (p=.398). Delta wave amplitude>3.5mm was not detected in any patient with isolated FVF. Interestingly, delta wave amplitude was<3.5mm in 7 (78%) of 9 patients who were identified and ablated with an additional accessory pathway. Total 19 of the patients (59.3%) were adenosine-responsive (18 isolated FVF, 1 manifest AP+FVF adenosine-responsive. 8 patients with other manifest AP + FVF had no pre-procedural adenosine-asystole response, and all of them QRS were expanded). Although, the fasciculoventricular fibers themselves are not the cause of tachyarrhythmia, the accessory pathway and other tachyarrhythmia substrate frequency accompanying these cases are quite high (approximately 40%) in EPS. The delta wave characteristics of ablated patients are very similar to FVF patients. While all patients with isolated FVF were adenosine responsive, most of those with additional manifest WPW were unresponsive. Therefore, performing EPS in patients with suspected FVF based on surface ECG features seems to be important for the detection of additional tachyarrhythmias and risky accessory pathways.

Effectiveness of the VR Cognitive Training for Symptom Relief in Patients with ADHD

This study aimed to verify the effectiveness of virtual reality (VR) cognitive training by measuring the sense of presence and electroencephalography (EEG) in children with ADHD. A clinical trial was conducted to verify the effect of VR cognitive training on children with ADHD. The experimental group included eight children with ADHD, and the control group included eight healthy children without ADHD. The sense of presence increased significantly after the VR cognitive training in children with ADHD. Also, no significant changes in the alpha, beta, delta, and gamma wave amplitudes were found in both groups after the VR cognitive training. Thus, the VR training content developed in this study can help measure the patients’ behavioral inhibition, increase their sense of presence by inducing interaction with distraction stimuli, and alleviate their symptoms. However, EEG could only be used as an auxiliary means, at the clinician’s judgment, for ADHD diagnosis in children because no significant EEG changes were observed in the experimental or control groups after the VR cognitive training.

The relationship between snoring sounds and EEG signals on polysomnography.

The aim of this study was to analyze the relationship of snoring sound signals obtained by polysomnography (PSG) in the sleep laboratory with cortical EEG (6 channel) signals to find answers to two important questions that have been covered to a limited extent in the literature: (1) Would the sounds generated by a snoring individual have an effect on the cerebral electrical waves occurring during sleep (specifically deep restorative sleep)? (2) Would the snoring sounds of an individual being examined by PSG have more of an effect on any one of the EEG electrodes? PSG recordings were obtained from volunteers with primary snoring and those withobstructive sleep apnea syndrome (OSAS) on six different EEG channels (F4-M1, C4-M1, and O2-M1, F3-M2, C3-M2, and O1-M2). The relationship of each of these recordings and snoring sound signals was analyzed by using a computer-based electrophysiological signal analysis method. A three-tier approach was used in this relationship: "Feature extraction, Feature selection, andClassification". Data were obtained from a total of 40 volunteers (32 men, mean age (± SD) 47.5± 3.2 years), 20 with primary snoring and 20 with OSAS. The discrete wavelet transform (DWT) feature extraction method was the most successful method, and by utilizing this method for analyzing EEG channels, snoring sound signals were found to affect theC3-M2 channel the most (Duncan test, p < 0.05). Delta wave frequency levels during snoring were decreased compared to both before snoring (p = 0.160) and after snoring (p = 0.04) periods (paired sample test). When snoring sounds and EEG signals were analyzed for frequency, time, and wave conversion with feature extraction methods, theC3-M2 channel was to be found the most affected channel.The sleep physiologist who made the PSG analyses reported that, among the 6 EEG channels analyzed for periods where there was no apnea or hypopnea events but only snoring, C3-M2 was the channel showing changes in delta wave activity. Our study showed that the monotonous and repetitive snoring sounds of the snorer do not wake the individual, but doaffect deep restorative sleep (N3). PSG signal analysis revealed that the most significant changes were in the C3-M2 channel (N3 delta wave amplitude increase and frequency decrease during snoring). Thus, clinicians may be able to monitor the characteristic changes occuring in large cortical delta waves in snoring individuals with innovative single-channel EEG devices without microphones.

Effects of Cortical Cooling on Activity Across Layers of the Rat Barrel Cortex.

Moderate cortical cooling is known to suppress slow oscillations and to evoke persistent cortical activity. However, the cooling-induced changes in electrical activity across cortical layers remain largely unknown. Here, we performed multi-channel local field potential (LFP) and multi-unit activity (MUA) recordings with linear silicone probes through the layers of single cortical barrel columns in urethane-anesthetized rats under normothermia (38°C) and during local cortical surface cooling (30°C). During cortically generated slow oscillations, moderate cortical cooling decreased delta wave amplitude, delta-wave occurrence, the duration of silent states, and delta wave-locked MUA synchronization. Moderate cortical cooling increased total time spent in the active state and decreased total time spent in the silent state. Cooling-evoked changes in the MUA firing rate in cortical layer 5 (L5) varied from increase to decrease across animals, and the polarity of changes in L5 MUA correlated with changes in total time spent in the active state. The decrease in temperature reduced MUA firing rates in all other cortical layers. Sensory-evoked MUA responses also decreased during cooling through all cortical layers. The cooling-dependent slowdown was detected at the fast time-scale with a decreased frequency of sensory-evoked high-frequency oscillations (HFO). Thus, moderate cortical cooling suppresses slow oscillations and desynchronizes neuronal activity through all cortical layers, and is associated with reduced firing across all cortical layers except L5, where cooling induces variable and non-consistent changes in neuronal firing, which are common features of the transition from slow-wave synchronization to desynchronized activity in the barrel cortex.

Slowing of Alpha Waves on EEG, an Early Marker of Minimal Hepatic Encephalopathy

Introduction: Minimal Hepatic Encephalopathy (MHE) is the mildest form of spectrum of Hepatic Encephalopathy (HE) which remains undiagnosed due to lack of awareness. MHE has a negative effect on patient's daily functioning due to cognitive impairment. Electro-Encephalo-Gram (EEG) and Mini Mental State Examination (MMSE) are useful in early diagnosis and follow up of MHE. Aim: To study evidence of MHE in patients with liver cirrhosis by psychometric tests and also its correlation with EEG changes. Materials and Methods: The study was carried out as a prospective case control study of 70 patients diagnosed with Cirrhosis of liver, over a period of two years in accordance with European Association for the Study of the Liver (EASL) and Asociacion Latinoamericana parael Estudio del Higado (ALEH) criteria with MMSE score &gt;24 and were diagnosed as Minimal Hepatic Encephalopathy if 2 out of 3 psychometric tests were abnormal EEG was performed in them and was compared with 70 healthy controls. Results: Study showed male predominance (90%) with mean age of 45.49 ± 11.76. Alcohol related cirrhosis (70%) was found to be more common than HBV (8.57%) and HCV (2.86%) infection related cirrhosis. Pedal edema, icterus, pallor and ascites were the most common presenting manifestations. Most cirrhotic cases (80%) were under Child Pugh Class-A. On USG of abdomen all cases had Coarse echotexture and nodular surface of liver among them 11 cases had Hepatomegaly, 10 cases had splenomegaly, 42 cases had ascites and 24 cases had increased portal venous diameter of mean size 14.02 ± 0.48 mm. MMSE score of all selected cirrhotic cases was &gt;24. Psychometric Tests i.e. Number Connection Test-A, Number Connection Test-B and Line tracing test were performed in all selected cirrhotic cases and they were not able to perform it within designated time. All cases were subjected to EEG and compared with equal number of comparable healthy controls, which shows change in frequency and amplitude of Alpha wave which was highly significant whereas no significant changes of frequency and amplitude of Beta, Theta and Delta waves between cases and controls. Conclusion: There is significant changes in alpha wave frequency and amplitude in patients with minimal hepatic encephalopathy.

Differentiation of fasciculoventricular fibers from anteroseptal accessory pathways using the surface electrocardiogram

Fasciculoventricular fibers (FVFs) are responsible for 1%-5% of cases of asymptomatic preexcitation on the surface electrocardiogram (ECG). Unlike ventricular preexcitation seen in Wolff-Parkinson-White (WPW) syndrome, FVFs are not associated with sudden cardiac death from preexcited atrial fibrillation. The purpose of this study was to identify surface ECG variables that differentiate FVFs from true WPW syndrome. This is a retrospective case-control study comparing surface ECG characteristics of patients diagnosed with FVFs (cases) with those of patients with WPW syndrome and anteroseptal accessory pathways (controls) via intracardiac electrophysiology testing at a single institution from 2005 to2017. Twenty-four cases of FVFs confirmed by intracardiac electrophysiology testing were identified and compared with 48 consecutive controls with WPW syndrome and anteroseptal accessory pathways. Patients with WPW syndrome were found to have significantly higher delta wave amplitudes (4.8 ± 2.0 mm vs 1.9 ± 1.3 mm; P < .001), shorter PR intervals (94.6 ± 12.5 ms vs 106.8 ± 13.2 ms; P < .001), and longer QRS intervals (133.6 ± 19.0 ms vs 118.7 ± 24.7 ms; P = .006) than did those with FVFs. Multivariable logistic regression analysis identified the delta wave amplitude as the only independent predictor of WPW syndrome (odds ratio 3.1 per 1-mm increase; bootstrapped 95% confidence interval 1.5-6.4; c statistic 0.90; P = .002). The etiology of preexcitation in patients with an anteroseptal preexcitation pattern, whether because of a benign FVF or because of potentially serious WPW syndrome, can be noninvasively deduced using the surface ECG. A higher delta wave amplitude is an independent risk factor for the presence of WPW syndrome and can accurately distinguish WPW syndrome from a FVF with good test accuracy characteristics.

Sensory and movement evoked EEG patterns in the preterm neonate

Due to the similarities between EEG activity of humans during second trimester of gestation and the activity patterns of neonatal rodents, the latter became valuable model to study the mechanisms by which early patterns of activity may act as template for later-emerging functional maps [2] . In rodents, early EEG activity (Spindles Bursts [SB]) are generated within a complex neural network including the peripheral sensory organs, subcortical nuclei as well as cortical areas. In the barrel cortex, sensory evoked SB contain early gamma oscillations (EGO) that are primarily driven by rhythmic gamma excitation from the thalamus and enable precise temporal binding of the topographically aligned thalamic and cortical neurons. EGO support long-term dependent potentiation in the thalamo-cortical synapses [1] . Characteristic preterm EEG patterns of “Delta-brushes” (DBs) are spontaneous EEG activities and have been reported in the sensory cortices following sensory stimuli and spontaneous movements. Spatiotemporal analyses of the cortical auditory-evoked responses (AERs) using 32-electrode EEG recordings in healthy neonates aged 30 to 38 post-menstrual weeks (PMW) showed that AERs are characterized by a power spectrum increase at frequency bands ranging from delta to gamma on the electrodes overlaying temporal regions. Time-frequency wavelet analysis also showed that fast (alpha-gamma) oscillations co-occurred with the auditory-evoked delta wave from around 650 ms after the stimulus and lasted for nearly 700 ms. Stimulus locked averaging disclosed cortical auditory-evoked potentials (CAEP) with negative high amplitude delta waves peaking successively over middle and posterior temporal regions. Thus, auditory-evoked DBs in preterm neonates are slow delta waves nesting fast oscillations in the temporal regions and correspond to the late part of CAEPs, which is lost when using classical CAEP processing [3] . Decreasing from 30 to 38 PMW, this EEG pattern is thus associated with the prenatal development of sensory processing circuits and likely participate to the cortical maps maturation.

Local Use-Dependent Sleep in Wakefulness Links Performance Errors to Learning.

Sleep and wakefulness are no longer to be considered as discrete states. During wakefulness brain regions can enter a sleep-like state (off-periods) in response to a prolonged period of activity (local use-dependent sleep). Similarly, during nonREM sleep the slow-wave activity, the hallmark of sleep plasticity, increases locally in brain regions previously involved in a learning task. Recent studies have demonstrated that behavioral performance may be impaired by off-periods in wake in task-related regions. However, the relation between off-periods in wake, related performance errors and learning is still untested in humans. Here, by employing high density electroencephalographic (hd-EEG) recordings, we investigated local use-dependent sleep in wake, asking participants to repeat continuously two intensive spatial navigation tasks. Critically, one task relied on previous map learning (Wayfinding) while the other did not (Control). Behaviorally awake participants, who were not sleep deprived, showed progressive increments of delta activity only during the learning-based spatial navigation task. As shown by source localization, delta activity was mainly localized in the left parietal and bilateral frontal cortices, all regions known to be engaged in spatial navigation tasks. Moreover, during the Wayfinding task, these increments of delta power were specifically associated with errors, whose probability of occurrence was significantly higher compared to the Control task. Unlike the Wayfinding task, during the Control task neither delta activity nor the number of errors increased progressively. Furthermore, during the Wayfinding task, both the number and the amplitude of individual delta waves, as indexes of neuronal silence in wake (off-periods), were significantly higher during errors than hits. Finally, a path analysis linked the use of the spatial navigation circuits undergone to learning plasticity to off periods in wake. In conclusion, local sleep regulation in wakefulness, associated with performance failures, could be functionally linked to learning-related cortical plasticity.

Effect of mother's voice on neonatal respiratory activity and EEG delta amplitude.

While the influence of the mother's voice on neonatal heart‐rate response and its relevant activity on cerebral cortex and the autonomic nervous system (ANS) are well known, few studies have assessed its influence on respiratory activity. We investigated the relationship among the respiration rate, the delta wave amplitudes through electroencephalography, and the basal state of ANS through the respiratory variability index while 22 full‐term neonates hear their mother's voice and an unknown voice. It was found that when respiratory variability was large, a transient (<5 s) change in respiration rates was observed in response to an unknown voice, while a greater increase in the delta wave amplitude was observed in the frontal lobe than the parietal one in response to the mother's voice. Conversely, when respiratory variability was small, a sustained increase (>10 s) in respiration rates was observed in response to the mother's voice, while a greater increase in the delta wave amplitude was found in both the frontal and parietal lobes. These results suggest that the basal state of ANS influences the latency of increases in respiration rates. Furthermore, induced by the mother's voice, transient increases in respiration rates are reduced in association with frontal lobe activity, and sustained increases in respiration rates are promoted in association with frontal and parietal lobe activities.

Intracarotid Etomidate Decreases the Interhemispheric Synchronization in Electroencephalogram (EEG) During the Wada Test.

The Wada test is a diagnostic method to anesthetize 1 cerebral hemisphere and assess the language and memory functions of awake contralateral hemisphere before temporal lobectomy in patients with epilepsy. The effects of an ipsilateral injection of etomidate on the functional properties of contralateral hemisphere are not known. Our aim was to characterize the electroencephalographic (EEG) effects after intracarotid injection of etomidate and to determine the changes in synchronization between the ipsilateral and contralateral hemispheres. We retrospectively analyzed EEG data from 15 patients who underwent Wada test with etomidate. Continuous EEG data from 4 electrodes (2 anterior [F3, F4] and 2 posterior [P3, P4]) were analyzed. After artifact rejection, we measured the amplitudes of delta (1 to 4 Hz) and alpha (7 to 13 Hz) waves and the changes in the interhemispheric synchronization before, during, and after etomidate injection. Ipsilateral injection of etomidate causes EEG changes in both hemispheres with increased amplitude of delta waves anteriorly and the alpha waves posteriorly. However this effect of etomidate is not uniform. Although there was a decrease in the interhemispheric synchronization of delta waves, there was no change in the synchronization of the alpha waves. Our study showed that the EEG effects of intracarotid ipsilateral injection of etomidate is not uniform in both hemispheres. Decrease in the interhemispheric synchronization of delta waves might serve as an indicator of ipsilateral effect of etomidate on the brain. Additional studies are needed to confirm our findings.

S21-4. Neuropathological hypothesis of sleep dysfunction in Schizophrenia

The purpose of this lecture is to review the polysomnographic non-rapid eye movement sleep abnormalities in schizophrenic patients and to present evidence for possible pathophysiologic mechanisms. Deficits of delta wave sleep are commonly reported sleep architecture abnormalities in schizophrenia. In the1960’s, Feinberg described this abnormality and about twenty years later, he first proposed that a decline in synaptic density resulting from abnormal reorganization of brain structure during early adolescence might cause the decline in delta wave amplitude and the onset of schizophrenia. Recent neuropathological studies of schizophrenia revealed that the dendritic spine density was particularly reduced in layer three of the neocortex. And excessive spine pruning is now considered a potential factor underlying reduced cortical gray matter volume in schizophrenia. Aberrant neuronal pruning is also believed to contribute to compromise the thalamocortical circuitry. Several recent studies have reported markedly reduced sleep spindle activity mediated by thalamocortical circuits in schizophrenia. Animal studies have reported sleep spindles have been linked to synaptic plasticity and memory consolidation. Thus, aberrant pruning can result in structural brain abnormalities and deficits of two distinct rhythms during sleep. Furthermore, each of these impairments appears to be associated with both cognitive deficits and symptoms of schizophrenia.

Cortical activity in tinnitus patients and its modification by phonostimulation

OBJECTIVE:The goal of this study was to observe spontaneous cortical activity and cortical activity modulated by tinnitus-matched sound in tinnitus patients and healthy subjects with no otoneurologic symptoms.METHOD:Data were prospectively collected from 50 tinnitus patients and 25 healthy subjects. Cortical activity was recorded in all subjects with eyes closed and open and during photostimulation, hyperventilation and acoustic stimulation using 19-channel quantitative electroencephalography. The sound applied in the tinnitus patients was individually matched with the ability to mask or equal the tinnitus. The maximal and mean amplitude of the delta, theta, alpha and beta waves and the type and amount of the pathologic EEG patterns were noted during each recording. Differences in cortical localization and the influence of sound stimuli on spontaneous cortical activity were evaluated between the groups.RESULTS:The tinnitus group exhibited decreased delta activity and increased alpha and beta activity. Hyperventilation increased the intensity of the differences. The tinnitus patients had more sharp-slow waves and increased slow wave amplitude. Sound stimuli modified the EEG recordings; the delta and beta wave amplitudes were increased, whereas the alpha-1 wave amplitude was decreased. Acoustic stimulation only slightly affected the temporal region.CONCLUSION:Cortical activity in the tinnitus patients clearly differed from that in healthy subjects, i.e., tinnitus is not a “phantom” sign. The changes in cortical activity included decreased delta wave amplitudes, increased alpha-1, beta-1 and beta-h wave amplitudes and pathologic patterns. Cortical activity modifications occurred predominantly in the temporal region. Acoustic stimulation affected spontaneous cortical activity only in tinnitus patients, and although the applied sound was individually matched, the pathologic changes were only slightly improved.

Photoperiod Alters Duration and Intensity of Non–Rapid Eye Movement Sleep Following Immune Challenge in Siberian Hamsters (Phodopus sungorus)

Sleep is regulated by circadian and homeostatic processes, but can be altered by infectious disease. During infection or exposure to inflammatory stimuli, such as bacterial lipopolysaccharide (LPS), the duration and intensity of non–rapid eye movement sleep (NREMS), as measured by electoencephalogram (EEG) delta waves (.5–4 Hz), increase. These sleep alterations are hypothesized to conserve or redirect energy for immune system activation. Many vertebrates exhibit seasonal changes in immune function and sleep-wake cycle, and photoperiod (day length) serves as a reliable environmental cue. For example, winter is energetically demanding for most animals, and Siberian hamsters (Phodopus sungorus) adapted to short winter day lengths display reduced fever after LPS administration to presumably conserve energy. We hypothesized that short days increase the duration and intensity of NREMS after LPS challenge to create additional energy savings, despite evidence to the contrary that high fever is associated with increased NREMS. Male hamsters were housed under long (16 h light (L):8 h dark (D)) or short (8L:16D) day lengths, and chronically implanted with transmitters that recorded EEG and electromyogram (EMG) biopotentials simultaneously or core body temperature. After >10 wks in photoperiod conditions, hamsters received an i.p. injection of LPS or saline (control), and vigilance states (duration and distribution of NREMS, rapid eye movement sleep (REMS), and wakefulness) and EEG delta power spectra (NREMS intensity) were assessed. As expected, LPS treatment increased the duration and intensity of NREMS compared to controls. Hamsters adapted to short photoperiods exhibited cumulatively larger increases in NREMS duration and EEG delta wave amplitude 0–8 h after LPS injection compared to long-day LPS-treated hamsters despite short-day attenuation of fever. These results suggest a seasonal decoupling of LPS-induced fever with sleep to promote energy conservation during predictable energy shortages. Ultimately, the combination of increased sleep and reduced fever could represent a suite of physiological adaptations that increase the probability of surviving winter. (Author correspondence: Noah.Ashley@osumc.edu)

Spurious index drop due to large amplitude delta waves in sevoflurane induction with VCRII protocol

Spurious index drop due to large amplitude delta waves in sevoflurane induction with VCRII protocol