基于模糊识别理论的针电极肌电信号的辨识

针对针电极肌电信号的不确定性，提出了一种利用模糊识别理论辨识针电极肌电信号的方法，对前臂异常募集时的针电极肌电信号进行辨识，给出了模糊识别所需的特征量，隶属度函数和特征关系矩阵。与选取相同特征值和样本数量的贝叶斯分类器的对比实验表明，这种方法所需样本少，识别准确率高。     

模型生理参数对表面肌电信号影响的仿真研究

通过模型研究肌肉生理参数对表面肌电信号的影响。根据肌肉的形态结构和生理特征,从肌电信号的信号源-细胞内动作电位开始,仿真了单肌纤维动作电位,由此合成了运动单位动作电位,再利用运动单位的募集发放模型,进一步仿真了运动单位动作电位序列,并最终完成了对表面肌电信号的仿真。在此基础上研究了极化区域宽度、跨膜电流密度分布和肌肉组织各向异性3个重要的模型生理参数对表面肌电信号统计特征的影响,得到了一些有价值的结果。实验结果表明,仿真肌电信号能够有效表征肌肉电生理变化过程。     

常运动对大学生Wingate无氧运动能力的影响

目的为研究有规律的运动对大学生无氧运动能力的影响,采用Wingate功率自行车测试比较常运动和久坐大学生的无氧做功能力,并用表面肌电信号分析下肢主要肌群无氧疲劳特征。方法募集38名男大学生,分为常运动和久坐大学生两组,每组各19名。常运动组的质控标准是每周每次运动超过30min、每周运动次数≥4次;0~3次则为久坐组。采用日本COMBI公司PowerMax Ⅶ功率自行车进行Wingate无氧功率测试,比较两组学生最大功率输出(peak power output,PP)、平均功率(mean power output,MP)和无氧疲劳指数(anaerobic fatigue index,AFI)的差异。同时采集了Wingate运动过程中下肢股直肌、股外侧肌、股内侧肌和股二头肌的表面肌电信号,利用自主构建的非线性小波对表面肌电信号的强度和平均功率频率(mean power frequency,MPF)进行分析,检测肌肉纤维的募集与肌肉无氧疲劳状况。结果常运动大学生功率自行车PP和MP显著高于久坐大学生(P0.05),AFI明显小于久坐大学生。肌电信号MPF随着疲劳的产生而持续下降,常运动组的下降趋势比久坐组显著。肌电信号的强度两组也呈现不同的趋势。结论常运动组大学生的无氧运动能力显著高于久坐组。无氧运动能力与快肌纤维密切相关,结合功率输出和肌电信号分析,大学生进行有规律的运动对于增加快肌纤维的比例和面积,并进一步增加肌肉的爆发力和速度有积极的影响。     

基于双谱分析表面肌电信号特征的提取与模式识别

背景:肌电信号在本质上是一种具有非平稳、非高斯特性的生理信号。目前基于高阶累积量的高阶谱技术广泛应用于非高斯、非平稳、非线性等问题。目的:基于非高斯AR参数模型,将双谱分析和fisher线性判别分析方法相结合进行表面肌电信号特征提取。方法:针对表面肌电信号特点,从信号高阶统计处理角度,基于"非高斯AR参数模型"进行双谱分析,提取有效特征,用fisher线性判别分析降维方法构造特征向量,然后利用支持向量机实现不同动作模式的准确分类。并与多种常用表面肌电信号特征的识别准确率进行对比研究。结果与结论:利用多类支持向量机分类器对8种前臂动作进行分类,8种动作的平均识别率达到97.6%以上。通过比较发现,基于短数据的双谱特征在分类性能上优于AR模型系数、小波包系数等构造的特征,能够提高肌电假肢的实时控制的性能。     

快速制动条件下颈部肌肉主动力特性研究EI北大核心

本文研究了快速制动条件下颈部肌肉的主动力特性,可为减少舰载机拦阻着舰时飞行员颈部损伤提供理论支撑。通过开展模拟快速制动条件下的静态加载和实车制动实验,采集受试者头颈部运动状态和颈部肌肉肌电信号,分析颈部肌肉主动力响应特点。结果发现颈部肌肉预紧时头颈部前屈时间推迟、幅度减小;颈部在极限位置持续时间减少,向座椅方向恢复更快;斜方肌比胸锁乳突肌肌电信号更高,可能发挥了更大作用。上述结果提示飞行员在实际制动飞行中可通过预紧颈部肌肉以降低颈部损伤,可以考虑设计颈部肌肉预紧相关装具。     

意外滑动过程中人体下肢关节与肌群的自主平衡调节作用研究

针对受扰条件下的步态失稳现象,国内外学者已做了一定的研究工作,但有关失稳过程中自主平衡行为与表面肌电信号及步态参数之间的表征关系却鲜有涉及。本文将步态分析与肌电信号分析相结合,研究在水平步道行走时,足跟着地后发生意外滑动的情况下,人体下肢关节和肌群的自主平衡调节机制。本文募集10位健康受试者,统一着鞋,采集分析了在干燥步道和油面步道两种不同行走条件下的下肢关节力矩、关节角度和主要参与肌群表面肌电信号等参数的变化规律。研究表明:发生意外滑动时人体通过增大踝关节背屈力矩、髋关节和膝关节伸直力矩与膝关节伸直角度,并及时调整相关肌肉激活延迟时间(依次激活胫骨前肌→股直肌→腓肠肌→股二头肌)来调节身体重心位置以维持平衡、避免滑倒。本文的研究结果可为防止滑跌损伤、康复训练以及下肢助行装置的研发等领域开拓新的思路并提供一定参考价值。     

基于颞肌表面肌电的鼠标装置研究

目的设计一种基于颞肌表面肌电的鼠标装置,用于解决高位截瘫、上肢残疾等手部功能障碍者操作鼠标的难题。方法提出一种基于表面肌电信号控制鼠标的方法,通过分析与试验,选取面部颞肌肌电信号作为控制信息,以咬牙作为触发动作,根据不同咬牙动作时,面部颞肌产生不同的肌电信号特征,设计一种利用颞肌表面肌电信号进行鼠标控制的装置。结果实验结果表明,利用该装置,受试者能够通过简单的咬牙动作实现控制鼠标的目的。结论利用颞肌表面肌电控制鼠标的方法是切实可行的,基于该方法设计的鼠标装置具有较好的应用推广价值。     

利用AR模型提取控制用肌电信号的特征

肌电信号往往作为控制信号源用于肢体运动功能的康复,本文中提出的用AR模型提取肌电信号的特征用于控制目的是一种有效的方法,便于实现多种功能的控制。文中详细介绍了应用快速横向最小二乘(FTF)标法,建立肌电信号AR模型的原理,以及在截瘫病人步行系统中的具体应用。     

基于无线体域网和复合生理信号近似熵的驾驶疲劳研究

为有效合理地评价驾驶员在驾驶过程中的疲劳程度,通过无线体域网(WBAN)采集12名被试者的3种生理信号(脑电信号、肌电信号、呼吸信号),提取并分析这些生理信号的近似熵在驾驶过程中对疲劳程度的反映效果。试验结果表明,脑电、肌电、呼吸3种信号的近似熵均随时间的增加而逐渐下降,约90 min后下降程度变缓,表明进入比较疲劳状态。通过主成分分析可知,前两个主成分的贡献率分别为47.33%和40.26%,二者之和大于85%,其中脑电信号和肌电信号的近似熵所占权重较大。而且统计分析表明,脑电信号和肌电信号的近似熵显著性P＜0.05,表明脑电信号和肌电信号在表征正常与疲劳两种状态时差异明显。在此基础上,分析信号组合对驾驶疲劳的反映效果,结果表明在脑电肌电信号的近似熵组合时,正常和疲劳状态的概率分布具有明显的界限,可以有效反映驾驶过程中的疲劳状态。通过研究,获得最佳的反映疲劳驾驶的信号组合,可为更加准确地检测和避免疲劳驾驶提供理论依据。     

经穴位电刺激下的表面肌电信号特征分析

目的:探究人体穴位电刺激与相关肌肉活动的关系,通过对经穴刺激诱发的表面肌电信号进行特征分析,阐明经穴电刺激下的肌电信号时域、频域特征参数变化与肌肉的激活程度、疲劳程度之间的定量关系,为康复工程和运动医学研究提供参考依据。方法:以8名健康青年志愿者为研究对象,设计穴位电刺激和自主收缩两种实验模式,采集记录两种模式下对应的指伸肌和尺侧腕屈肌的表面肌电信号,提取表面肌电信号均方根值、平均功率频率、中值频率等特征值,并分析其功率谱变化。通过配对t检验,分析经穴电刺激和自主动作模式的肌电信号特征差异。结果:在经穴电刺激模式下,对应的表面肌电信号均方根幅度增大,且经穴电刺激后,肌电信号的谱分布向高频方向移动,肌电的平均功率频率和中值频率随着刺激时间的延长保持稳定。结论:表明对曲池穴和内关穴位电刺激,能够激活对应的指伸肌和尺侧腕屈肌更多的快肌纤维,使肌肉激活程度提高,对缓解肌肉疲劳具有一定作用。     

Surface electromyogram spectral characterization and motor unit activity during voluntary ramp contraction in men

Summary The relationships were investigated between the surface electromyographic (SEMG) power spectrum analysed by the 20 order autoregressive model (AR spectrum) and underlying motor unit (MU) activity during isometric contractions increasing linearly from 0% to 80% maximal voluntary contraction. Intramuscular spikes and SEMG signals were recorded simultaneously from biceps brachii muscle; the former were analysed by a computer-aided intramuscular MU spike amplitude-frequency (ISAF) histogram and the latter subjected to AR spectral analysis. Results indicated that there was a positive correlation between the force output and the mean amplitude of the ISAF histogram but not with the mean frequency. These changes were accompanied by changes in relative power of the high frequency (100–200 Hz) peak (HL) in the AR spectrum. It was also found that there was a positive correlation between the mean amplitude of the ISAF histogram and the HL value. These data suggested that the power of the high frequency peak in the AR spectrum of the SEMG signal preferentially reflected the progressive recruitment of underlying MU according to their size. Differences between the AR spectrum and the spectrum estimated by fast Fourier transform algorithm have also been discussed.     

Effects of Alveolar Recruitment and Positive End-Expiratory Pressure on Oxygenation during One-Lung Ventilation in the Supine Position

Purpose

Hypoxemia during one-lung ventilation (OLV) remains a serious problem, particularly in the supine position. We investigated the effects of alveolar recruitment (AR) and positive end-expiratory pressure (PEEP) on oxygenation during OLV in the supine position.

Materials and Methods

Ninety-nine patients were randomly allocated to one of the following three groups: a control group (ventilation with a tidal volume of 8 mL/kg), a PEEP group (the same ventilatory pattern with a PEEP of 8 cm H₂O), or an AR group (an AR maneuver immediately before OLV followed by a PEEP of 8 cm H₂O). The tidal volume was reduced to 6 mL/kg during OLV in all groups. Blood gas analyses, respiratory variables, and hemodynamic variables were recorded 15 min into TLV (TLV_baseline), 15 and 30 min after OLV (OLV₁₅ and OLV₃₀), and 10 min after re-establishing TLV (TLV_end).

Results

Ultimately, 92 patients were analyzed. In the AR group, the arterial oxygen tension was higher at TLV_end, and the physiologic dead space was lower at OLV₁₅ and TLV_end than in the control group. The mean airway pressure and dynamic lung compliance were higher in the PEEP and AR groups than in the control group at OLV₁₅, OLV₃₀, and TLV_end. No significant differences in hemodynamic variables were found among the three groups throughout the study period.

Conclusion

Recruitment of both lungs with subsequent PEEP before OLV improved arterial oxygenation and ventilatory efficiency during video-assisted thoracic surgery requiring OLV in the supine position.     

β ‐Adrenoceptor agonist sensitizes the dopamine‐1 receptor in renal tubular cells

The renal effects of dopamine are mainly mediated via the dopamine‐1 receptor (D1 receptor). This receptor is recruited from intracellular compartments to the plasma membrane by dopamine and atrial natriuretic peptide (ANP), via adenylyl cyclase activation. We have studied whether isoproterenol, a β‐adrenoceptor (β‐AR) agonist that may interact with dopamine in the regulation of rat renal Na+, K⁺‐adenosine triphosphatase (ATPase) activity, can recruit D1 receptors to the plasma membrane. The spatial regulation of D1 receptors was examined using confocal microscopy techniques in LLCPK cells and the functional interaction between dopamine and isoproterenol was examined by studying their effects on Na+, K⁺‐ATPase activity in microdissected single proximal tubular segments from rat. Isoproterenol was found to translocate the D1 receptors from the interior of the cell towards the plasma membrane. The recruitment of dopamine 1 receptors was found to be cyclic adenosine phosphate (cAMP) dependent, while protein kinase C (PKC) activation was not involved. The functional studies on Na+, K⁺‐ATPase activity showed that the effect of isoproterenol was abolished by a D1‐like receptor antagonist (SCH 23390), and mediated via protein kinase A (PKA) and PKC dependent pathways. The results provide an explanation for the interaction between G protein‐coupled receptors. The effects of isoproterenol on Na+, K⁺‐ATPase activity can be explained by a heterologous recruitment of D1 receptors to the plasma membrane.     

某市招警MMPI测验结果分析

目的研究警察招募报名者的人格特征,获得录取决策的依据。方法采用MMPI对招警报名者进行心理测试,对测试结果进行聚类分析和方差分析。结果男女受试者人格特征相似,L、K、Hy和Ma为T高分点,女性Mf也是T高分点;聚类分析将报名者分为3类,在录取决策中予以不同的加权。结论心理测试可以作为录取决策的指标并能反映出警察的一些人格特征。     

The Differential Role of Verbal and Spatial Working Memory in the Neural Basis of Arithmetic

We examine the relations of verbal and spatial working memory (WM) ability to the neural bases of arithmetic in school-age children. We independently localize brain regions subserving verbal versus spatial representations. For multiplication, higher verbal WM ability is associated with greater recruitment of the left temporal cortex, identified by the verbal localizer. For multiplication and subtraction, higher spatial WM ability is associated with greater recruitment of right parietal cortex, identified by the spatial localizer. Depending on their WM ability, children engage different neural systems that manipulate different representations to solve arithmetic problems.     

Neuron production, neuron number, and structure size are seasonally stable in the hippocampus of the food-storing black-capped chickadee (Poecile atricapillus)

Neuronal recruitment in the black-capped chickadee (Poecile atricapillus) hippocampus occurs at a higher rate in the fall than at other times of the year. As a means of determining whether this increase in recruitment results from greater neuron production, chickadees were caught in the wild between October and March and injected with the cell-birth marker 5-bromo-2'-deoxyuridine. Two weeks later, birds were killed by overdose, and hippocampal neuron production, apoptosis, neuron number, and hippocampal volume were determined. Chickadees collected in October, November, January, February, and March did not differ in neuron production, apoptosis, hippocampal volume, or neuron number. These findings indicate that increases in neuronal recruitment in the chickadee hippocampus in the fall do not result from increased neuron production, but instead, enhanced survival of new neurons.     

Motion selectivity in macaque visual cortex. II. Spatiotemporal range of directional interactions in MT and V1

We measured the spatial and temporal limits of directional interactions for 105 directionally selective middle temporal (MT) neurons and 26 directionally selective striate (V1) neurons. Directional interactions were measured using sequentially flashed stimuli in which the spatial and temporal intervals between stimuli were systematically varied over a broad range. A direction index was employed to determine the strength of directional interactions for each combination of spatial and temporal intervals tested. The maximum spatial interval for which directional interactions occurred in a particular neuron was positively correlated with receptive-field size and with retinal eccentricity in both MT and V1. The maximum spatial interval was, on average, three times as large in MT as in V1. The maximum temporal interval for which we obtained directional interactions was similar in MT and V1 and did not vary with receptive-field size or eccentricity. The maximum spatial interval for directional interactions as measured with flashed stimuli was positively correlated with the maximum speed of smooth motion that yielded directional responses. MT neurons were directionally selective for higher speeds than were V1 neurons. These observations indicate that the large receptive fields found in MT permit directional interactions over longer distances than do the more limited receptive fields of V1 neurons. A functional advantage is thereby conferred on MT neurons because they detect directional differences for higher speeds than do V1 neurons. Recent psychophysical studies have measured the spatial and temporal limits for the perception of apparent motion in sequentially flashed visual displays. A comparison of the psychophysical results with our physiological data indicates that the spatiotemporal limits for perception are similar to the limits for direction selectivity in MT neurons but differ markedly from those for V1 neurons. These observations suggest a correspondence between neuronal responses in MT and the short-range process of apparent motion.     

Using Google AdWords for International Multilingual Recruitment to Health Research Websites

Background

Google AdWords, the placement of sponsored links in Google search results, is a potent method of recruitment to Internet-based health studies and interventions. However, the performance of Google AdWords varies considerably depending on the language and the location of the target audience.

Objective

Our goal was to describe differences in AdWords performance when recruiting participants to the same study conducted in four languages and to determine whether AdWords campaigns can be optimized in order to increase recruitment while decreasing costs.

Methods

Google AdWords were used to recruit participants to the Mood Screener, a multilingual online depression screening tool available in English, Russian, Spanish, and Chinese. Two distinct recruitment periods are described: (1) “Unmanaged”, a 6-month period in which ads were allowed to run using only the AdWords tool itself, with no human intervention, and (2) “Managed”, a separate 7-week period during which we systematically sought to optimize our recruitment campaigns.

Results

During 6 months of unmanaged recruitment, our ads were shown over 1.3 million times, resulting in over 60,000 site visits. The average click-through rate (ratio of ads clicked to ads displayed) varied from 1.86% for Chinese ads to 8.48% for Russian ads, as did the average cost-per-click (from US $0.20 for Chinese ads to US $0.50 for English ads). Although Chinese speakers’ click-through rate was lowest, their rate of consenting to participate was the highest, at 3.62%, with English speakers exhibiting the lowest consent rate (0.97%). The conversion cost (cost to recruit a consenting participant) varied from US $10.80 for Russian speakers to US $51.88 for English speakers. During the 7 weeks of “managed” recruitment, we attempted to improve AdWords’ performance in regards to the consent rate and cost by systematically deleting underperforming ads and adjusting keywords. We were able to increase the number of people who consent after coming to the site by 91.8% while also decreasing per-consent cost by 23.3%.

Conclusions

Our results illustrate the need to linguistically and culturally adapt Google AdWords campaigns and to manage them carefully to ensure the most cost-effective results.