模拟失重条件下与听觉方位区分关联的脑电位变化

目的探明模拟失重条件下听觉方位区分的脑反应特性 ,进一步了解模拟失重条件下脑功能的变化特点。方法 1 4名右利手正常被试者以头低位倾斜 ( - 1 0° ,HDT)模拟失重 ,头高位倾斜 ( + 1 0°,HUT)为对照。要求被试者对声音信号进行音调选择方位区分。结果靶和非靶信号均产生了明显的事件相关电位 (ERPs) ;与HUT相比 ,HDT条件下ERPs的变化表现为慢电位的负向偏移 ;ERPs的变化有一定的方位和脑区特征 ,即以右后方位的T ERPs受影响最大 ,右前方位受影响最小 ,且T和NT ERPs均以F5 区受影响最大。结论HDT对听觉方位区分时脑功能状态有一定的影响。     

视觉、前庭觉及其相互作用对视觉认知的动态影响

航天飞行初期,空间运动病、空间定向障碍一直是航天医学界的重要难题,而两者的发生机制均与视觉和前庭觉有着紧密的联系。如今视觉刺激、前庭刺激对脑高级认知功能影响的研究已展开,但视-前庭联合刺激下对脑高级认知功能影响的研究,还处于探索阶段。目前认知有关的研究手段有很多,其中具有毫秒级时间分辨率的脑事件相关电位(event-related potentials,ERPs)是一种较为客观且简便易行的研究方法。本文综述了视觉、前庭觉与脑高级功能联系的解剖学基础,介绍了采用ERP为研究手段的部分视觉认知研究动态以及视-前庭相互作用对脑高级功能影响的研究现状,提出了今后的研究方向,为今后开展该方面研究提供了参考。     

头低位模拟失重对听觉ERPs早成分的影响

目的观察头低位模拟失重对听觉事件关联电位 (ERPs)早成分的影响 ,进一步了解模拟失重条件下脑功能的变化特点。方法被试者为 1 4名右利手正常在校大学生 (2 0～ 2 3岁 )。以头低位倾斜 (- 1 0°,HDT)模拟失重 ,头高位倾斜 (+1 0°,HUT)为对照。要求被试者对 4个方位的声音信号进行音调选择方位区分反应 (SR)。在不同体位记录 4套SR作业的ERPs。对 -t和方差分析统计听觉ERPs早成分。结果与HUT相比 ,HDT条件下靶信号 (T)ERPs和非靶信号 (NT)ERPs早成分的平均幅值在第 4套作业时均显著降低 ,且以F5区受影响最大 ,并表现出一定的方位特征。结论HDT对听觉ERPs早成分有一定的抑制性影响 ,提示HDT下脑的警觉激活程度降低。     

WMN：非靶刺激加工过程中一个与工作记忆相关的视觉ERPs负成分

目的通过比较复杂程度不同的视觉作业中的非靶ERPs特征 ,探讨脑对非靶刺激的加工机制。方法 2 6名健康青年男性被试者 [( 2 1 .2± 3.3)岁 ]。刺激为等概率出现在左、右视场的红、绿闪光刺激 ,要求被试者对靶刺激 (红光或绿光 ,交叉规定 )进行拨开关 (SR)或方位区分 (DR) ,忽略非靶刺激。结果与SR相比 ,DR非靶ERPs在额区产生了 1 0 0～ 70 0ms的峰值在 380ms左右的负向慢波 -工作记忆负波(WMN ,workingmemorynegativity)。 结论ERPs负成分WMN的产生表明对非靶刺激除了感知加工过程 ,还可能涉及到对工作记忆中模式的消除和重新提取等脑活动过程 ,而这种脑活动主要发生在额区     

听觉空间方位区分作业中的两类脑慢电位反应

目的研究听觉方位区分ERPs的类型特征及其受模拟失重影响的差异。方法 1 4名右利手正常被试者。以头低位倾斜 ( - 1 0°,HDT)为模拟失重 ,头高位倾斜 ( + 1 0°,HUT)为对照。要求被试者对不同方位的声音信号进行音调选择方位区分 ,每种体位作 4套测试。记录 9导脑电。结果 1 )根据靶刺激ERPs的特点将被试者分成I类 (n =7)和II类 (n =7) ,其主要差异为II类被试者的ERPs出现显著的负慢电位 ( 1 5 0～ 75 0ms) ,行为指标亦表明II类被试者的错误率和反应时均高于I类 ,提示II类被试者的心理负荷比I类重 ;2 )II类ERPs受HDT条件影响的时间比I类更早 ,负向偏移更大 ,表明头低位模拟失重对II类ERPs的影响程度要大于I类。结论ERPs中的慢电位在一定程度上可以体现心理负荷和脑功能状态 ,在航天航空作业人员的选拔和训练中应注意听觉ERPs的特征及其承受心理负荷的状况。     

模拟失重对快慢反应被试视觉选择注意ERPs的不同影响

目的研究模拟失重对不同反应类型被试者脑功能影响的差异。方法14名右利手正常被试者。以头低位倾斜(-10°,HDT)为模拟失重,头高位倾斜( 20°,HUT)为对照。刺激为等概率出现在左、右视场的红、绿闪光刺激,要求被试者对靶刺激(红光或绿光,在被试者中交叉规定)进行方位区分反应(DR),忽略非靶刺激。每种体位2h,均作5套DR测试。记录9导脑电。结果1)根据反应时的长短将被试者分成快反应(n=7)和慢反应(n=7)两组,其事件相关电位(ERPs)的主要差异表现为快反应组的N1和P3的幅值更大、前脑区负向慢波NSW的潜伏期更短、幅值更大,提示快反应被试者的觉醒水平和注意程度较高、主动抑制能力较强,脑功能状态较好;2)HDT引起ERPs中P2和P3成分幅值的降低,慢反应组ERPs受HDT影响的程度比快反应组更显著。结论模拟失重对慢反应被试者ERPs的影响更严重,为航天脑功能的评价和航天员的选拔提供了一定的实验依据。     

脑功能区自动提取法的研究及在PET／CT功能显像中的应用

目的：验证脑功能区的自动提取法在18F-FDG PET/CT脑显像中提取位置的准确性,并初步探讨在视觉功能区和储尿功能区中的应用。方法：对14例正常人按有无光刺激分成二组进行18F-FDG PET/CT脑显像以及25例正常人储尿和未储尿状态下分别进行18F-FDG PET/CT脑显像,采用图像配准和图像形变方法,将脑图像标化到标准的Talairach坐标空间,按各脑部功能区对全脑中坐标点分类,分析光刺激和受储尿刺激影响的脑解剖功能核团。结果：该方法成功地将目标图像与标准坐标空间配准,提取的视觉脑功能区和储尿中枢位置符合解剖学定义。受光刺激,6个核团代谢增高,5个核团代谢降低。受储尿刺激13个核团代谢增高,9个核团代谢降低。结论：脑功能区自动提取法对PET/CT脑显像对特定脑区分析显示快速,准确,重现性好的特点,为研究特定脑感兴趣区提供了一个客观,细致分析方法。18F-FDG PET/CT脑显像为临床研究脑功能提供了功能-解剖学参考和重要的影像学方法。     

持续认知操作活动诱发脑疲劳状态时服用酪氨酸的效果观察

目的 观察持续认知操作活动期间服用酪氨酸（Tyr)的效果。为飞行2中使用提供依据。方法 8名健康男性青年在22：00-06：00期间持续完成大约8h的方知操作任务和有关量表评定,02：00和03：00接受Tyr（或安慰剂）试验,04：00和05：00完成脑事件相关电位（ERPs)的测量。次日完成与残留效应有关的脑功能状态评定及肝、肾功能检查。结果 Tyr明显缩短ERPs的P3潜伏期并减缓认知操作反应错误率的上升趋势,同时也减轻了嗜眠及脑疲劳症状,服用Tyr对肝、肾功能及次日的工作影响均不显著。结论 Tyr在对抗持续认知操作活动期间的能力下降及改善脑功能状态方面可能是一种相对无害的物质,存在应用于飞行员的可能性。     

等概率听觉选择反应中非靶ERPs的N2效应

目的研究等概率听觉选择反应任务中非靶ERPs的N2效应是否存在及其特点。方法被试者为1 6名右利手健康男性青年 ( 2 3 .2± 2 .1岁 )。刺激为听觉输入的一位数字信号序列 ( 2～ 7) ,要求被试者对靶数字进行拨开关反应 ,对非靶数字不作反应。记录 9导脑电。结果 1 )非靶ERPs产生了明显的N2 80 (N2效应 ) ,额区最为突出 ;2 )非靶ERPs中P3的潜伏期明显长于、峰值显著小于靶ERPs,且头皮分布比靶ERPs(顶区优势 )更趋于中央脑区分布。结论听觉通道亦存在非靶N2效应 ,且不能简单理解为是对靶刺激反应的抑制 ,而更可能反映了工作记忆中模式的重调过程 ,而这一过程的完成可能比靶数字出现时的反应更为复杂 ,且主要发生在额区     

基于水平集方法的图像分割

目的:提取T1加权MR脑图像中的侧脑室。方法:首先用高斯滤波对原始图像进行平滑,然后利用改进的FastMarching方法对脑图像进行分割。根据T1加权MR脑图像的成像特点并结合区域信息重新定义了Fast Marching方法的速度函数,该速度函数具有良好的抗泄漏能力。结果:对一系列T1加权MR脑图像进行了分割实验,成功提取出了侧脑室。结论:改善了传统Fast Marching方法在弱边界处易泄漏的缺陷,具有更好的分割效果。     

Time and frequency domain analysis of ground reaction forces during walking: an investigation of variability and symmetry

The purpose of this study was to investigate the variability and symmetry of ground reaction force (GRF) measurements during walking, using time and frequency domain analysis. Means and standard deviations of selected GRF time and frequency domain parameters for the left and right sides were calculated from 10 trials of each side. The results showed that a 10-trial mean GRF frequency content meets acceptable variability limits (<10%), and confirms the hypothesis of gait symmetry. The time domain variable results in the vertical and anterior-posterior directions agree with previous findings. In contrast, time domain parameters in the medial-lateral component are characterised by substantial asymmetries, probably due to the high variability found in this axis. Results indicated that overall pattern examination of the GRF curves using frequency analysis instead of isolated time domain parameters, is a more appropriate procedure for GRF comparisons.     

心率变异性与运动病关系的研究

目的　探讨心率变异性与运动病的关系。方法　根据出海实习学员运动病的发生情况 ,将学员分为运动病组和对照组各 2 0人 ,采集安静状态下的 5 2 0次窦性心搏 ,应用心率变异时域、频域分析方法评价自主神经功能状态。结果　运动病组时域指标 RR间期平均值的标准差 (SDNN)、相邻 RR间期差值的均方根 (r MSSD)、相邻 RR间期相差大于 5 0 m s占总心动周期数的百分比 (PNN50 )、HRV指数(HRVI)和频域指标低频 (L F)、高频 (HF)、总功率谱密度 (TP)均显著高于对照组 (P<0 .0 5 )。 RR间期平均值 (MRR)、极低频 (VL F)、低频与高频的比值 (L F/ HF)在两组间差异无显著性 (P>0 .0 5 )。结论　自主神经功能状态对运动病的发生存在明显的影响 ,迷走神经张力过高与运动病的发生有密切关系。心率变异性检测可以作为运动病易感性重要的预测指标。     

Evaluation of partial k‐space strategies to speed up time‐domain EPR imaging

Narrow‐line spin probes derived from the trityl radical have led to the development of fast in vivo time‐domain EPR imaging. Pure phase‐encoding imaging modalities based on the single‐point imaging scheme have demonstrated the feasibility of three‐dimensional oximetric images with functional information in minutes. In this article, we explore techniques to improve the temporal resolution and circumvent the relatively short biological half‐lives of trityl probes using partial k‐space strategies. There are two main approaches: one involves the use of the Hermitian character of the k‐space by which only part of the k‐space is measured and the unmeasured part is generated using the Hermitian symmetry. This approach is limited in success by the accuracy of numerical estimate of the phase roll in the k‐space that corrupts the Hermiticy. The other approach is to measure only a judicially chosen reduced region of k‐space (a centrosymmetric ellipsoid region) that more or less accounts for >70% of the k‐space energy. Both of these aspects were explored in Fourier transform‐EPR imaging with a doubling of scan speed demonstrated by considering ellipsoid geometry of the k‐space. Partial k‐space strategies help improve the temporal resolution in studying fast dynamics of functional aspects in vivo with infused spin probes. Magn Reson Med 70:745–753, 2013. © 2012 Wiley Periodicals, Inc.     

载人航天空间辐射主动防护方法

近地轨道短期载人航天飞行期间,由于存在地球磁场的保护,舱内航天员受到的空间辐射剂量处于可接受水平,适当的质量厚度屏蔽就可以确保航天员的空间辐射安全。星际飞行中的主要辐射是银河宇宙辐射和随机发生的太阳质子事件。由于缺少了地球磁场的保护,质量厚度屏蔽方法已经不能满足空间辐射防护的需要,必须寻找新的技术和方法解决该问题。本文介绍了国际上主要研究的三种载人航天主动防护方法:静电场防护,等离子体防护和磁场(包括约束磁场与非约束磁场)防护,并分别对它们的防护原理进行了阐述。     

基于Windows 95平台的十二导同步心电图分析系统及其临床测试

目的 为提高心电检测的准确度,在Ｗｉｎｄｏｗｓ９５平台下建立了一个标准十二导心电信号同步检测分析系统。方法 硬件上,采用多处理器的方法,实现二十导心电信号同步采集,以及采集和波形显示的并行操作。软件上,在时域和频域中,分析心电信号的各种不同参数及形态。结果 该系统进行了临床检测和分析,满足了临床的要求。结论 十二导心电信号的同步采集,以及时、频域心电图的同时分析对临床诊断是很有意义的。     

Standardising measurement of tumour vascularity by imaging: recommendations for ultrasound, computed tomography, magnetic resonance imaging and positron emission tomography

This review analyses the need for, and likely impact of, four subsequent papers which discuss the importance of standardisation of ultrasound (US), computed tomography (CT), magnetic resonance imaging (MRI) and positron emission tomography (PET) when assessing tumour vascularity. This is particularly important when measuring the vascular effects of therapeutic agents in oncological research and practice. As imaging inexorably moves from the subjective interpretative art-form of the past into its modern role as a fully fledged objective scientific discipline, it is incumbent on all radiologists to understand the need for strict adherence to perceived best practice when evaluating lesions as part of trials. Indeed trials may only be funded by pharmaceutical companies and other grant-giving bodies if rigorous adherence to imaging protocols and quality assurance is in place. Key Points ? Various imaging methods can now robustly assess tumour vascular support. ? US, CT, MRI and PET are increasingly used to assess tumour vascularity. ? These techniques have reached technical maturity for use in therapeutic oncological trials. ? Consensus guidelines about using these techniques in assessing tumour vascularity are introduced. ? Image acquisition protocols and quality assurance must be established for large trials.     

Time-domain combination of MR spectroscopy data acquired using phased-array coils.

A new method for efficiently processing MRS data acquired with phased-array coils is presented. The method consists of performing phase compensation (i.e., redefining the signal phase relative to a common reference) of the signals in the time domain prior to combining the signals. The resulting spectra are equivalent to those obtained by previously published methods for phased-array spectral data processing (i.e., processing the signals individually and then combining them in the frequency domain). The method allows spectra acquired with phased-array coils to be processed as efficiently as those acquired with non-phased-array coils. Both single voxel spectroscopy (SVS) and chemical shift imaging (CSI) data sets may be processed by this method.     

Space-domain non-iterative approach for SPECT/CT systems considering attenuation and space-variant detector response.

A quantitative analysis of emission planar image reconstruction from projections by an object dependent, exact, direct approach in the space-domain considering both object attenuation and space-variant impulse response of SPECT/CT systems is proposed. That approach is compared with iterative methods and non-object-dependent exact methods in both the space domain and the frequency one. Since the mean-projection precorrection method is the concern of some actual 3D methods of compensation for distance-dependent spatial resolution and is thought right for competing with different methods able to quantify the tracer density in the object of interest, it is also examined in the course of the analysis. The direct approach may also augment the simulation power of the Matlab Image Processing Toolbox concerning the direct and inverse Radon transform from parallel projection data, the Toolbox being actually restricted to the ideal transform in the frequency domain.     

情绪刺激转换对注意转换代价影响的ERP研究

目的 用事件相关脑电位(ERPs)来研究情绪刺激转换对Switch Cost的影响特点。方法 被试者为14名(7男7女)右利手健康大学生。情绪刺激包括表情卡通面孔和中性卡通面孔。采用Garavan的计数双任务范式,要求被试者对刺激序列中表情面孔和中性面孔分别进行计数。记录64导脑电。结果 1)刺激转换与非转换条件下主要区别表现在N2波幅增大及P3波幅下降;2)情绪刺激转换的ERP与无刺激转换的ERP相减所得到的差异波产生了明显的Nd370,主要分布在顶区;3)表情面孔转换为中性面孔的Nd370波幅比中性面孔转换为表情面孔的Nd370要小。结论 顶区分布的Nd370可能是情绪刺激转换的特征性指标,为Switch Cost的理论提供了客观依据。     

Time and frequency domain analysis of NMR data compared: An application to 1D 1H spectra of lipoproteins

A comparison between a time domain analysis algorithm (VARPRO) and a frequency domain analysis algorithm (FITPLA^c) for parameter estimation of magnetic resonance spectroscopy (MRS) data series is presented. VARPRO analyses the measured MRS signal (free induction decay; FID); FITPLA^c analyses the discrete Fourier transform of the FID, the frequency domain magnetic resonance spectrum. A rapid time domain method, used to subtract the dominating water resonance from a ¹H MRS FID, without affecting the metabolites of interest, is outlined and applied. Also a new “pseudo-frequency selective” approach to time domain fitting is introduced. The possibilities of combining the most favorable features of time and frequency domain processing into one single MRS signal processing method are assessed. The ¹H MRS signals of ultracentrifuged very low (VLDL), intermediate (IDL), and high (HDL) density lipoprotein fractions from human blood plasma were used for the comparisons. The results from both algorithms were in good agreement.