Human gamma oscillations during slow wave sleep

Neocortical local field potentials have shown that gamma oscillations occur spontaneously during slow-wave sleep (SWS). At the macroscopic EEG level in the human brain, no evidences were reported so far. In this study, by using simultaneous scalp and intracranial EEG recordings in 20 epileptic subjects, we examined gamma oscillations in cerebral cortex during SWS. We report that gamma oscillations in low (30-50 Hz) and high (60-120 Hz) frequency bands recurrently emerged in all investigated regions and their amplitudes coincided with specific phases of the cortical slow wave. In most of the cases, multiple oscillatory bursts in different frequency bands from 30 to 120 Hz were correlated with positive peaks of scalp slow waves ("IN-phase" pattern), confirming previous animal findings. In addition, we report another gamma pattern that appears preferentially during the negative phase of the slow wave ("ANTI-phase" pattern). This new pattern presented dominant peaks in the high gamma range and was preferentially expressed in the temporal cortex. Finally, we found that the spatial coherence between cortical sites exhibiting gamma activities was local and fell off quickly when computed between distant sites. Overall, these results provide the first human evidences that gamma oscillations can be observed in macroscopic EEG recordings during sleep. They support the concept that these high-frequency activities might be associated with phasic increases of neural activity during slow oscillations. Such patterned activity in the sleeping brain could play a role in off-line processing of cortical networks.     

与突触可塑性相关的神经振荡和信息流研究

作为一种有节律的神经活动,神经振荡现象发生在所有的神经系统中,例如大脑皮层、海马、皮层下神经核团以及感觉器官.本综述首先给出了已有的研究结果,即基于theta和gamma频段的同步神经振荡揭示了认知过程的起源与本质,如学习与记忆.然后介绍了关于神经振荡分析的新技术和算法,如表征神经元突触可塑性的神经信息流方向指数,并例...     

Substrate-dependent control of ERK phosphorylation can lead to oscillations

The extracellular signal-regulated kinase (ERK) controls cellular processes by phosphorylating multiple substrates. The ERK protein can use the same domains to interact with phosphatases, which dephosphorylate and deactivate ERK, and with substrates, which connect ERK to its downstream effects. As a consequence, substrates can compete with phosphatases and control the level of ERK phosphorylation. We propose that this effect can qualitatively change the dynamics of a network that controls ERK activation. On its own, this network can be bistable, but in a larger system, where ERK accelerates the degradation of a substrate competing with a phosphatase, this network can oscillate. Previous studies proposed that oscillatory ERK signaling requires a negative feedback in which active ERK reduces the rate at which it is phosphorylated by upstream kinase. We argue that oscillations can also emerge even when this rate is constant, due to substrate-dependent control of ERK phosphorylation.     

Renal SNA as the primary mediator of slow oscillations in blood pressure during hemorrhage

Blood pressure contains a distinct low-frequency oscillation often termed the Mayer wave. This oscillation is caused by the action of the sympathetic nervous system on the vasculature and results from time delays in the baroreflex feedback loop for the control of sympathetic nerve activity (SNA) in response to changes in blood pressure. In this study, we used bilateral renal denervation to test the hypothesis that it is SNA to the kidney that contributes a large portion of the vascular resistance associated with changes in the strength of the slow oscillation in blood pressure. In conscious rabbits, SNA and blood pressure were measured during hemorrhage (blood withdrawal at 1.35 ml. min(-1). kg(-1) for 20 min). Spectral analysis identified a strong increase in power at 0.3 Hz in SNA and blood pressure in the initial compensatory phase of hemorrhage before blood pressure started to fall. However, in a separate group of renal denervated rabbits, although the power of the 0.3-Hz oscillation under control conditions in blood pressure was similar, it was not altered during hemorrhage. Wavelet analysis revealed the development of low-frequency oscillations at 0.1 Hz in both intact and denervated animals. In conclusion, we propose that changes in the strength of the oscillation at 0.3 Hz in arterial pressure during hemorrhage are primarily mediated by sympathetic activity directed to the kidney.     

光流信息加工的神经基础

自体运动时,分布在视野内的景物在视网膜上的像旋转,扩张／收缩,浃动,构成光流刺激,光流信息的检测对于人或动物确定前进的方向,速度至关重要,已成为运动信息加工的一个研究热点。本文概括介绍了近年来心理物理和生理学两方面有关光流信息加工研究的主要进展,并讨论了光流信息分析的神经机制。     

Preferential axial flow during high-frequency oscillations: effects of gas density

Allen et al. (J. Clin. Invest. 76: 620-629, 1985) reported that regional phasic lung distension during high-frequency oscillations (HFO) is substantially and systemically heterogeneous when both frequency (f) and tidal volume (VT) are large. They hypothesized that this phenomenon was attributable to central airway geometry and preferential axial flow induced therein by the momentum flux of the inspiratory gas stream. According to that hypothesis, the observed distribution of phasic lung distension would depend on the ratio VT/VD* (where VD* is an index of anatomic dead space), independent of gas density (rho), when f is scaled in proportion to lung resonant frequency, fo. To test this hypothesis, we used the methods of Allen et al. (ibid.) to study six excised dog lungs during HFO (f = 2-32 Hz; VT = 5-80 ml) using gases of different densities. Alveolar pressure excursions (PA) were measured as rho spanned a 12-fold range using He, air, and SF6. The apex-to-base and right-to-left ratios of PA were used as indexes of regional heterogeneity of phasic lung distension. For each gas at low f, distension of the lung base was favored slightly independent of VT, but at higher f distension of the lung apex was favored when VT was small, whereas distension of the lung base was favored when VT was large. In addition, we observed substantial right-to-left differences in apical lobes during oscillation at high f not seen before.(ABSTRACT TRUNCATED AT 250 WORDS)     

加工假基因演化过程中的两种信息流

定义描述DNA序列组分差异性和碱基关联的两个参数,分析了人类加工假基因演化过程中其组分信息和碱基关联信息的变化特征,发现随时间的推移,加工假基因的组分逐步向其侧翼序列漂移,紧邻碱基关联逐步增强。这表明本研究所得参数可很好地用来表征加工假基因的突变信息。     

Osteoblastic cells have refractory periods for fluid-flow-induced intracellular calcium oscillations for short bouts of flow and display multiple low-magnitude oscillations during long-term flow

Partitioning a daily mechanical stimulus into discrete loading bouts enhances bone formation in rat tibiae (J. Bone Mineral Res. 15(8) (2000) 1596). We hypothesized that a refractory period exists in primary rat osteoblastic cells, during which fluid-flow-induced [Ca(2+)](i) oscillations are insensitive to additional short bouts (2 min) of fluid flow. Because the frequency of [Ca(2+)](i) oscillations is believed to be important for regulating cellular activity and long-term fluid flow alters gene expression in bone cells, we also hypothesized that long-term (15 min) oscillating fluid flow produces multiple [Ca(2+)](i) oscillations in osteoblastic cells. Primary osteoblastic cells from rat long bones were exposed to 2 min of oscillating fluid flow that produced shear stresses of 2 Pa at 2 Hz. After a rest period of 5, 30, 60, 300, 600, 900, 1800, or 2700 s, the cells were exposed to a second 2-min bout of flow. A 600 s rest period was required to recover the percentage of cells responding to fluid flow and a 900 s rest period was required to recover the [Ca(2+)](i) oscillation magnitude. The magnitude and shape of the two [Ca(2+)](i) oscillations were strikingly similar for individual cells after a 900 s rest period. During 15 min of continuous oscillating flow, some individual cells displayed between 1 and 9 oscillations subsequent to the initial [Ca(2+)](i) oscillation. However, only 54% of the cells that responded initially displayed subsequent [Ca(2+)](i) oscillations during long-term flow and the magnitude of the subsequent oscillations was only 28% of the initial response.     

Reversal of slow flow phenomenon during primary stenting by bail-out administration of abciximab

BACKGROUND: Slow flow or no reflow phenomenon is increasingly being recognized as a serious problem during coronary angioplasty and stenting. This phenomenon is seen more often during angioplasty in highly thrombogenic milieux, especially in a setting of acute myocardial infarction. The treatment of this complication is often not satisfactory. In this study the authors assessed the efficacy of abciximab, a potent antiplatelet drug, in treating slow flow or no reflow phenomenon during primary percutaneous transluminal coronary angioplasty (PTCA) for acute myocardial infarction (AMI). METHODS: Twenty-one instances of persistent slow flow phenomenon were encountered in 131 consecutive patients subjected to primary PTCA for AMI (16%). It was more common in patients presenting with AMI complicated by cardiogenic shock (nine of 21, 43%). Of these 21 cases of slow flow, 10 patients were given injection abciximab during the procedure of primary PTCA as a bail-out measure after encountering the complication of slow flow or no reflow. A pre-discharge coronary angiography was carried out in all patients who survived. RESULTS: In seven of 10 patients in the abciximab group flow had improved to TIMI-3. In contrast, in the non-abciximab group TIMI flow improved in only four of 11 patients. Patients with persistent slow flow had significantly higher mortality at the first 30-day follow-up than patients with TIMI-3 flow (33% versus 1.8%, p<0.001). CONCLUSION: In this small nonrandomized study significant improvement in coronary flow was achieved by using intravenous abciximab after observing slow flow or no reflow phenomenon during primary PTCA. More frequent use of this drug in this milieu might help in preventing the development of this complication. Larger studies are warranted to confirm this life-saving beneficial effect of bail-out administration of abciximab during primary angioplasty.     

Leg blood flow during slow head-down tilt with and without leg venous congestion

The effects of slow changes in body position on leg blood flow (LBF) were studied in nine healthy male subjects. Using a tilt table, sitting volunteers were tilted about 60° backwards to a supine position within 40 s. To modify the venous filling in the legs, the tilt manoeuvre was repeated with congestion of the leg veins induced by two thigh cuffs inflated to a subdiastolic pressure of 60 mmHg. Doppler measurements in the femoral artery were used to estimate LBF. Additional Doppler measurements at the aortic root in five of the subjects were taken for the determination of cardiac output. The LBF was influenced by body position. In the control experiment it increased from 500 ml · min⁻¹ in the upright to 780 ml · min^–1 after 15 min in the supine position. A mean maximal value of 950 ml · min⁻¹ was observed 20 s after the tilt. Heart rate remained almost constant during the tilt phase, whereas stroke volume increased from 90 ml to 120 ml and it remained at that level after the cessation of the tilt. Congestion of the leg veins had no significant effect on heart rate, stroke volume and mean blood pressure. However, it increased vascular resistance of the leg during and after the tilt. After 15 min in the tilted position LBF amounted to 600 ml · min⁻¹. The results suggest that the filling of the leg veins is inversely related to leg blood flow. The most likely mechanism underlying this observation is a local effect of venous filling on vasomotor tone. Accepted: 20 May 1998     

Investigating high-amplitude oscillations in rat tail skin blood flow during core heating and cooling

In a separate paper, we describe high-amplitude oscillations in human skin blood flow (Q˙_sk). Using an open-loop model in rats, we independently modulated and clamped hypothalamic and skin temperatures. Central heating reliably induced these high-amplitude oscillations in tail Q˙_sk, which occurred at 0.41±0.03 Hz spanning 758.1±25.7 ms, and were comprised of high-amplitude peaks (496.8±87.6 AU) arising from a stable baseline (114.1±27.6 AU). Central cooling significantly reduced Q˙_sk, but not the amplitude, the frequency, width or baseline of the oscillations. These observations indicate that such high-amplitude oscillations are not primarily mediated via central thermal state. Instead, we believe these oscillations to be turned on by an elevated skin temperature.     

Chelation of lead during co-exposure to ethanol

Efficacy of calcium disodium EDTA, D-penicillamine (DPA), 2,3 dimercaptosuccinic acid (DMSA), and alpha-mercapto-beta-(2-furyl) acrylic acid (MFA) to reduce the body burden of lead and restore the altered biochemical variables in lead or lead + ethanol administered rats was investigated. The investigation was aimed to suggest suitable prophylaxis of lead intoxication prevalent among workers co-exposed to lead and alcohol ingestion. Administration of lead (10 mg/kg, oral, once daily for 8 weeks) produced a significant inhibition in the activity of blood delta-aminolevulinic acid dehydratase (ALAD), elevation in the blood zinc protoporphyrin (ZPP) and urinary elimination of lead and delta-aminolevulinic acid (ALA). Lead contents of blood, liver, kidney and brain were also significantly higher than the normal control. The above changes were more marked in animals co-exposed to lead + ethanol (20% in drinking water) compared to lead alone. All the chelators were effective in increasing the urinary lead elimination, reducing the above biochemical alterations and lead contents of tissues. The order of effectiveness being DMSA greater than Calcium disodium EDTA greater than DPA greater than MFA. However, the protection was more noticeable in animals treated with lead alone than with lead and ethanol.     

Age-related differences in the dynamics of the skin blood flow oscillations during postocclusive reactive hyperemia

Age-related changes in peripheral microcirculation were studied using laser Doppler flowmetry in 60 apparently healthy subjects. The response of microcirculation to short-term ischemia was studied using the occlusion test. Changes in the amplitude of the peripheral blood flow oscillations were determined using time-amplitude analysis based on continuous adaptive wavelet filtration. The oscillation amplitude in the frequency range of the heart rate was found to reach the maximum with a delay after the removal of the occlusion, whereas in the range of the respiratory rhythm, no delay was observed. The hyperemic response to short-term ischemia is assumed to develop under the predominant influence of the arterial-arteriolar component, whereas the dynamics of amplitude oscillations in the range of the respiratory rhythm is a result of the devastation of the venular component after removal of occlusion. In response to short-term ischemia, the maximum oscillation amplitudes of myogenic, neurogenic, and endothelial rhythms decreased with age, which demonstrates the restriction of the regulatory control of the peripheral blood flow by the corresponding systems.     

Attention-induced deactivations in very low frequency EEG oscillations: differential localisation according to ADHD symptom status

Background

The default-mode network (DMN) is characterised by coherent very low frequency (VLF) brain oscillations. The cognitive significance of this VLF profile remains unclear, partly because of the temporally constrained nature of the blood oxygen-level dependent (BOLD) signal. Previously we have identified a VLF EEG network of scalp locations that shares many features of the DMN. Here we explore the intracranial sources of VLF EEG and examine their overlap with the DMN in adults with high and low ADHD ratings.

Methodology/Principal Findings

DC-EEG was recorded using an equidistant 66 channel electrode montage in 25 adult participants with high- and 25 participants with low-ratings of ADHD symptoms during a rest condition and an attention demanding Eriksen task. VLF EEG power was calculated in the VLF band (0.02 to 0.2 Hz) for the rest and task condition and compared for high and low ADHD participants. sLORETA was used to identify brain sources associated with the attention-induced deactivation of VLF EEG power, and to examine these sources in relation to ADHD symptoms. There was significant deactivation of VLF EEG power between the rest and task condition for the whole sample. Using s-LORETA the sources of this deactivation were localised to medial prefrontal regions, posterior cingulate cortex/precuneus and temporal regions. However, deactivation sources were different for high and low ADHD groups: In the low ADHD group attention-induced VLF EEG deactivation was most significant in medial prefrontal regions while for the high ADHD group this deactivation was predominantly localised to the temporal lobes.

Conclusions/Significance

Attention-induced VLF EEG deactivations have intracranial sources that appear to overlap with those of the DMN. Furthermore, these seem to be related to ADHD symptom status, with high ADHD adults failing to significantly deactivate medial prefrontal regions while at the same time showing significant attenuation of VLF EEG power in temporal lobes.     

儿童根据环境中的可靠信息来认路

本文考察3—4岁儿童在圆形空间中重新定位和找回玩具的能力。让儿童把玩具放到一个路标物体里。闭眼转圈后找回玩具,观察儿童寻找玩具的位置,并将它跟睁眼转圈后儿童寻找玩具的位置比较,从而考察儿童的认路能力。实验结果说明儿童不能利用路标物体所形成的几何结构和具有延展性信息的表面来认路,但可以根据环境中的可靠信息来认路,即路标物体的独特性信息。因此,我们认为儿童是根据环境中的可靠信息——路标物体的独特性来认路的。