Increase In Alpha Power Research Articles

0036 ARC Genotype Modulates REM EEG Spectral Power Following Total Sleep Deprivation

Abstract Introduction EEG spectral power in the alpha range is indicative of a wake-like state, with alpha power typically high during wakefulness and reduced during sleep. We previously reported that a single nucleotide polymorphism (SNP) of the activity-regulated cytoskeleton associated protein (ARC) gene modulates non-REM theta and alpha spectral power. Here we sought to determine whether ARC genotype is also associated with phenotypic differences in EEG spectral power during REM sleep. Methods 43 healthy adults (27.6±4.8y; 23 females) participated in one of two in-laboratory studies. Each participant had a 10h baseline sleep opportunity (22:00–08:00), 38h TSD, and 10h recovery sleep opportunity (22:00–08:00). Sleep periods were recorded polysomnographically and visually scored according to AASM criteria. Genomic DNA was assayed for the ARC c.*742 + 58C>T non-coding SNP, rs35900184. Log-transformed EEG spectral power (C3-M3 derivation) for REM sleep over 0.2 Hz frequency bins in each of four frequency bands – delta (0.8–4.0 Hz), theta (4.2–8.0 Hz), alpha (8.2–12.0 Hz), and beta (12.2–16.0 Hz) – was analyzed by band using mixed-effects ANOVA with fixed effects for ARC genotype, night (baseline, recovery), frequency bin, and their interactions. Analyses included study and age as covariates and a random effect over subjects on the intercept. Results The genotype distribution in this sample was 28 C/C homozygotes, 10 C/T heterozygotes, and 5 T/T homozygotes. There was a significant genotype by night interaction in the alpha band (F2,1560=23.80, p< 0.001). Compared to baseline sleep, T/T homozygotes had 13.0% more alpha power during post-TSD recovery sleep, whereas C/C homozygotes had 1.2% less alpha power and C/T heterozygotes had 3.2% less alpha power. This differential TSD effect for the ARC genotypes was not seen in the other spectral bands. Conclusion Our results show that ARC genotype mediates the REM sleep EEG response to TSD, with T/T homozygotes displaying a pronounced increase in REM alpha power following sleep deprivation. The ARC SNP has been associated with schizophrenia, a psychiatric disorder with known sleep disturbances. As such, the ARC-mediated increase in REM EEG alpha power for T/T homozygotes might be a marker of a psychosis-like predisposition. Support (if any) ONR N00014-13-1-0302; NIH R21CA167691; USAMRDC W81XWH-18-1-0100; ARO W911NF2210223

Quantitative Electroencephalographic Changes Associated With Brain Tissue Hypoxia After Pediatric Traumatic Brain Injury: A Retrospective Exploratory Analysis.

Brain tissue hypoxia is associated with poor outcomes after pediatric traumatic brain injury. Although invasive brain oxygenation (PbtO 2 ) monitoring is available, noninvasive methods assessing correlates to brain tissue hypoxia are needed. We investigated EEG characteristics associated with brain tissue hypoxia. We performed a retrospective analysis of 19 pediatric traumatic brain injury patients undergoing multimodality neuromonitoring that included PbtO 2 and quantitative electroencephalography(QEEG). Quantitative electroencephalography characteristics were analyzed over electrodes adjacent to PbtO 2 monitoring and over the entire scalp, and included power in alpha and beta frequencies and the alpha-delta power ratio. To investigate relationships of PbtO 2 to quantitative electroencephalography features using time series data, we fit linear mixed effects models with a random intercept for each subject and one fixed effect, and an auto-regressive order of 1 to model between-subject variation and correlation for within-subject observations. Least squares (LS) means were used to investigate for fixed effects of quantitative electroencephalography features to changes in PbtO 2 across thresholds of 10, 15, 20, and 25 mm Hg. Within the region of PbtO 2 monitoring, changes in PbtO 2 < 10 mm Hg were associated with reductions of alpha-delta power ratio (LS mean difference -0.01, 95% confidence interval (CI) [-0.02, -0.00], p = 0.0362). Changes in PbtO 2 < 25 mm Hg were associated with increases in alpha power (LS mean difference 0.04, 95% CI [0.01, 0.07], p = 0.0222). Alpha-delta power ratio changes are observed across a PbtO 2 threshold of 10 mm Hg within regions of PbtO 2 monitoring, which may reflect an EEG signature of brain tissue hypoxia after pediatric traumatic brain injury.

Microsaccades transiently lateralise EEG alpha activity.

The lateralisation of 8-12Hz alpha activity is a canonical signature of human spatial cognition that is typically studied under strict fixation requirements. Yet, even during attempted fixation, the brain produces small involuntary eye movements known as microsaccades. Here we report how spontaneous microsaccades - made in the absence of incentives to look elsewhere - can themselves drive transient lateralisation of EEG alpha power according to microsaccade direction. This transient lateralisation of posterior alpha power occurs similarly following start and return microsaccades and is, at least for start microsaccades, driven by increased alpha power ipsilateral to microsaccade direction. This reveals new links between spontaneous microsaccades and human electrophysiological brain activity. It highlights how microsaccades are an important factor to consider in studies relating alpha activity - including spontaneous fluctuations in alpha activity - to spatial cognition, such as studies on visual attention, anticipation, and working memory.

Frequency-following response effect according to gender using a 10-Hz binaural beat stimulation.

Several studies have continuously investigated FFRs using binaural beat (BB) stimulations and their related effects. However, only a few studies have investigated the differences in BB stimulation effects according to basic demographic characteristics, such as gender and age. This study aimed to determine the alpha wave activity after a 10-Hz BB stimulation and subsequently identify differences according to gender across all brain areas (frontal, central, parietal, temporal, and occipital areas). A total of 23 healthy adults (11 male and 12 female), aged 20-29, participated in the study. For the 10-Hz BB stimulation, pure tone auditory stimuli of 250 and 260 Hz were given to the left and right ear, respectively. Through a power spectrum analysis of the phase-excluding BBs (non-BBs) and phase-including 10-Hz BBs (α-BBs), the alpha power at each brain area was estimated. These values were compared using a mixed-design ANOVA. With the exception of the temporal area, all other brain areas showed a significant increase in alpha power for α-BBs compared to those of non-BBs. However, the difference according to gender was not significant. The results indicated the lack of gender effects in alpha wave generation through a 10-Hz BB stimulation.

Spatial attention is not affected by alpha or beta transcranial alternating current stimulation: A registered report

Using Electroencephalography (EEG) an event-related change in alpha activity has been observed over primary sensory cortices during the allocation of spatial attention. This is most prominent during top-down, or endogenous, attention, and nearly absent in bottom-up, or exogenous orienting. These changes are highly lateralised, such that an increase in alpha power is seen ipsilateral to the attended region of space and a decrease is seen contralaterally. Whether these changes in alpha oscillatory activity are causally related to attentional resources, or to perceptual processes, or are simply epiphenomenal, is unknown. If alpha oscillations are indicative of a causal mechanism whereby attention is allocated to a region of space, it remains an open question as to whether this is driven by ipsilateral increases or contralateral decreases in alpha power. This preregistered report set out to test these questions. To do so, we used transcranial Alternating Current Stimulation (tACS) to modulate alpha activity in the somatosensory cortex whilst measuring performance on established tactile attention paradigms. All participants completed an endogenous and exogenous tactile attention task in three stimulation conditions; alpha, sham and beta. Sham and beta stimulation operated as controls so that any observed effects could be attributed to alpha stimulation specifically. We replicated previous behavioural findings in all stimulation conditions showing a facilitation of cued trials in the endogenous task, and inhibition of return in the exogenous task. However, these were not affected by stimulation manipulations. Using Bayes-factor analysis we show strong support for the null hypotheses – that the manipulation of Alpha by tACS does not cause changes in tactile spatial attention. This well-powered study, conducted over three separate days, is an important contribution to the current debate regarding the efficiency of brain stimulation.

Assessing the development of mental fatigue during simulated flights with concurrent EEG-fNIRS measurement

Mental fatigue (MF) can impair pilots’ performance and reactions to unforeseen events and is therefore an important concept within aviation. The physiological measurement of MF, especially with EEG and, in recent years, fNIRS, has gained much attention. However, a systematic investigation and comparison of the measurements is seldomly done. We induced MF via time on task during a 90-min simulated flight task and collected concurrent EEG-fNIRS, performance and self-report data from 31 participants. While their subjective MF increased linearly, the participants were able to keep their performance stable over the course of the experiment. EEG data showed an early increase and levelling in parietal alpha power and a slower, but steady increase in frontal theta power. No consistent trend could be observed in the fNIRS data. Thus, more research on fNIRS is needed to understand its possibilities and limits for MF assessment, and a combination with EEG is advisable to compare and validate results. Until then, EEG remains the better choice for continuous MF assessment in cockpit applications because of its high sensitivity to a transition from alert to fatigued, even before performance is impaired.

Effect of homeostatic pressure on daytime vigilance performance: Evidence from behaviour and resting-state EEG.

Vigilance is highly sensitive to the time-of-day effect and goes through the daytime trough during the period of the post-noon dip. A midday nap could maintain individuals' vigilance at an optimal level. Thus, homeostatic sleep pressure is one of the main reasons for the post-noon dip in daytime vigilance. The current study focussed on the role of homeostatic sleep pressure in the diurnal variation of vigilance performance with normal circadian rhythms and the corresponding neural basis. With 34 healthy adults, we recorded the resting-state electroencephalogram activities and the following vigilance performance measured by psychomotor vigilance test in the morning, the no-nap mid afternoon, and the nap mid afternoon. The circadian process was controlled by measuring vigilance and resting-state electroencephalogram activities at the same time point in the nap and no-nap conditions. Homeostatic sleep pressure accumulated from morning to mid afternoon induced the declined vigilance performance and a global increase in resting-state delta, theta, alpha, and beta1 bands power, and a local increase in beta2 band power in the central region. Furthermore, the more the spontaneous beta2 power increased, the less vigilance declined from morning to mid afternoon. The current findings suggest that homeostatic sleep pressure increased cortical excitability but decreased cortical communication efficiency from morning to mid afternoon. In addition, the activity of the high beta waves probably reflected the compensatory effort to counteract the negative impact of the low arousal state on the following vigilance task by performing more action preparation in the no-nap afternoon.

Lateralized connectivity in the alpha band between parietal and occipital sources when spatial attention is externally and internally directed

IntroductionExternal spatial attention refers to the selection of currently present information at a specific external location, whereas internal spatial attention refers to the selection of stored information in short-term memory initially presented at a specific location. Electroencephalographic (EEG) and magnetoencephalographic (MEG) studies revealed that these two types of selection may involve the same underlying neural mechanism as in both cases a reduction in posterior alpha power was observed. However, the posterior alpha rhythm may consist of different components, which can even be related to opposite behavioral effects. Furthermore, the employed paradigms to study both selection processes are often quite different, which makes a proper comparison cumbersome.MethodsIn the current EEG experiment, two-stimulus displays were preceded or followed by non-spatial pre-cues and post-cues that specified the target, thereby minimizing procedural differences.ResultsResults of time-frequency analyses revealed that in both cue conditions the selection of relevant information was associated with an increase of ipsilateral vs. contralateral posterior alpha power. An opposite effect, an increase in contralateral vs. ipsilateral posterior power was observed in the theta-band, but only in the pre-cue condition. This activity was related to stimulus onset and likely reflects target selection. To assess attention-related connectivity, we separated posterior alpha power in a medial-parietal and two parieto-occipital sources and computed alpha phase coherence between these sources. Results revealed that in both cue conditions, increased ipsilateral vs. contralateral connectivity in the alpha band was present between the medial-parietal and parieto-occipital sources.DiscussionThe results seem to reflect a modulation from parietal to occipital areas, providing support for the view that internal and external spatial attention share a common neural mechanism.

Different oscillatory rhythms anticipate failures in executive and arousal vigilance

IntroductionVigilance is the challenging ability to maintain attention during long periods. When performing prolonged tasks, vigilance failures are often observed, reflecting a decrease in performance. Previous research has shown that changes in oscillatory rhythms are associated with states of vigilance loss. The present study aimed to investigate whether changes in different oscillatory rhythms anticipate failures in two vigilance components: (a) executive vigilance –necessary to detect infrequent critical signals– and (b) arousal vigilance –necessary to maintain a fast reaction to environmental stimuli without much control–.Methods37 young adults (age: M = 25.86; SD = 4.99) completed two experimental sessions in which high-density electroencephalography signal was recorded while they performed the Attentional Networks Test for Interactions and Vigilance – executive and arousal components, a task that simultaneously measures executive and arousal vigilance along with others attentional functions. Changes in delta, theta, alpha, beta, and gamma power before target onset were analyzed at the trial level in the executive and the arousal vigilance subtasks and as a function of the behavioral response.ResultsChanges in different oscillatory rhythms were observed prior to failures in executive and arousal vigilance. While increased alpha power in left occipital regions anticipated misses in the executive vigilance subtask, increased delta power in frontal-central regions anticipated very slow responses in the arousal vigilance subtask.DiscussionThe present results further support an empirical dissociation at the neural level between executive and arousal vigilance. Changes in alpha –in left occipital regions– and delta –in frontal-central regions– power might be identified as different brain states associated with loss in vigilance components when performing prolonged tasks.

Musical tempo affects EEG spectral dynamics during subsequent time estimation

The perception of time depends on the rhythmicity of internal and external synchronizers. One external synchronizer that affects time estimation is music. This study aimed to analyze the effects of musical tempi on EEG spectral dynamics during subsequent time estimation. Participants performed a time production task after (i) silence and (ii) listening to music at different tempi –90, 120, and 150 bpm– while EEG activity was recorded. While listening, there was an increase in alpha power at all tempi compared to the resting state and an increase of beta at the fastest tempo. The beta increase persisted during the subsequent time estimations, with higher beta power during the task after listening to music at the fastest tempo than task performance without music. Spectral dynamics in frontal regions showed lower alpha activity in the final stages of time estimations after listening to music at 90- and 120-bpm than in the silence condition and higher beta in the early stages at 150 bpm. Behaviorally, the 120 bpm musical tempo produced slight improvements. Listening to music modified tonic EEG activity that subsequently affected EEG dynamics during time production. Music at a more optimal rate could have benefited temporal expectation and anticipation. The fastest musical tempo may have generated an over-activated state that affected subsequent time estimations. These results emphasize the importance of music as an external stimulus that can affect brain functional organization during time perception even after listening.

EEG Features for Driver’s Mental Fatigue Detection: A Preliminary Work

Mental fatigue is one of the most typical human infirmities, resulting from an overload of work and lack of sleep which can reduce one’s intellectual resources. Different EEG features have been studied for detecting mental fatigue. This paper characterizes mental fatigue through the understanding of human EEG features for safe driving behaviour and to create an overview of the potential EEG features which are related to mental fatigue. A narrative review approach is employed for describing the neural activity of the human brain in mental fatigue. Specific EEG features in relation to driving tasks, relation to different EEG band waves, pre-processing and feature extraction methods are discussed. From this preliminary work, the increase of parietal alpha power seems to characterize the driver’s mental fatigue in most of the studies. We searched public EEG repositories for identifying potential data sources for our initial study. Finally, we propose a conceptual model that has potentials for identifying mental weariness. In conclusion, future works may involve the identification of other EEG features of higher importance for generalization across study conditions

Neuromapping olfactory stimulation using magnetoencephalography - visualizing smell, a proof-of-concept study.

Currently, clinical assessment of olfaction is largely reliant on subjective methods that require patient participation. The objective method for measuring olfaction, using electroencephalogram (EEG) readings, can be supplemented with the improved temporal resolution of magnetoencephalography (MEG) for olfactory measurement that can delineate cortical and peripheral olfactory loss. MEG provides high temporal and spatial resolution which can enhance our understanding of central olfactory processing compared to using EEG alone. To determine the feasibility of building an in-house portable olfactory stimulator paired with electrophysiological neuroimaging technique with MEG to assess olfaction in the clinical setting. This proof-of-concept study utilized a paired MEG-olfactometer paradigm to assess olfaction in three normosmic participants. We used a two-channel olfactory stimulator to deliver odorants according to a programmed stimulus-rest paradigm. Two synthetic odorants: 2% phenethyl alcohol (rose) and 0.5% amyl acetate (banana) were delivered in increasing increments of time followed by periods of rest. Cortical activity was measured via a 306-channel MEG system. Primary outcome measure was the relative spectral power for each frequency band, which was contrasted between rest and olfactory stimulation. Compared to rest, olfactory stimulation produced a 40% increase in relative alpha power within the olfactory cortex bilaterally with both odorants. A 25%-30% increase in relative alpha power occurred in the left orbitofrontal cortex and precentral gyrus with phenethyl alcohol stimulation but not amyl acetate. In this proof-of-concept study, we demonstrate the feasibility of olfactory measurement via an olfactometer-MEG paradigm. We found that odorant-specific cortical signatures can be identified using this paradigm, setting the basis for further investigation of this system as a prognostic tool for olfactory loss.

Attempting to counteract vigilance decrement in older adults with brain stimulation.

Against the background of demographic change and the need for enhancement techniques for an aging society, we set out to repeat a study that utilized 40-Hz transcranial alternating current stimulation (tACS) to counteract the slowdown of reaction times in a vigilance experiment but with participants aged 65 years and older. On an oscillatory level, vigilance decrement is linked to rising occipital alpha power, which has been shown to be downregulated using gamma-tACS. We applied tACS on the visual cortex and compared reaction times, error rates, and alpha power of a group stimulated with 40 Hz to a sham and a 5-Hz-stimulated control group. All groups executed two 30-min-long blocks of a visual task and were stimulated according to group in the second block. We hypothesized that the expected increase in reaction times and alpha power would be reduced in the 40-Hz group compared to the control groups in the second block (INTERVENTION). Statistical analysis with linear mixed models showed that reaction times increased significantly over time in the first block (BASELINE) with approximately 3 ms/min for the SHAM and 2 ms/min for the 5-Hz and 40-Hz groups, with no difference between the groups. The increase was less pronounced in the INTERVENTION block (1 ms/min for SHAM and 5-Hz groups, 3 ms/min for the 40-Hz group). Differences among groups in the INTERVENTION block were not significant if the 5-Hz or the 40-Hz group was used as the base group for the linear mixed model. Statistical analysis with a generalized linear mixed model showed that alpha power was significantly higher after the experiment (1.37 μV2) compared to before (1 μV2). No influence of stimulation (40 Hz, 5 Hz, or sham) could be detected. Although the literature has shown that tACS offers potential for older adults, our results indicate that findings from general studies cannot simply be transferred to an old-aged group. We suggest adjusting stimulation parameters to the neurophysiological features expected in this group. Next to heterogeneity and cognitive fitness, the influence of motivation and medication should be considered.

Exoskeleton Training Modulates Complexity in Movement Patterns and Cortical Activity in Able-Bodied Volunteers.

Robot-aided gait training (RAGT) plays a crucial role in providing high-dose and high-intensity task-oriented physical therapy. The human-robot interaction during RAGT remains technically challenging. To achieve this aim, it is necessary to quantify how RAGT impacts brain activity and motor learning. This work quantifies the neuromuscular effect induced by a single RAGT session in healthy middle-aged individuals. Electromyographic (EMG) and motion (IMU) data were recorded and processed during walking trials before and after RAGT. Electroencephalographic (EEG) data were recorded during rest before and after the entire walking session. Linear and nonlinear analyses detected changes in the walking pattern, paralleled by a modulation of cortical activity in the motor, attentive, and visual cortices immediately after RAGT. Increases in alpha and beta EEG spectral power and pattern regularity of the EEG match the increased regularity of body oscillations in the frontal plane, and the loss of alternating muscle activation during the gait cycle, when walking after a RAGT session. These preliminary results improve the understanding of human-machine interaction mechanisms and motor learning and may contribute to more efficient exoskeleton development for assisted walking.

Alpha power modulation with tACS: a customized therapeutic approach

Abstract Among other electrophysiological biomarkers, power reduction in the alpha frequency band (8-12 Hz) is characteristic of Alzheimer’s Disease (AD). Restoring power in this band could help improve the performance of related functional networks and the cognitive state in AD patients. Transcranial alternate current stimulation (tACS) stands as a promising tool in this regard, given its capacity to entrain neural activity at a particular frequency. 27 healthy participants with ages ranging from (22 to 55 years/ 32.80 ± 8.52 ) were recruited for this study. After being randomly assigned to verum or sham group, each participant was stimulated through tACS at the Cz and Oz electrodes at his own Individual Alpha Frequency (IAF) for 20 minutes. The neurophysiological activity of each participant was initially captured by two successive 5-minute eyes-closed resting state MEG recordings, with a 10-minute time interval between the two sessions. After stimulation, a third MEG recording was extracted to measure the effects. After performing the CBPT analysis, the tACS group showed an increase of alpha power in a cluster of bilateral frontal, temporal and occipital cortical sources (p<0.01). Research Category and Technology and Methods Clinical Research: 5. Other Transcranial Electrical Stimulation (tES) Keywords: tACS, MCI, Alfa, Neurostimulation

Alpha transcranial alternating current stimulation reduces depressive symptoms in people with schizophrenia and auditory hallucinations: a double-blind, randomized pilot clinical trial

People with schizophrenia exhibit reduced alpha oscillations and frontotemporal coordination of brain activity. Alpha oscillations are associated with top-down inhibition. Reduced alpha oscillations may fail to censor spurious endogenous activity, leading to auditory hallucinations. Transcranial alternating current stimulation (tACS) at the alpha frequency was shown to enhance alpha oscillations in people with schizophrenia and may thus be a network-based treatment for auditory hallucinations. We conducted a double-blind, randomized, placebo-controlled pilot clinical trial to examine the efficacy of 10-Hz tACS in treating auditory hallucinations in people with schizophrenia. 10-Hz tACS was administered in phase at the dorsolateral prefrontal cortex and the temporoparietal junction with a return current at Cz. Patients were randomized to receive tACS or sham for five consecutive days during the treatment week (40 min/day), followed by a maintenance period, during which participants received weekly tACS (40 min/visit) or sham. tACS treatment reduced general psychopathology (p < 0.05, Cohen’s d = −0.690), especially depression (p < 0.005, Cohen’s d = −0.806), but not auditory hallucinations. tACS treatment increased alpha power in the target region (p < 0.05), increased the frequency of peak global functional connectivity towards 10 Hz (p < 0.05), and reduced left-right frontal functional connectivity (p < 0.005). Importantly, changes in brain functional connectivity significantly correlated with symptom improvement (p < 0.05). Daily 10 Hz-tACS increased alpha power and altered alpha-band functional connectivity. Successful target engagement reduced depression and other general psychopathology symptoms, but not auditory hallucinations. Considering existing research of 10Hz tACS as a treatment for major depressive disorder, our study demonstrates its transdiagnostic potential for treating depression.

A Comparison of the Effects of Binaural Beats of Audible and Inaudible Frequencies on Brainwaves

The purpose of this study was to observe the effects of audible and inaudible binaural beat stimuli on alpha power elicitation and compare the differences in triggering effects depending on sound perception. Experiments were conducted on healthy male and female subjects (11 males and 10 females, mean age of 24.6 ± 1.8). To induce alpha waves, audible (250 Hz) or non-audible baseline sound frequencies (18,000 Hz) were presented to the left ear, and a frequency 10 Hz higher than the baseline was presented to the right ear. There were two experimental phases: a rest phase (5 min) in which no stimulus was presented and a stimulation phase (5 min) in which the binaural beat stimulus was presented. An electroencephalogram was measured at a sampling rate of 500 Hz, and relative alpha power values were calculated for each phase in each brain area. In the central regions, both baseline frequencies (audible and inaudible) increased the relative alpha power during the stimulation phase compared with the rest phase, and there were no differences between the two baseline frequencies. In the frontal and central regions, there was a greater increase in relative alpha power in the audible case compared with the inaudible case.

Toward Affirmation of Recovery of Deeply Embedded Autobiographical Memory with Background Music and Identification of an EEG Biomarker in Combination with EDA Signal Using Wearable Sensors

There is no disputing the role that background music plays in memory recall. Music has the power to activate the brain and trigger deeply ingrained memories. For dementia patients, background music is a common therapy because of this. Previous studies used music to recall lyrics, series of words, and long- and short-term memories. In this research, electroencephalogram (EEG) and electrodermal activity (EDA) data are collected from 40 healthy participants using wearable sensors during nine music sessions (three happy, three sad, and three neutral). A post-study survey is given to all participants after each piece of music to know if they recalled any autobiographical memories. The main objective is to find an EEG biomarker using the collected qualitative and quantitative data for autobiographical memory recall. The study finds that for all four EEG channels, alpha power rises considerably (on average 16.2%) during the memory “recall” scenario (F3: p = 0.0066, F7: p = 0.0386, F4: p = 0.0023, and F8: p = 0.0288) compared to the “no-recall” situation. Beta power also increased significantly for two channels (F3: p = 0.0100 and F4: p = 0.0210) but not for others (F7: p = 0.6792 and F8: p = 0.0814). Additionally, the phasic standard deviation (p = 0.0260), phasic max (p = 0.0011), phasic energy (p = 0.0478), tonic min (p = 0.0092), tonic standard deviation (p = 0.0171), and phasic energy (p = 0.0478) are significantly different for the EDA signal. The authors conclude by interpreting increased alpha power (8–12 Hz) as a biomarker for autobiographical memory recall.

Spectral signatures associated with cognitive aging, APOE4, amyloid‐β and measures of axonal integrity in cognitively unimpaired adults

AbstractBackgroundOscillatory brain rhythms are a defining feature of neuronal activity that support cognition in humans. Previous studies that showed associations of spectral changes in individuals who harbor high risk for Alzheimer’s disease (AD) were limited to identify abnormalities within select brain regions defined apriori. Comprehensive whole‐brain spatiotemporal patterns of oscillatory changes associated with cognitive‐aging and with AD risk are only partly known. Our main goals were to understand how frequency specific spectral changes relate to cognitive abilities in normal aging and to identify oscillatory signatures that indicate pre‐symptomatic AD pathophysiological processes in cognitively unimpaired elderly.MethodsWe used magnetoencephalography (MEG) to study the spectral signatures within delta‐theta (2‐7Hz), alpha (8‐12Hz) and beta (13‐35Hz) oscillations, in cognitively unimpaired adults (n=70). Using a partial‐least‐square regression, we correlated spectral patterns to executive, memory, and processing‐speed abilities (n=40). Next, we compared the spectral signatures between amyloid‐β (Aβ)+ vs. Aβ‐ and between APOE‐Ɛ4+ vs. APOE‐Ɛ4‐, in sub‐cohorts evaluated with Aβ‐PET (n=46) and APOE4 (n=65), respectively. In a subset of participants (n=19), we also examined associations between spectral signatures and cerebrospinal fluid (CSF) markers indicating damage to: presynaptic (growth‐associated protein‐43, GAP43); postsynaptic (neurogranin, NG); axonal (neurofilament light chain, NFL), levels.ResultsAn age dependent, low‐grade, increase in alpha power and decrease in delta‐theta power were associated with better cognitive performance in memory, executive and processing speed (Figure‐1). APOE4+ individuals showed reduced alpha power within bilateral medial temporal and right precuneus, compared to APOE4‐. Aβ+ individuals showed a dual pattern of alpha change with increased frontal and reduced medial and lateral temporal cortex pattern and a frontally distributed increased delta‐theta power (Figure‐2). Higher CSF‐NFL was correlated with lower alpha power.ConclusionsOur findings demonstrate that higher alpha power indicates a positive spectral change towards better cognitive health in aging. Importantly, a reduced alpha power signature indicated early neurodegenerative changes, as demonstrated by: (1)Aβ+ individuals and APOE‐Ɛ4+ individuals showing reduced alpha power within the regions known for earliest tau accumulations; (2) lower alpha correlating with higher NFL, which reflects Aβ‐independent neurodegeneration. Collectively alpha signatures may indicate tau related neuropathology with aging and in early AD.

Decreased Electroencephalographic Alpha Power During Anesthesia Induction Is Associated With EEG Discontinuity in Human Infants.

Electroencephalogram (EEG) discontinuity can occur at high concentrations of anesthetic drugs, reflecting suppression of electrocortical activity. This EEG pattern has been reported in children and reflects a deep state of anesthesia. Isoelectric events on the EEG, a more extreme degree of voltage suppression, have been shown to be associated with worse long-term neurologic outcomes in neonates undergoing cardiac surgery. However, the clinical significance of EEG discontinuities during pediatric anesthesia for noncardiac surgery is not yet known and merits further research. In this study, we assessed the incidence of EEG discontinuity during anesthesia induction in neurologically normal infants and the clinical factors associated with its development. We hypothesized that EEG discontinuity would be associated with sevoflurane-induced alpha (8-12 Hz) power during the period of anesthesia induction in infants. We prospectively recorded 26 channels of EEG during anesthesia induction in an observational cohort of 54 infants (median age, 7.6 months; interquartile range [IQR] [4.9-9.8 months]). We identified EEG discontinuity, defined as voltage amplitude <25 microvolts for >2 seconds, and assessed its association with sevoflurane-induced alpha power using spectral analysis and multivariable logistic regression adjusting for clinically important variables. EEG discontinuity was observed in 20 of 54 subjects (37%), with a total of 25 discrete events. Sevoflurane-induced alpha power in the posterior regions of the head (eg, parietal or occipital regions) was significantly lower in the EEG discontinuity group (midline parietal channel on the electroencephalogram, International 10-20 System [Pz]; 8.3 vs 11.2 decibels [dBs]; P = .004), and this association remained after multivariable adjustment (adjusted odds ratio [aOR] = 0.51 per dB increase in alpha power [95% CI, 0.30-0.89]; P = .02). There were no differences in the baseline (unanesthetized) EEG between groups in alpha power or power in any other frequency band. We demonstrate that EEG discontinuity is common during anesthesia induction and is related to the level of sevoflurane-induced posterior alpha power, a putative marker of cortical-thalamic circuit development in the first year of life. This association persisted even after adjusting for age and propofol coadministration. The fact that this difference was only observed during anesthesia and not in the baseline EEG suggests that otherwise hidden brain circuit properties are unmasked by general anesthesia. These neurophysiologic markers observed during anesthesia may be useful in identifying patients who may have a greater chance of developing discontinuity.