Beta Range Research Articles

P106. Anodal tDCS over the left sensorimotor area improves motor symptoms and modulates corticocortical coherence in Parkinson’s disease

Network activity in the beta range is correlated with motor symptoms in Parkinson’s disease (PD). Anodal transcranial direct current stimulation (atDCS) over the sensorimotor area modulates cortical excitability and may alleviate motor symptoms in PD. In this study, we aimed to explore the effect of atDCS over the left sensorimotor area on clinical motor outcome, right hand fine motor performance and cortical motor network connectivity. In this double-blind randomized sham-controlled combined EEG and tDCS study, we investigated ten pharmacologically treated idiopathic PD patients after overnight withdrawal of dopaminergic medication and eleven healthy controls during an isometric precision grip task of the right hand before and after stimulation. Participants were studied and crossed-over in two sessions on different days with either ‘verum’ or ‘sham’ stimulation of atDCS (20 min; 1 mA; electrodes placed over left ‘C3’ (anode) and right ‘Fp2’ (cathode)). Cortical connectivity was expressed as corticocortical imaginary coherence in the high beta band (22–27 Hz) between ‘C3’ and all other EEG-channels; the topographic distribution was obtained from 25 cortical EEG channels placed according to the 10–20 system. Fine motor performance was expressed as accuracy error during the precision grip task with lower accuracy error indicating higher motor precision. Clinical motor outcome was measured using the UPDRS III motor score. PD patients with ‘verum’ stimulation showed an increase of corticocortical imaginary coherence in the high beta band from ‘C3’ to the right motor area 30 min after stimulation. This was paralleled by a significant decrease in the UPDRS III motor score. There was no similar modulation in PD ‘sham’ stimulation and in healthy controls in both ‘verum’ and ‘sham’ conditions. However, interestingly, HC showed beta band coupling prior to stimulation directed from ‘C3’ to the right hemisphere. Both groups showed no significant change regarding the accuracy error after stimulation. AtDCS of ‘C3’ entrains beta band coupling between ‘C3’ and the right sensorimotor area with ‘C3’ leading right hemispheric beta band oscillations in the temporal domain. We speculate that this could represent a mechanism to tone down inhibitory influences of the right hemisphere ipsilateral to the right hand, given that increased beta synchrony is associated with increasing motor inhibition in previous studies.

ОСОБЕННОСТИ БИОЭЛЕКТРИЧЕСКОЙ АКТИВНОСТИ ГОЛОВНОГО МОЗГА СТУДЕНТОК ВЫПУСКНОГО КУРСА В ЗАВИСИМОСТИ ОТ ИХ УРОВНЯ ТРЕВОЖНОСТИ

Aim. This article deals with the assessment of the bioelectric activity of the brain in finalyear female students depending on their anxiety level. Materials and methods. The study involved 32 final-year female students in the intersession period and 24 female students in the session period. The amplitude, frequency and EEG rhythm index were established using EEG spectral analysis. We also used the coherent analysis of EEG to reveal connections between different areas of the brain. Results. Higher situational anxiety is characterized by the increased coherence and decreased amplitude of alpha and theta rhythm. The analysis of EEG frequencies demonstrated the differences between the intersession and session periods only for a theta range. Theta activity dominated in female students with lower personal anxiety. In the session period in comparison with the intersession period we registered the highest values of theta rhythm in the frontal lobes in female students with high personal anxiety. Increased coherence was registered mainly in fronto-central and centro-temporal areas of the right hemisphere. In participants with low situational anxiety we established decreased coherence in the left temporal area for alpha rhythm and in the right fronto-central and left fronto-temporal areas for beta rhythm. In the intersession period in girls with low situational anxiety we registered decreased coherence in the left parieto-occipital, left fronto-parietal and right fronto-temporal areas for a beta range and in the right fronto-parietal area for theta rhythm. The most significant theta activity was registered in students with moderate personal anxiety in upper-frontal, central, left parietal, left occipital and right lower frontal areas. Conclusions. For the majority of female students low situational and high personal anxiety were typical for intersession and session periods. Girls with low situational anxiety were characterized by an increase in the amplitude of alpha rhythm during the intersession period and by an increase in theta rhythm in the session period.

Auditory priming improves neural synchronization in auditory-motor entrainment

Neurophysiological research has shown that auditory and motor systems interact during movement to rhythmic auditory stimuli through a process called entrainment. This study explores the neural oscillations underlying auditory-motor entrainment using electroencephalography. Forty young adults were randomly assigned to one of two control conditions, an auditory-only condition or a motor-only condition, prior to a rhythmic auditory-motor synchronization condition (referred to as combined condition). Participants assigned to the auditory-only condition auditory-first group) listened to 400 trials of auditory stimuli presented every 800 ms, while those in the motor-only condition (motor-first group) were asked to tap rhythmically every 800 ms without any external stimuli. Following their control condition, all participants completed an auditory-motor combined condition that required tapping along with auditory stimuli every 800 ms. As expected, the neural processes for the combined condition for each group were different compared to their respective control condition. Time-frequency analysis of total power at an electrode site on the left central scalp (C3) indicated that the neural oscillations elicited by auditory stimuli, especially in the beta and gamma range, drove the auditory-motor entrainment. For the combined condition, the auditory-first group had significantly lower evoked power for a region of interest representing sensorimotor processing (4–20 Hz) and less total power in a region associated with anticipation and predictive timing (13–16 Hz) than the motor-first group. Thus, the auditory-only condition served as a priming facilitator of the neural processes in the combined condition, more so than the motor-only condition. Results suggest that even brief periods of rhythmic training of the auditory system leads to neural efficiency facilitating the motor system during the process of entrainment. These findings have implications for interventions using rhythmic auditory stimulation.

Large-scale functional networks connect differently for processing words and symbol strings.

Reconfigurations of synchronized large-scale networks are thought to be central neural mechanisms that support cognition and behavior in the human brain. Magnetoencephalography (MEG) recordings together with recent advances in network analysis now allow for sub-second snapshots of such networks. In the present study, we compared frequency-resolved functional connectivity patterns underlying reading of single words and visual recognition of symbol strings. Word reading emphasized coherence in a left-lateralized network with nodes in classical perisylvian language regions, whereas symbol processing recruited a bilateral network, including connections between frontal and parietal regions previously associated with spatial attention and visual working memory. Our results illustrate the flexible nature of functional networks, whereby processing of different form categories, written words vs. symbol strings, leads to the formation of large-scale functional networks that operate at distinct oscillatory frequencies and incorporate task-relevant regions. These results suggest that category-specific processing should be viewed not so much as a local process but as a distributed neural process implemented in signature networks. For words, increased coherence was detected particularly in the alpha (8–13 Hz) and high gamma (60–90 Hz) frequency bands, whereas increased coherence for symbol strings was observed in the high beta (21–29 Hz) and low gamma (30–45 Hz) frequency range. These findings attest to the role of coherence in specific frequency bands as a general mechanism for integrating stimulus-dependent information across brain regions.

S20. EEG features of nonconvulsive seizures in critically ill patients - Findings from the TRENdS trial

Introduction There is little data on the EEG features of seizures seen critically ill patients having nonconvulsive seizures (NCS). The Treatment of Recurrent Electrographic Nonconvulsive Seizures (TRENdS) study enrolled 74 such subjects and randomized them to treatment with lacosamide or fosphenytoin. This study evaluates the EEG features of a subset of these subjects. Methods EEG features of 36 of the 74 subjects enrolled in the TRENdS study were analyzed in detail. The extent of spread, onset frequency, offset frequency and morphology of the most common seizure type was assessed. Results In this cohort, the average number of seizures per subject was 35.9 (range 1–339). Seizures were limited to one quadrant (11, 30.6%) or hemispheric (11, 30.6%) in most subjects. Another 14 (38.8%) subjects had seizures that were generalized, bilateral but not generalized or spread to varying extent. Most subjects had seizures with delta frequency onset (18, 50%), while another 9 (25%) had theta frequencies at onset. Another 9 (25%) subjects had seizure onset frequencies in alpha or beta range, or had seizures with varying onset frequencies. At seizure termination, delta frequencies were noted in 29 (80.6%) subjects, while 7 (19.4%) had various other frequencies. The morphology of the seizures was a rhythmic discharge in 17 (47.2%) subjects, recurrent spike or sharp discharges in 5 (13.9%), recurrent spike and wave discharges in 5 (13.9%) and various other morphologies in 9 (25%) others. Conclusion NCS in this cohort of subjects were mostly limited to one hemisphere. The seizure onset frequencies were most often in the delta and theta range, while delta frequencies were noted most often at offset. Rhythmic discharges were the most common morphology.

S67. Corticomuscular coherence in childhood dystonia

There is growing evidence of abnormal sensorimotor processing in idiopathic and genetic dystonias.Mechanisms may differ in patients with secondary/acquired dystonias, but there are few physiological studies in this group.Corticomuscular coherence (CMC) quantifies synchrony between oscillatory EEG and EMG activity and reflects bidirectional cortex-muscle interaction.Beta range CMC is modulated by sensory stimuli..Several studies show elevated 3–7 Hz intermuscular coherence (IMC) in myoclonus dystonia or DYT1 dystonia.Neither IMC or CMC have been studied in acquired dystonia.This study aimed to record CMC/IMC in children with genetic/idiopathic and acquired dystonia, and to assess its modulation by afferent stimuli. 16 children with dystonia and 13 typically developing children (TDC) participated (age 12–18 yrs).The child grasped a 15 cm ruler between thumb and index finger of the dominant hand.Mechanical perturbations to the ruler were provided by an electromechanical tapper.Surface EMG was recorded from First dorsal interosseous (FDI) and forearm extensors (FEx).Bipolar scalp EEG was recorded over contralateral sensorimotor cortex.Up to 200 5-s epochs of data were collected per subject.EMG and EEG signals were amplified, bandpass filtered (EEG 0.5–100 Hz; EMG 5–250 Hz) and sampled at 1024 Hz.Coherence was calculated for EEG:FDI, EEG:FEx and FDI:FEx using a short-time Fourier transform giving a frequency resolution of 2 Hz.95% confidence levels for significant coherence were calculated for each child.Bonferroni correction was applied to maintain type I error level at 0.05.The 500 ms window was moved across the 5-s data epoch in 50 ms steps to assess CMC/IMC change over time.CMC/IMC was compared between baseline, early (0.5–2 s) and late (2.0–3.5 s) post-stimulus periods using Fisher transformed coherency and Student t-test.Findings were compared between groups. Significant beta range (14–36 Hz) CMC and IMC was detected post-stimulus in all children, but was seen more consistently in the TDCs.An adult pattern of beta CMC/IMC modulation (McCelland et al., 2012) was seen in 10/13 TDCs versus only 4/16 children with dystonia (all acquired).For the TDC group, beta-CMC for combined FDI:EEG and FEx:EEG increased significantly from baseline to the early post-stimulus period (p = 0.015), returning to baseline in the late post-stimulus period.For the genetic and acquired dystonia groups the beta-CMC in the post-stimulus period was not significantly increased from baseline.For IMC, the change from baseline to early post-stimulus was significant for both the TDC (p = 0.003), and the acquired dystonia group (p = 0.047) but not the genetic/idiopathic dystonia group(p = 0.088). Beta range CMC can be identified in children with dystonia but both its magnitude and its modulation by sensory stimulation are less consistent than in TDCs. The findings also suggest differences in CMC/IMC between genetic/idiopathic vs acquired dystonia.

Improved cognitive morning performance in healthy older adults following blue-enriched light exposure on the previous evening

ObjectivesExposure to light can have acute alerting and circadian phase-shifting effects. This study investigated the effects of evening exposure to blue-enriched polychromatic white (BEL) vs. polychromatic white light (WL) on sleep inertia dissipation the following morning in older adults. MethodsTen healthy older adults (average age = 63.3 yrs; 6F) participated in a 13-day study comprising three baseline days, an initial circadian phase assessment, four days with 2-h evening light exposures, a post light exposure circadian phase assessment and three recovery days. Participants were randomized to either BEL or WL of the same irradiance for the four evening light exposures. On the next mornings at 2, 12, 22 and 32 min after each wake time, the participants completed a 90-s digit-symbol substitution test (DSST) to assess working memory, and objective alertness was assessed using a wake EEG recording. DSST and power density from the wake EEG recordings were compared between the two groups. ResultsDSST performance improved with time awake (p < 0.0001) and across study days in both light exposure groups (p < 0.0001). There was no main effect of group, although we observed a significant day x group interaction (p = 0.0004), whereby participants exposed to BEL performed significantly better on the first two mornings after light exposures than participants in WL (post-hoc, p < 0.05). On those days, the BEL group showed higher EEG activity in some of the frequency bins in the sigma and beta range (p < 0.05) on the wake EEG. ConclusionExposure to blue-enriched white light in the evening significantly improved DSST performance the following morning when compared to polychromatic white light. This was associated with a higher level of objective alertness on the wake EEG, but not with changes in sleep or circadian timing.

Transgenerational effects of the genocide against the Tutsi in Rwanda: A post-traumatic stress disorder symptom domain analysis

Background: A number of studies have investigated transgenerational effects of parental post-traumatic stress disorder (PTSD) and its repercussions for offspring. Few studies however, have looked at this issue in the African context. Methods: The present study addresses this gap, utilizing confirmatory factor analysis (CFA), to investigate symptom severity within the three Diagnostic and Statistical Manual of Mental Disorders IV (DSM-IV) PTSD symptom domains in mothers exposed to the genocide against the Tutsi in Rwanda (n=25) and offspring (n=25), and an ethnically matched control group of mothers (n=25) and offspring (n=25) who were outside of Rwanda during the genocide. All mothers were pregnant during the time of the genocide with the offspring included in the study. Missing data were excluded from the analyses. Results: We found that among the three symptom domains of PTSD, the re-experiencing symptom domain loaded most strongly onto PTSD among mothers directly exposed to the genocide (Beta = 0.95). In offspring of exposed mothers, however, the three symptom domains of PTSD yielded almost equal loading values (Beta range = 0.84-0.86). Conversely, among non-exposed mothers and their offspring, the hyperarousal symptom domain of PTSD loaded most strongly onto PTSD (Beta = 1.00, Beta = 0.94, respectively). As a secondary analysis, we also explored the relation between DNA methylation in the glucocorticoid receptor (NR3C1) locus, an important stress modulating gene, and individual PTSD symptom domains, finding a strong association between DNA methylation and re-experiencing among genocide-exposed mothers that exceeded any other observed associations by approximately two-fold. Conclusions: This is the first report, to our knowledge, of a symptom-based analysis of transgenerational transmission of PTSD in Africa. These findings can be leveraged to inform further mechanistic and treatment research for PTSD.

Reference Data for Polysomnography-Measured and Subjective Sleep in Healthy Adults.

Reference data for sleep are needed for the interpretation of clinical sleep parameters. This analysis aimed to provide polysomnography-measured, spectral analytic and subjective reference data based on a sample of healthy adults. In addition, effects of age and sex were investigated. The sample was selected from the archival database of the Sleep Center at the University Medical Center Freiburg and consisted of 206 healthy adults aged 19 to 73 years. For an adaptation and a second examination night, polysomnography parameters, spectral analytic data, and subjective sleep estimations are presented. With increasing age, sleep became shorter (less total sleep time, more wake time after sleep onset) and lighter (eg, more percentage of stage N1 sleep, increase in fast activity in the beta range). Sleep in females was deeper than sleep in males (eg, higher percentage of stage N3 sleep). Females had higher overall power density than males. Altogether, it is apparent that sleep parameters exhibit high standard deviations, suggesting a high variability within healthy adults and complicating the specification of reference values. Our data suggest that the informative value of sleep reference data in healthy individuals is limited because of high interindividual and intraindividual variation within sleep variables. More research, preferably in the form of meta-analyses and/or large international databases, is needed to further investigate the relevance of such reference data for mental and physical health. In the absence of such knowledge, giving patients feedback about deviations from the norm in their sleep profile may give rise to ill-founded concerns and worry.

Time estimation and beta segregation: An EEG study and graph theoretical approach.

Elucidation of the neural correlates of time perception constitutes an important research topic in cognitive neuroscience. The focus to date has been on durations in the millisecond to seconds range, but here we used electroencephalography (EEG) to examine brain functional connectivity during much longer durations (i.e., 15 min). For this purpose, we conducted an initial exploratory experiment followed by a confirmatory experiment. Our results showed that those participants who overestimated time exhibited lower activity of beta (18–30 Hz) at several electrode sites. Furthermore, graph theoretical analysis indicated significant differences in the beta range (15–30 Hz) between those that overestimated and underestimated time. Participants who underestimated time showed higher clustering coefficient compared to those that overestimated time. We discuss our results in terms of two aspects. FFT results, as a linear approach, are discussed within localized/dedicated models (i.e., scalar timing model). Second, non-localized properties of psychological interval timing (as emphasized by intrinsic models) are addressed and discussed based on results derived from graph theory. Results suggested that although beta amplitude in central regions (related to activity of BG-thalamocortical pathway as a dedicated module) is important in relation to timing mechanisms, the properties of functional activity of brain networks; such as the segregation of beta network, are also crucial for time perception. These results may suggest subjective time may be created by vector units instead of scalar ticks.

Improving neurophysiological biomarkers for functional myoclonic movements

IntroductionDifferentiating between functional jerks (FJ) and organic myoclonus can be challenging. At present, the only advanced diagnostic biomarker to support FJ is the Bereitschaftspotential (BP). However, its sensitivity is limited and its evaluation subjective. Recently, event related desynchronisation in the broad beta range (13–45 Hz) prior to functional generalised axial (propriospinal) myoclonus was reported as a possible complementary diagnostic marker for FJ. Here we study the value of ERD together with a quantified BP in clinical practice. MethodsTwenty-nine patients with FJ and 16 patients with cortical myoclonus (CM) were included. Jerk-locked back-averaging for determination of the ‘classical’ and quantified BP, and time-frequency decomposition for the event related desynchronisation (ERD) were performed. Diagnostic gain, sensitivity and specificity were obtained for individual and combined techniques. ResultsWe detected a classical BP in 14/29, a quantitative BP in 15/29 and an ERD in 18/29 patients. At group level we demonstrate that ERD in the broad beta band preceding a jerk has significantly higher amplitude in FJ compared to CM (respectively −0.14 ± 0.13 and +0.04 ± 0.09 (p < 0.001)). Adding ERD to the classical BP achieved an additional diagnostic gain of 53%. Furthermore, when combining ERD with quantified and classical BP, an additional diagnostic gain of 71% was achieved without loss of specificity. ConclusionBased on the current findings we propose to the use of combined beta ERD assessment and quantitative BP analyses in patients with a clinical suspicion for all types of FJ with a negative classical BP.

O-3-5. Beta oscillation in the thalamic Vim single unit activities is not predominant in upper limb dystonia

Thalamic Vim is a relay nucleus from the cerebellum and one of the targets for relieving symptoms of upper limb dystonia as well as tremor-dominant Parkinson’s disease (PD) and essential tremor (ET). Beta oscillation is reported to be predominant from the single unit analysis in this nucleus in PD, ET and chronic pain (Basha D et al., 2014). We analyzed the Vim oscillation at rest in five cases with upper limb dystonia (four females, mean age of 31.2 yo) to elucidate whether beta oscillation is predominant also in dystonia. Single unit activities were recorded with microelectrodes during stereotactic surgery while the patients were awake. Each single unit was identified(?) with template matching method at sites where ablation or deep brain stimulation were effective. In results, the spike frequency in the beta range was not predominant (beta: 14–30 Hz 29 ± 7% (SD), below theta: 3–7 Hz 31 ± 13%, alpha: 8–13 Hz 20 ± 10%, gamma: above 31 Hz 20 ± 18%, n = 33). In dystonia, oscillation pattern at rest in Vim is abnormal in Vim but beta oscillation is not predominant, demonstrating a distinctive pattern from those in PD, ET, and chronic pain.

Cholinergic Modulation of Frontoparietal Cortical Network Dynamics Supporting Supramodal Attention.

A critical function of attention is to support a state of readiness to enhance stimulus detection, independent of stimulus modality. The nucleus basalis magnocellularis (NBM) is the major source of the neurochemical acetylcholine (ACh) for frontoparietal cortical networks thought to support attention. We examined a potential supramodal role of ACh in a frontoparietal cortical attentional network supporting target detection. We recorded local field potentials (LFPs) in the prelimbic frontal cortex (PFC) and the posterior parietal cortex (PPC) to assess whether ACh contributed to a state of readiness to alert rats to an impending presentation of visual or olfactory targets in one of five locations. Twenty male Long-Evans rats underwent training and then lesions of the NBM using the selective cholinergic immunotoxin 192 IgG-saporin (0.3 μg/μl; ACh-NBM-lesion) to reduce cholinergic afferentation of the cortical mantle. Postsurgery, ACh-NBM-lesioned rats had less correct responses and more omissions than sham-lesioned rats, which changed parametrically as we increased the attentional demands of the task with decreased target duration. This parametric deficit was found equally for both sensory targets. Accurate detection of visual and olfactory targets was associated specifically with increased LFP coherence, in the beta range, between the PFC and PPC, and with increased beta power in the PPC before the target's appearance in sham-lesioned rats. Readiness-associated changes in brain activity and visual and olfactory target detection were attenuated in the ACh-NBM-lesioned group. Accordingly, ACh may support supramodal attention via modulating activity in a frontoparietal cortical network, orchestrating a state of readiness to enhance target detection.SIGNIFICANCE STATEMENT We examined whether the neurochemical acetylcholine (ACh) contributes to a state of readiness for target detection, by engaging frontoparietal cortical attentional networks independent of modality. We show that ACh supported alerting attention to an impending presentation of either visual or olfactory targets. Using local field potentials, enhanced stimulus detection was associated with an anticipatory increase in power in the beta oscillation range before the target's appearance within the posterior parietal cortex (PPC) as well as increased synchrony, also in beta, between the prefrontal cortex and PPC. These readiness-associated changes in brain activity and behavior were attenuated in rats with reduced cortical ACh. Thus, ACh may act, in a supramodal manner, to prepare frontoparietal cortical attentional networks for target detection.

Frequency modulation of neural oscillations according to visual task demands

Temporal integration in visual perception is thought to occur within cycles of occipital alpha-band (8-12 Hz) oscillations. Successive stimuli may be integrated when they fall within the same alpha cycle and segregated for different alpha cycles. Consequently, the speed of alpha oscillations correlates with the temporal resolution of perception, such that lower alpha frequencies provide longer time windows for perceptual integration and higher alpha frequencies correspond to faster sampling and segregation. Can the brain's rhythmic activity be dynamically controlled to adjust its processing speed according to different visual task demands? We recorded magnetoencephalography (MEG) while participants switched between task instructions for temporal integration and segregation, holding stimuli and task difficulty constant. We found that the peak frequency of alpha oscillations decreased when visual task demands required temporal integration compared with segregation. Alpha frequency was strategically modulated immediately before and during stimulus processing, suggesting a preparatory top-down source of modulation. Its neural generators were located in occipital and inferotemporal cortex. The frequency modulation was specific to alpha oscillations and did not occur in the delta (1-3 Hz), theta (3-7 Hz), beta (15-30 Hz), or gamma (30-50 Hz) frequency range. These results show that alpha frequency is under top-down control to increase or decrease the temporal resolution of visual perception.

Spatio-temporal dynamics of cortical drive to human subthalamic nucleus neurons in Parkinson's disease

Pathological synchronisation of beta frequency (12–35Hz) oscillations between the subthalamic nucleus (STN) and cerebral cortex is thought to contribute to motor impairment in Parkinson's disease (PD). For this cortico-subthalamic oscillatory drive to be mechanistically important, it must influence the firing of STN neurons and, consequently, their downstream targets. Here, we examined the dynamics of synchronisation between STN LFPs and units with multiple cortical areas, measured using frontal ECoG, midline EEG and lateral EEG, during rest and movement. STN neurons lagged cortical signals recorded over midline (over premotor cortices) and frontal (over prefrontal cortices) with stable time delays, consistent with strong corticosubthalamic drive, and many neurons maintained these dynamics during movement. In contrast, most STN neurons desynchronised from lateral EEG signals (over primary motor cortices) during movement and those that did not had altered phase relations to the cortical signals. The strength of synchronisation between STN units and midline EEG in the high beta range (25–35Hz) correlated positively with the severity of akinetic-rigid motor symptoms across patients. Together, these results suggest that sustained synchronisation of STN neurons to premotor-cortical beta oscillations play an important role in disrupting the normal coding of movement in PD.

Ion‐Scale Spectral Break in the Normal Plasma Beta Range in the Solar Wind Turbulence

AbstractThe spectral break (fb) of magnetic fluctuations at the ion scale in the solar wind is considered to give important clue on the turbulence dissipation mechanism. Among several possible mechanisms, the most notable two are related respectively to proton thermal gyroradius ρi and proton inertial length di. The corresponding frequencies of them are fρi=VSW/(2πρi) and fdi=VSW/(2πdi), respectively, where VSW is the solar wind speed. However, no definite conclusion has been given for which one is more reasonable because the two parameters have similar value when plasma beta β ∼ 1. Here we do a statistical study to see if the two ratios fb/fρi and fb/fdi have different dependence on β in the solar wind turbulence with 0.1 &lt; β &lt; 1.3. From magnetic measurements by the Wind spacecraft, we select 141 data sets with each one longer than 13 h. We find that the ratio fb/fdi is statistically not dependent on β, and the average value of it is 0.48 ± 0.06. However, fb/fρi increases with increasing β clearly and is significantly smaller than fb/fdi when β &lt; 0.8. These new results show that fb is statistically 0.48fdi, and the influence of β could be negligible in the studied β range. It indicates a preference of the dissipation mechanism associated with di in the solar wind with 0.1 &lt; β &lt; 0.8. Further theoretical studies are needed to give detailed explanation.

Climate change as a driver of biotic homogenization of woody plants in the Atlantic Forest

AbstractAimThe importance of anthropogenic activities in reshaping biodiversity is increasing fast. Interactive effects of climate change, biological invasions and species replacement are poorly understood, particularly at large scales and in megadiverse biomes. We aimed to assess the effects of climate change as a driver of spatio‐temporal biodiversity patterns and homogenization of woody plants at multiple scales, in a hyperdiverse species assemblage.LocationThe Atlantic Forest, Brazil.Time periodPresent, future projections.Major taxa studiedWoody plants.MethodsWe used ecological niche modeling to estimate geographic distributions of 2,255 plant species under present and future climates. Range‐diversity plots based on species presence‐absence matrices and null models were used to explore changes in alpha and beta diversity, range size and covariance in species composition across ecoregions, climatic scenarios and within protected areas. We also partitioned dissimilarity into turnover and nestedness components and explored expansions and retractions of species’ ranges to infer invasive potential and implications for conservation in the future.ResultsDespite a general increase in local richness, beta diversity decreased with time. Similarity among sites was accentuated in severe climate change scenarios enhancing biotic homogenization at large scales. Changes were not constant or homogeneous across ecoregions and at smaller scales, but a consistent pattern was the reduction of beta diversity accompanied by increments in the mean range size of widespread species. Likewise, subsets of assemblages within protected areas presented higher similarity, increased mean range size and invariability of richness through time, indicating potential compositional turnover promoted by the expansion of widespread species.Main conclusionsExpansion of current generalist and disturbance‐tolerant species rather than extinction or retraction of local endemics may lead to woody plant homogenization in the tropics. The woody plant assemblage in the Atlantic Forest is prone to a structural reorganization due to climate change, threatening conservation of biodiversity and potentially leading to severe large‐scale biotic homogenization in the near future.

EEG frequency PCA in EEG-ERP dynamics.

Principal components analysis (PCA) has long been used to decompose the ERP into components, and these mathematical entities are increasingly accepted as meaningful and useful representatives of the electrophysiological components constituting the ERP. A similar expansion appears to be beginning in regard to decomposition of the EEG amplitude spectrum into frequency components via frequency PCA. However, to date, there has been no exploration of the brain's dynamic EEG-ERP linkages using PCA decomposition to assess components in each measure. Here, we recorded intrinsic EEG in both eyes-closed and eyes-open resting conditions, followed by an equiprobable go/no-go task. Frequency PCA of the EEG, including the nontask resting and within-task prestimulus periods, found seven frequency components within the delta to beta range. These differentially predicted PCA-derived go and no-go N1 and P3 ERP components. This demonstration suggests that it may be beneficial in future brain dynamics studies to implement PCA for the derivation of data-driven components from both the ERP and EEG.

Brainstem Influence on Thalamocortical Oscillations during Anesthesia Emergence.

Theories of mechanisms that impair or prevent consciousness during anesthesia that are related to thalamocortical oscillations have been proposed. Many methods of EEG analysis have been proposed as measures of anesthetic effects but only a few have potential to provide measures of those anesthetic effects that are directly related to thalamocortical oscillations. Some of these methods will be explained and demonstrated with examples chosen to provide evidence for or against two of the proposed mechanisms. The first of the two mechanisms to be addressed is the “traveling peak” (Ching et al., 2010), which relates to anesthetic agents synchronizing neural oscillations that occur in subjects who are awake and reducing their frequency from the gamma (25–40 Hz) to the beta range (13–24 Hz) as a state of sedation develops. The mechanism continues to lower the frequency of this oscillation to the alpha (8–12 Hz) range. In the alpha frequency range, responses to sounds and words stop. It has been proposed that the mechanism changes fundamentally at this point and the oscillations are not compatible with consciousness. The second mechanism that will be addressed is a modification of the generally accepted mechanism for the spindle oscillations that occur during natural sleep (Steriade et al., 1993a,b). These two different mechanisms imply two different patterns for changes in the frequency of the thalamocortical oscillations during emergence. The first mechanism implies that the frequency of the oscillations should increase from the alpha range to the beta range during emergence. The “spindle” mechanism implies that the frequency of the oscillation would not increase much beyond the alpha range. Examples of EEG recordings during anesthesia and emergence from anesthesia were found which were consistent with either mechanism alone or both mechanisms at the same time. Neither theory was able to explain all examples. It is possible that both mechanisms can occur and that brainstem activity may influence the characteristics of emergence. The brainstem activity in question may be influenced by nociception and analgesic supplementation. It may be possible to control the path of emergence by controlling brainstem activity with opioids and other agents in order to allow the patient to awaken without going through an excitement phase or delirium at the transition to consciousness.

PB 20 Anodal tDCS over the left sensorimotor area improves motor function and suppresses cortical beta activity in Parkinson’s disease

Motor network activity in the beta range is correlated with motor symptoms in Parkinson’s disease (PD). Anodal tDCS over the sensorimotor area modulates cortical excitability and may alleviate motor symptoms in PD. In this study, we aimed to explore the effect of anodal transcranial direct current stimulation over the left sensorimotor area on clinical motor outcome, right hand fine motor performance and cortical motor network activity. In this double-blind randomized sham-controlled combined EEG and tDCS study, we investigated ten pharmacologically treated idiopathic PD patients after overnight withdrawal of dopaminergic medication and eleven healthy controls during an isometric precision grip task before and after stimulation. Participants were studied and crossed-over in two sessions on different days with either “verum” or “sham” stimulation of anodal tDCS (20 min; 1 mA; electrodes placed over left ‘C3’ (anode) and right ‘Fp2’ (cathode)). Cortical activity was expressed as frequency domain spectrum (power) and the topographic distribution was obtained from 25 cortical EEG channels placed according to the 10–20 system. Fine motor performance was expressed as accuracy error during the precision grip task with lower accuracy error indicating higher motor precision. Clinical motor outcome was measured using the UPDRS III motor score. PD patients with “verum” stimulation showed a significant decrease of beta power over the left primary motor area (electrode position ‘C3’) centered from 22 to 27 Hz and a significant decrease in the UPDRS III motor score. Both changes were most pronounced directly after stimulation and lasted for at least 30 min. These effects were specific for the PD “verum” condition and absent in both PD “sham” and in healthy controls “verum” and “sham” conditions. Both groups showed no significant change regarding the accuracy error after stimulation. Anodal tDCS applied to the left sensorimotor area induces beta power decrease over the left primary motor area and clinical motor improvement in PD.