Beta Spectral Power Research Articles

Beta Spectral Power during Passive Listening in Preschool Children with Specific Language Impairment

Introduction: Children with specific language impairment (SLI) have difficulties in different speech and language domains. Electrophysiological studies have documented that auditory processing in children with SLI is atypical and probably caused by delayed and abnormal auditory maturation. During the resting state, or different auditory tasks, children with SLI show low or high beta spectral power, which could be a clinical correlate for investigating brain rhythms. Methods: The aim of this study was to examine the electrophysiological cortical activity of the beta rhythm while listening to words and nonwords in children with SLI in comparison to typical development (TD) children. The participants were 50 children with SLI, aged 4 and 5 years, and 50 age matched TD children. The children were divided into two subgroups according to age: (1) children 4 years of age; (2) children 5 years of age. Results: The older group differed from the younger group in beta auditory processing, with increased values of beta spectral power in the right frontal, temporal, and parietal regions. In addition, children with SLI have higher beta spectral power than TD children in the bilateral temporal regions. Conclusion: Complex beta auditory activation in TD and SLI children indicates the presence of early changes in functional brain connectivity.

Bright light therapy and early morning attention, mathematical performance, electroencephalography and brain connectivity in adolescents with morning sleepiness.

Adolescents typically sleep too little and feel drowsy during morning classes. We assessed whether morning use of an LED bright light device could increase alertness in school students. Twenty-six (8M/18F) healthy, unmedicated participants, ages 13-18 years, (mean 17.1±1.4) were recruited following screenings to exclude psychopathology. Baseline assessments were made of actigraph-assessed sleep, attention, math solving ability, electroencephalography and structural and functional MRI (N = 10-11, pre-post). Participants nonrandomly received 3-4 weeks of bright light therapy (BLT) for 30 minutes each morning and used blue light blocking glasses for 2 hours before bedtime. BLT devices were modified to surreptitiously record degree of use so that the hypothesis tested was whether there was a significant relationship between degree of use and outcome. They were used 57±18% (range 23%-90%) of recommended time. There was a significant association between degree of use and: (1) increased beta spectral power in frontal EEG leads (primary measure); (2) greater post-test improvement in math performance and reduction in errors of omission on attention test; (3) reduced day-to-day variability in bed times, sleep onset, and sleep duration during school days; (4) increased dentate gyrus volume and (5) enhanced frontal connectivity with temporal, occipital and cerebellar regions during Go/No-Go task performance. BLT was associated with improvement in sleep cycle consistency, arousal, attention and functional connectivity, but not sleep onset or duration (primary measures). Although this was an open study, it suggests that use of bright morning light and blue light blocking glasses before bed may benefit adolescents experiencing daytime sleepiness. Clinical trial registration: Clinicaltrials.gov ID-NCT05383690.

Beta spectral power during sleep is associated with impaired recall of extinguished fear.

The failure to retain memory for extinguished fear plays a major role in the maintenance of posttraumatic stress disorder (PTSD), with successful extinction recall necessary for symptom reduction. Disturbed sleep, a hallmark symptom of PTSD, impairs fear extinction recall. However, our understanding of the electrophysiological mechanisms underpinning sleep's role in extinction retention remains underdetermined. We examined the relationship between the microarchitecture of sleep and extinction recall in healthy humans (n = 71, both male and females included) and a pilot study in individuals with PTSD (n = 12). Participants underwent a fear conditioning and extinction protocol over 2 days, with sleep recording occurring between conditioning and extinction. Twenty-four hours after extinction learning, participants underwent extinction recall. Power spectral density (PSD) was computed for pre- and post-extinction learning sleep. Increased beta-band PSD (~17-26 Hz) during pre-extinction learning sleep was associated with worse extinction recall in healthy participants (r = 0.41, p = .004). Beta PSD was highly stable across three nights of sleep (intraclass correlation coefficients > 0.92). Results suggest beta-band PSD is specifically implicated in difficulties recalling extinguished fear.

Blink-related EEG oscillations are neurophysiological indicators of subconcussive head impacts in female soccer players: a preliminary study.

Repetitive subconcussive head impacts can lead to subtle neural changes and functional consequences on brain health. However, the objective assessment of these changes remains limited. Resting state blink-related oscillations (BROs), recently discovered neurological responses following spontaneous blinking, are explored in this study to evaluate changes in BRO responses in subconcussive head impacts. We collected 5-min resting-state electroencephalography (EEG) data from two cohorts of collegiate athletes who were engaged in contact sports (SC) or non-contact sports (HC). Video recordings of all on-field activities were conducted to determine the number of head impacts during games and practices in the SC group. In both groups, we were able to detect a BRO response. Following one season of games and practice, we found a strong association between the number of head impacts sustained by the SC group and increases in delta and beta spectral power post-blink. There was also a significant difference between the two groups in the morphology of BRO responses, including decreased peak-to-peak amplitude of response over left parietal channels and differences in spectral power in delta and alpha frequency range post-blink. Our preliminary results suggest that the BRO response may be a useful biomarker for detecting subtle neural changes resulting from repetitive head impacts. The clinical utility of this biomarker will need to be validated through further research with larger sample sizes, involving both male and female participants, using a longitudinal design.

A Pilot Investigation Evaluating Relative Changes in Fronto-Occipital Alpha and Beta Spectral Power as Measurement of Anesthesia Hypnotic Depth.

Other than clinical observation of a patient's vegetative response to nociception, monitoring the hypnotic component of general anesthesia (GA) and unconsciousness relies on electroencephalography (EEG)-based indices. These indices exclusively based on frontal EEG activity neglect an important observation. One of the main hallmarks of transitions from wakefulness to GA is a shift in alpha oscillations (7.5-12.5 Hz activity) from occipital brain regions toward anterior brain regions ("alpha anteriorization"). Monitoring the degree of this alpha anteriorization may help to guide induction and maintenance of hypnotic depth and prevent intraoperative awareness. However, the occipital region of the brain is completely disregarded and occipital alpha as characteristic of wakefulness and its posterior-to-anterior shift during induction are missed. Here, we propose an application of Narcotrend's reduced power alpha beta (RPAB) index, originally developed to monitor differences in hemispheric perfusion, for determining the ratio of alpha and beta activity in the anterior-posterior axis. Perioperative EEG data of 32 patients undergoing GA in the ophthalmic surgery department of Bern University Hospital were retrospectively analyzed. EEG was recorded with the Narcotrend® monitor using a frontal (Fp1-Fp2) and a posterior (T9-Oz) bipolar derivation with reference electrode over A2. The RPAB index was computed between both bipolar signals, defining the fronto-occipital RPAB (FO-RPAB). FO-RPAB was analyzed during wakefulness, GA maintenance, and emergence, as well as before and after the intraoperative administration of a ketamine bolus. FO-RPAB was compared with a classical quantitative EEG measure-the spectral edge frequency 95% (SEF-95). A significant shift of the FO-RPAB was observed during both induction of and emergence from GA ( P < .001). Interestingly, the additional administration of ketamine during GA did not lead to a significant change in FO-RPAB ( P = 0.81). In contrast, a significant increase in the SEF-95 in the frontal channel was observed during the 10-minute period after ketamine administration ( P < .001). FO-RPAB appears to qualify as a marker of unconsciousness, reflecting physiological fronto-occipital activity differences during GA. In contrast to frontal SEF-95, it is not disturbed by additional administration of ketamine for analgesia.

Multi-modal investigation of transcranial ultrasound-induced neuroplasticity of the human motor cortex

IntroductionThere is currently a gap in accessibility to neuromodulation tools that can approximate the efficacy and spatial resolution of invasive methods. Low intensity transcranial focused ultrasound stimulation (TUS) is an emerging technology for non-invasive brain stimulation (NIBS) that can penetrate cortical and deep brain structures with more focal stimulation compared to existing NIBS modalities. Theta burst TUS (tbTUS, TUS delivered in a theta burst pattern) is a novel repetitive TUS protocol that can induce durable changes in motor cortex excitability, thereby holding promise as a novel neuromodulation tool with durable effects. ObjectiveThe aim of the present study was to elucidate the neurophysiologic effects of tbTUS motor cortical excitability, as well on local and global neural oscillations and network connectivity. MethodsAn 80-s train of active or sham tbTUS was delivered to the left motor cortex in 15 healthy subjects. Motor cortical excitability was investigated through transcranial magnetic stimulation (TMS)-elicited motor-evoked potentials (MEPs), short-interval intracortical inhibition (SICI), and intracortical facilitation (ICF) using paired-pulse TMS. Magnetoencephalography (MEG) recordings during resting state and an index finger abduction-adduction task were used to assess oscillatory brain responses and network connectivity. The correlations between the changes in neural oscillations and motor cortical excitability were also evaluated. ResultstbTUS to the motor cortex results in a sustained increase in MEP amplitude and decreased SICI, but no change in ICF. MEG spectral power analysis revealed TUS-mediated desynchronization in alpha and beta spectral power. Significant changes in alpha power were detected within the supplementary motor cortex (Right > Left) and changes in beta power within bilateral supplementary motor cortices, right basal ganglia and parietal regions. Coherence analysis revealed increased local connectivity in motor areas. MEP and SICI changes correlated with both local and inter-regional coherence. ConclusionThe findings from this study provide novel insights into the neurophysiologic basis of TUS-mediated neuroplasticity and point to the involvement of regions within the motor network in mediating this sustained response. Future studies may further characterize the durability of TUS-mediated neuroplasticity and its clinical applications as a neuromodulation strategy for neurological and psychiatric disorders.

Sleep Power Spectral Density and Spindles in PTSD and Their Relationship to Symptom Severity.

Sleep disturbances are common in post-traumatic stress disorder (PTSD), although which sleep microarchitectural characteristics reliably classify those with and without PTSD remains equivocal. Here, we investigated sleep microarchitectural differences (i.e., spectral power, spindle activity) in trauma-exposed individuals that met (n = 45) or did not meet (n = 52) criteria for PTSD and how these differences relate to post-traumatic and related psychopathological symptoms. Using ecologically-relevant home sleep polysomnography recordings, we show that individuals with PTSD exhibit decreased beta spectral power during NREM sleep and increased fast sleep spindle peak frequencies. Contrary to prior reports, spectral power in the beta frequency range (20.31–29.88 Hz) was associated with reduced PTSD symptoms, reduced depression, anxiety and stress and greater subjective ability to regulate emotions. Increased fast frequency spindle activity was not associated with individual differences in psychopathology. Our findings may suggest an adaptive role for beta power during sleep in individuals exposed to a trauma, potentially conferring resilience. Further, we add to a growing body of evidence that spindle activity may be an important biomarker for studying PTSD pathophysiology.

Prefrontal Physiomarkers of Anxiety and Depression in Parkinson's Disease.

Objective: Anxiety and depression are prominent non-motor symptoms of Parkinson’s disease (PD), but their pathophysiology remains unclear. We sought to understand their neurophysiological correlates from chronic invasive recordings of the prefrontal cortex (PFC).Methods: We studied four patients undergoing deep brain stimulation (DBS) for their motor signs, who had comorbid mild to moderate anxiety and/or depressive symptoms. In addition to their basal ganglia leads, we placed a permanent prefrontal subdural 4-contact lead. These electrodes were attached to an investigational pulse generator with the capability to sense and store field potential signals, as well as deliver therapeutic neurostimulation. At regular intervals over 3–5 months, participants paired brief invasive neural recordings with self-ratings of symptoms related to depression and anxiety.Results: Mean age was 61 ± 7 years, mean disease duration was 11 ± 8 years and a mean Unified Parkinson’s Disease Rating Scale, with part III (UPDRS-III) off medication score of 37 ± 13. Mean Beck Depression Inventory (BDI) score was 14 ± 5 and Beck Anxiety Index was 16.5 ± 5. Prefrontal cortex spectral power in the beta band correlated with patient self-ratings of symptoms of depression and anxiety, with r-values between 0.31 and 0.48. Mood scores showed negative correlation with beta spectral power in lateral locations, and positive correlation with beta spectral power in a mesial recording location, consistent with the dichotomous organization of reward networks in PFC.Interpretation: These findings suggest a physiological basis for anxiety and depression in PD, which may be useful in the development of neurostimulation paradigms for these non-motor disease features.

Associations of Hyperactivity and Inattention Scores with Theta and Beta Oscillatory Dynamics of EEG in Stop-Signal Task in Healthy Children 7-10 Years Old.

Simple SummaryMost studies on ADHD have been focused on the comparisons between healthy subjects and clinical patients. The dimensional approaches propose that the main pathological behavioral domains are distributed in the normal population and not only in individual categories of people (as assumed in traditional schemes of comparisons between patients and controls). In the current study, we used a similar approach to identify potential markers of ADHD by studying the EEG dynamics of healthy children with a natural variability in hyperactivity and inattention scores during performance of the Stop-Signal task. We found that hyperactivity/inattention scores were positively associated with RT variability. Hyperactivity/inattention scores were negatively associated with an increase in beta spectral power in the first 200 ms and positively associated with an increase in theta rhythm at about 300 ms after presentation of the Go stimulus. It has been hypothesized that such results imply insufficient vigilance in the early stages of perception and subsequent compensatory enhancing of attention to the stimulus in children with higher hyperactivity and inattention scores.In the current study, we aimed to investigate the associations between the natural variability in hyperactivity and inattention scores, as well as their combination with EEG oscillatory responses in the Stop-Signal task in a sample of healthy children. During performance, the Stop-Signal task EEGs were recorded in 94 Caucasian children (40 girls) from 7 to 10 years. Hyperactivity/inattention and inattention scores positively correlated with RT variability. Hyperactivity/inattention and inattention scores negatively correlated with an increase in beta spectral power in the first 200 ms after presentation of the Go stimulus. Such results are in line with the lack of arousal model in ADHD children and can be associated with less sensory arousal in the early stages of perception in children with symptoms of inattention. The subsequent greater increase in theta rhythm at about 300 ms after presentation of the Go stimulus in children with higher inattention scores may be associated with increased attention processes and compensation for insufficient vigilance in the early stages of perception.

The Dynamic Relationship Between Alpha and Beta Power and Next-Day Suicidal Ideation in Individuals With Treatment-Resistant Depression

BackgroundNocturnal wakefulness has emerged as a potential predictor of short-term suicide risk. This analysis used dynamic temporal patterns in alpha and beta power and global sleep metrics to explore the possible link between next-day suicidal ideation (NDSI) and wakefulness measures in unmedicated participants with treatment-resistant depression. MethodsThirty-three medication-free participants with treatment-resistant depression completed overnight polysomnography. Alpha and beta spectral power as functions over time were used to represent arousal-related components of the dynamic sleep process. A functional data analytic approach (multilevel functional principal component analysis [MFPCA]) was used to preserve the oscillatory nature of the data; MFPCA PC scores were then associated with NDSI. Associations between NDSI and polysomnography-defined wakefulness after sleep onset, sleep efficiency, and total sleep time were also evaluated. ResultsNDSI had the strongest relationship with the second beta PC score (slope = 0.09 [90% credible interval, 0.03 to 0.14]), which represented an oscillating pattern that reflected disturbed sleep. The first PCs from both alpha and beta MFPCAs represented the overall magnitude of power and were most closely associated with traditional polysomnography metrics but were not related to NDSI. Results were equivocal for wakefulness after sleep onset with NDSI and did not support a relationship between NDSI and either sleep efficiency or total sleep time, highlighting the value of information contained in oscillating electroencephalogram patterns for identifying physiological links between nocturnal wakefulness and NDSI. ConclusionsThis study leveraged the dynamic nature of wakefulness-related electroencephalogram frequencies and provides a potential electrophysiological link between suicidal ideation and wakefulness during sleep in individuals with treatment-resistant depression.

Task-specific interhemispheric hypoconnectivity in writer’s cramp – An EEG study

ObjectiveWriter’s cramp (WC) is a focal task-specific dystonia characterized by abnormal posturing of the hand muscles during handwriting, but not during other tasks that involve the same set of muscles and objects such as sharpening a pencil. Our objective was to investigate the pathophysiology underlying the task specificity of this disorder using EEG. We hypothesized that premotor-parietal connectivity will be lower in WC patients specifically during handwriting and motor imagery of handwriting. MethodsWe recruited 15 WC patients and 15 healthy controls. EEG was recorded while participants performed 4 tasks – writing with a pencil, sharpening a pencil, imagining writing and imagining sharpening. We determined the connectivity changes between relevant brain regions during these tasks. ResultsWe found reduced interhemispheric alpha coherence in the sensorimotor areas in WC patients exclusively during handwriting. WC patients also showed less reduction of task-related beta spectral power and a trend for reduced premotor-parietal coherence during motor tasks. ConclusionWe could not confirm an abnormality in premotor-parietal connectivity specific to handwriting by this method. However, there was a task-specific reduction in interhemispheric alpha connectivity in WC patients, whose behavioral correlate remains unknown. SignificanceInterhemispheric alpha connectivity can be a potential interventional target in WC.

Resting State Quantitative Electroencephalogram Power Spectra in Patients with Depressive Disorder as Compared to Normal Controls: An Observational Study.

Introduction:A significant number of quantitative electroencephalogram (qEEG) studies indicate that increased spectral activities distinguish patients with depressive disorder from control subjects. But they did not yield consistent findings in the delta, theta, alpha, or beta bands.Methods:A total of 30 drug-naïve or drug-free subjects with a depressive episode or recurrent depressive disorder were compared with 30 age, sex, education, and handedness-matched healthy controls using qEEG power spectra in six frequency bands (delta, theta, alpha, beta, slow beta, and fast beta) and total activities separately. Spectral analysis was performed on a section of 180 s of qEEG digitized at the rate of 512 samples/s/channel, and absolute powers were log-transformed before statistical analysis.Results:Statistically significant differences between the patients and normal controls were found in the delta and the total bands, while Structured Interview Guide for the Hamilton Depression Rating Scale ( SIGH-D) score predicted the fast beta spectral power at the left temporal region. In the entire region of the brain, in the theta band, lesser absolute spectral power was found in patients than normal controls, whereas in the fast beta band, it was greater. In other bands, greater powers of spectral activities were found in patients than normal controls consistently in the parietal and occipital regions.Conclusion:Various findings of qEEG absolute power spectra could demonstrate a difference between the patients with depressive disorder and the normal controls independently and efficiently. However, all the differences collectively showed stronger evidence. The findings may steer future studies to differentiate the patients with depressive disorder from controls.

Faster Gait Speeds Reduce Alpha and Beta EEG Spectral Power From Human Sensorimotor Cortex.

ObjectiveOur aim was to determine if walking speed affected human sensorimotor electrocortical dynamics using mobile high-density electroencephalography (EEG).MethodsTo overcome limitations associated with motion and muscle artifact contamination in EEG recordings, we compared solutions for artifact removal using novel dual layer EEG electrodes and alternative signal processing methods. Dual layer EEG simultaneously recorded human electrocortical signals and isolated motion artifacts using pairs of mechanically coupled and electrically independent electrodes. For electrical muscle activity removal, we incorporated electromyographic (EMG) recordings from the neck into our mobile EEG data processing pipeline. We compared artifact removal methods during treadmill walking at four speeds (0.5, 1.0, 1.5, and 2.0 m/s).ResultsLeft and right sensorimotor alpha and beta spectral power increased in contralateral limb single support and push off, and decreased during contralateral limb swing at each speed. At faster walking speeds, sensorimotor spectral power fluctuations were less pronounced across the gait cycle with reduced alpha and beta power (p<0.05) compared to slower speeds. Isolated noise recordings and neck EMG spectral power fluctuations matched gait events and showed broadband spectral power increases at faster speeds.Conclusion and significanceDual layer EEG enabled us to isolate changes in human sensorimotor electrocortical dynamics across walking speeds. A comparison of signal processing approaches revealed similar intrastride cortical fluctuations when applying common (e.g. Artifact Subspace Reconstruction) and novel artifact rejection methods. Dual layer EEG, however, allowed us to document and rule out residual artifacts, which exposed sensorimotor spectral power changes across gait speeds.

EEG dynamics of spontaneous stimulus-independent thoughts

ABSTRACTIn this study, we aimed to compare the oscillatory dynamics accompanying self-referential and non-self-referential stimulus-independent thoughts. Electroencephalograms were recorded in 30 healthy participants who were asked to press buttons classifying their spontaneous thoughts as self-referential or non-self-referential. EEG data were analyzed using independent component analysis in conjunction with dipole localization. Self-referential thoughts, as compared to non-self-referential thoughts, were accompanied by more pronounced decreases of theta, alpha, and beta spectral power in the anterior hub of the default-mode network, in the left lateral prefrontal, motor/somatosensory, and temporal cortices. These oscillatory dynamics are interpreted as a reflection of autobiographical memory retrieval intrinsic to self-referential thoughts.Abbreviations: BA: Brodmann area; BOLD: blood oxygenation level-dependent; DMN: default mode network; EEG: electroencephalogram; ERSP: event-related spectral perturbations; fMRI: functional magnetic resonance imaging; PCC: posterior cingulate cortex; PET: positron emission tomography; PFC: prefrontal cortex; SIT: stimulus-independent thought; WM: working memory.

Spectral analysis highlight developmental EEG changes in preterm infants without overt brain damage

Early markers of neurological outcome in the absence of overt brain damage are scarce in extreme prematurity. The aim of this study was to compare spectral EEG values of infants born near term with those of infants born at extremely low gestational age (ELGA) but having attained near term age. We aimed also to evaluate whether spectral EEG features were related with neurological outcome. The ELGA group consisted of 12 neonates born between 23+2 and 27+6 weeks; the control group consisted of nine infants born 34–35+2 weeks, tested within the first week of life. All neonates underwent multichannel EEG recordings at 35 weeks post-conception. None of the subjects had apparent neurological abnormalities or risk factors at the time of recording. EEG data were transformed into the frequency domain and divided into delta (0.5–4Hz), theta (5–7Hz), alpha (8–13Hz), beta (14–20Hz) frequency bands; relative EEG power values were calculated. ELGA group was compared with the control group using a mixed analysis of variance. Outcome was evaluated at one year of age by Griffiths’ scales. A principal effect of frequency and an interaction effect of frequency * group was found. The total relative power of the delta band was significantly higher in ELGA than in control group, whereas in the remaining frequency bands total relative power was lower in ELGA than in control group. Higher values of delta and lower values of alpha and beta spectral power correlated with poor outcome. We provide preliminary results suggesting that, as early as 35 weeks post conception, infants born extremely preterm fail to develop the age specific pattern of EEG spectral activity, in the absence of neurological neonatal risk.

Task-related activity in sensorimotor cortex in Parkinson's disease and essential tremor: changes in beta and gamma bands.

In Parkinson's disease patients in the OFF medication state, basal ganglia local field potentials exhibit changes in beta and gamma oscillations that correlate with reduced voluntary movement, manifested as rigidity and akinesia. However, magnetoencephalography and low-resolution electrocorticography (ECoG) studies in Parkinson's patients suggest that changes in sensorimotor cortical oscillations differ from those of the basal ganglia. To more clearly define the role of sensorimotor cortex oscillatory activity in Parkinson's, we performed intraoperative, high-resolution (4 mm spacing) ECoG recordings in 10 Parkinson's patients (2 females, ages 47–72) undergoing deep brain stimulation (DBS) lead placement in the awake, OFF medication state. We analyzed ECoG potentials during a computer-controlled reaching task designed to separate movement preparation from movement execution and compared findings to similar invasive recordings in eight patients with essential tremor (3 females, ages 59–78), a condition not associated with rigidity or akinesia. We show that (1) cortical beta spectral power at rest does not differ between Parkinson's and essential tremor patients (p = 0.85), (2) early motor preparation in Parkinson's patients in the OFF medication state is associated with a larger beta desynchronization compared to patients with essential tremor (p = 0.0061), and (3) cortical broadband gamma power is elevated in Parkinson's patients compared to essential tremor patients during both rest and task recordings (p = 0.004). Our findings suggest an oscillatory profile in sensorimotor cortex of Parkinson's patients that, in contrast to the basal ganglia, may act to promote movement to oppose the anti-kinetic bias of the dopamine-depleted state.

Memory load effect in auditory-verbal short-term memory task: EEG fractal and spectral analysis.

The objective of this preliminary study was to quantify changes in complexity of EEG using fractal dimension (FD) alongside linear methods of spectral power, event-related spectral perturbations, coherence, and source localization of EEG generators for theta (4-7 Hz), alpha (8-12 Hz), and beta (13-23 Hz) frequency bands due to a memory load effect in an auditory-verbal short-term memory (AVSTM) task for words. We examined 20 healthy individuals using the Sternberg's paradigm with increasing memory load (three, five, and seven words). The stimuli were four-letter words. Artifact-free 5-s EEG segments during retention period were analyzed. The most significant finding was the increase in FD with the increase in memory load in temporal regions T3 and T4, and in parietal region Pz, while decrease in FD with increase in memory load was registered in frontal midline region Fz. Results point to increase in frontal midline (Fz) theta spectral power, decrease in alpha spectral power in parietal region-Pz, and increase in beta spectral power in T3 and T4 region with increase in memory load. Decrease in theta coherence within right hemisphere due to memory load was obtained. Alpha coherence increased in posterior regions with anterior decrease. Beta coherence increased in fronto-temporal regions. Source localization delineated theta activity increase in frontal midline region, alpha decrease in superior parietal region, and beta increase in superior temporal gyrus with increase in memory load. In conclusion, FD as a nonlinear measure may serve as a sensitive index for quantifying dynamical changes in EEG signals during AVSTM tasks.

Stability-dependent behavioural and electro-cortical reorganizations during intentional switching between bimanual tapping modes

This study investigated behavioural and electro-cortical reorganizations accompanying intentional switching between two distinct bimanual coordination tapping modes (In-phase and Anti-phase) that differ in stability when produced at the same movement rate. We expected that switching to a less stable tapping mode (In-to-Anti switching) would lead to larger behavioural perturbations and require supplementary neural resources than switching to a more stable tapping mode (Anti-to-In switching). Behavioural results confirmed that the In-to-Anti switching lasted longer than the Anti-to-In switching. A general increase in attention-related neural activity was found at the moment of switching for both conditions. Additionally, two condition-dependent EEG reorganizations were observed. First, a specific increase in cortico-cortical coherence appeared exclusively during the In-to-Anti switching. This result may reflect a strengthening in inter-regional communication in order to engage in the subsequent, less stable, tapping mode. Second, a decrease in motor-related neural activity (increased beta spectral power) was found for the Anti-to-In switching only. The latter effect may reflect the interruption of the previous, less stable, tapping mode. Given that previous results on spontaneous Anti-to-In switching revealing an inverse pattern of EEG reorganization (decreased beta spectral power), present findings give new insight on the stability-dependent neural correlates of intentional motor switching.

Electroencephalographic correlates of Chronic Fatigue Syndrome

BackgroundUnremitting fatigue and unrefreshing sleep, hallmark traits of Chronic Fatigue Syndrome (CFS), are also pathognomonic of sleep disorders. Yet, no reproducible perturbations of sleep architecture, multiple sleep latency times or Epworth Sleepiness Scores are found to be associated consistently with CFS. This led us to hypothesize that sleep homeostasis, rather than sleep architecture, may be perturbed in CFS. To probe this hypothesis, we measured and compared EEG frequencies associated with restorative sleep between persons with CFS and matched controls, both derived from a population-based sample.MethodsWe evaluated overnight polysomnography (PSG) in 35 CFS and 40 control subjects. PSG records were manually scored and epochs containing artifact removed. Fast Fourier Transformation was utilized to deconstruct individual EEG signals into primary frequency bands of alpha, delta, theta, sigma, and beta frequency domains. The spectral power of each frequency domain for each sleep state was compared between persons with CFS and matched controls.ResultsIn persons with CFS, delta power was diminished during slow wave sleep, but elevated during both stage 1 and REM. Alpha power was reduced during stage 2, slow wave, and REM sleep. Those with CFS also had significantly lower theta, sigma, and beta spectral power during stage 2, Slow Wave Sleep, and REM.DiscussionEmploying quantitative EEG analysis we demonstrate reduced spectral power of cortical delta activity during SWS. We also establish reduced spectral power of cortical alpha activity, with the greatest reduction occurring during REM sleep. Reductions in theta, beta, and sigma spectral power were also apparent.ConclusionUnremitting fatigue and unrefreshing sleep, the waking manifestations of CFS, may be the consequence of impaired sleep homeostasis rather than a primary sleep disorder.

Modulation of beta-range oscillatory synchrony as a mechanism for response selection

Event Abstract Back to Event Modulation of beta-range oscillatory synchrony as a mechanism for response selection Peter Praamstra1*, B C M Van Wijk2 and A. Daffertshofer2 1 Behavioural Brain Science Centre, University of Birmingham, United Kingdom 2 Research Institute MOVE, VU University Amsterdam, Netherlands Beta range oscillatory activity recorded over the motor cortex is typically attenuated during the preparation of movement and shows a rebound after movement. Contrasting with down-regulation before voluntary movement, recent work has demonstrated that beta activity can be prospectively up-regulated when the task requires a maintained posture instead of the generation of a new movement . Likewise, in the domain of visual spatial attention there is evidence for prospective up- and down-regulation of activity in the alpha frequency band. Both these examples concern anticipatory adjustments of oscillatory activity for future events. The present investigation addressed whether concurrent up- and down-regulation of beta synchrony can act as an online mechanism implementing the selection between competing motor responses. The investigation used high-density EEG and examined both local oscillatory synchrony (beta spectral power) and long-range oscillatory synchrony in terms of corticomuscular coherence and phase synchrony. Electroencephalographic and electromyographic signals were recorded during a cued choice reaction task. Response alternatives were mapped onto opposite hands and response readiness was manipulated by directional cues that were predictive or non-predictive of the response side indicated by an upcoming response signal. Reaction times and movement-related potentials confirmed that participants used the predictive cues to prepare their response. Further analyses focused on measures of beta activity during the two-second delay period, that is, during the interval between cue and response signal. In the first second of that period, directional cues elicited lateralized power, corticospinal coherence, and phase synchronization irrespective of their predictive value. At the same time, beta activity increased in the non-predictive cue condition relative to the predictive condition. By contrast, only predictive cues resulted in response preparation during the second half of the delay period, expressed in lateralization of not only power, but also of corticospinal coherence and phase synchronization. Together, these data indicate that processing of a directional cue, whether relevant or not, is associated with covert response activation, expressed in a differential modulation of beta activity in ipsi- and contralateral motor cortex. In addition, access of this covert activation to later preparation stages seems critically influenced by beta local and long-range synchrony. We therefore conclude that up- and down-regulation of beta activity is likely to have a functional role in response selection, resembling attentional modulation of alpha activity in visual selection.