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。     

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。     

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。     

模拟失重条件下与选择心算关联的脑电位的动态变化

为研究模拟失重对脑功能状态的影响，在１５名正常被试者中比较了头低位倾斜－１０°（ＨＤＴ，模拟失重）和头高位倾斜＋２０°（ＨＵＴ，对照）条件下视觉选择心算的事件关联电位（ＥＲＰｓ），在每种体位的２ｈ期间各进行５套测试。结果表明：靶和非靶闪光信号引起不同的正慢电位；靶信号的正慢电位时程和幅值显著长于和高于非靶信号，尤以后脑区为最；与ＨＵＴ比较，在ＨＤＴ条件下正慢电位的幅值降低，且在第４及第５套记录时更明显。提示模拟失重对高级脑功能有一定的影响     

模拟失重条件下与视觉注意关联的脑电位变化

为研究模拟失重对脑功能状态的影响，在９名正常被试者中比较了头低位倾斜（ＨＤＴ－模拟失重）和头高位倾斜（ＨＵＴ，对照）条件下视觉选择反应了事件关联电位（ＥＲＰｓ）。主要结果为：靶非靶闪光信号均引起显著的正慢电位；与ＨＵＴ比较，在ＨＤＴ条件下额区的正慢电位幅值显著下降且在非靶反应中更为突出，由于上述正慢电位可能与视觉选择反应中的注意过程有关，本文结果表明，在模拟失重条件下脑的功能状态发生明显变化，表现     

头低位卧床对眼内压、近视力、视野的影响及其中药防护

目的观察头低位卧床模拟失重对人体眼压、视野、近视力的影响 ,及中药对抗模拟失重的效果。方法 1 0名被试者随机分成对照组和中药组 ,用头低位 - 6° 2 1d卧床模拟失重 ,分别于卧床前、中、后测量两组被试者眼内压、近视力及视野。结果眼内压及近视力在卧床期间呈波动下降趋势 ,两者间存在一定相关性 ;中心视野变化无显著性 ;服中药可在一定程度上防止近视力下降。结论 1 )头低位卧床可引起眼压、近视力下降 ;2 )服中药可在一定程度上对抗模拟失重对近视力的不良影响     

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     

听觉事件相关电位(ERPs)早期和晚期成份的任务负荷效应

目的 比较不同任务负荷的听觉事件相关电位（ERPs,event-related potentials)，以探讨听觉ERPs各种成份的任务负荷效应。方法 被试者为12名右利手正常在校大学生（20－23岁）。要求被试者对4个方位的声音信号进行难度负荷不同的3种作业任务：全反应（AR）、方位区分反应（DR）、音调选择方位式区分反应（SR）。对－t和方差分析统计3种任务的听觉ERPs成份。结果1）SR反应时最长，DR次之，AR最短；2）早期成份的任务负荷效应：P1波幅随负荷的增加进行性增强；AR－ERPs的NI峰值相近，均高于SR（T）－ERPs；DR－ERPs与SR（T）－ERPs中前脑区的P2波幅无明显差异，均显著低于AR－ERPs，P2的潜伏期随负荷的增加明显缩短；3）晚期成分的任务负荷效应；随任务负荷的增加，N2（N2a/N2b),P3和SW波幅明显增强。结论 听觉ERPs早期成份和晚期成份均有明显的任务负荷效应，晚期成份的任务负荷效应可能与早期的警觉激活程度相关联。     

头低位卧床模拟失重对汉语语音特征的影响

目的探讨头低位卧床模拟失重作用下生成语音的语音特征的变化规律。方法被试者为 6名健康男性青年 ,头低位 - 6°模拟失重条件下记录语音特征及变化规律。结果与对照组相比 ,模拟失重作用下语音的时长有一定增加 ;平均能量明显降低 ,结果非常显著 ;基频有一定降低 ,并有显著性差异 (P <0 .0 5)。结论模拟失重对人的语音特征产生一定影响 ,某些语音特征的影响具有显著性。     

间断性头高位45°对模拟失重兔股静脉顺应性的影响

目的观察间断性头高位45°锻炼对模拟失重兔股静脉应力-应变关系的影响。方法采用兔头低位-20°倾斜的方法模拟失重。24只雄性健康兔,随机分为对照组、模拟失重21d组(HDT)和每天2h头高位45°对抗组(HUT),每组8只。实验21d后测试离体股静脉轴向和环向应力-应变关系的变化。结果在相同应力下,模拟失重组兔股静脉环向加、卸载形变较对照组均显著增加(P<0·05或P<0·01),而轴向加、卸载形变较对照组均无明显变化。对抗组与模拟失重组相比,在同等应力情况下,环向形变明显减小(P<0·05或P<0·01),轴向形变无明显变化。对抗组与对照组相比,轴向及环向形变均无显著差异。结论21d模拟失重可引起兔股静脉顺应性显著增加,每天2h头高位45°锻炼可部分对抗模拟失重所引起的股静脉顺应性的增加。     

极低频磁场刺激对模拟失重条件下选择心算脑反应的影响

目的探讨极低频磁场（ＥＬＭＦ）在航天医学中的可能应用价值。方法在４０名２０～２５岁健康男性青年中,比较了头低位－１０°（ＨＤＴ）模拟失重条件下５Ｈｚ的ＥＬＭＦ刺激前后选择心算事件关联电位（ＥＲＰｓ）的变化。结果对照组ＥＲＰｓ中的正慢电位（主要位于后脑区）随头低位时间的延长,幅值呈现进行性下降趋势;ＥＬＭＦ组在ＥＬＭＦ刺激前后此正慢电位未出现明显的下降趋势,表明ＥＬＭＦ刺激抑制了模拟失重期间选择心算ＥＲＰｓ中正慢电位的下降。此正慢电位可能反映了一种集中注意对信号进行分析处理的主动脑抑制过程。结论所用的ＥＬＭＦ刺激在一定程度上可以改善模拟失重条件下的脑功能状态     

Different responses of cerebral vessels to -30 degrees head-down tilt in humans.

This study explored changes of the cerebral circulation and evaluated the responses to weightlessness in 12 volunteers (18-22 yr of age). The velocities, diameters and blood flow volume of the common carotid artery (CCA), internal carotid artery (ICA), vertebral artery (VA) and internal jugular vein (IJV) were measured with color Doppler echogram before and during simulated weightlessness. -30 degrees head-down tilt (HDT) for 45 min was used as a weightlessness simulation model. When the subjects' positions were changed from the supine to -30 degrees HDT, blood flow velocities along the CCA, ICA and IJV decreased significantly (p< 0.05), and their diameters were increased. The subjects were divided into two groups according to measured changes in flow volume of the ICA and IJV: group I with a net in-flow of cerebral blood flow (CBF) and group II with a net out-flow of CBF during HDT. Symptoms were recorded in the two groups during HDT (nasal congestion, sensation of head fullness, headache, and others) and graded on a four-point scale, from absent to serious. Results showed that group I had a higher symptoms score while group II had a lower symptoms score. Although this difference did not reach statistical significance, it suggests that cerebral blood flow changes may be partly responsible for the symptoms observed in subjects during HDT.     

头低位倾斜条件下视觉选择反应关联的正慢电位变化的时间 …

The temporal and spatial features of visual ERP changes during 2 hour HDT (-10 degrees) were compared with that during HUT (+20 degrees) in 15 normal subjects. The stimuli consisted of two color LED flashes appeared randomly in left (LVF) or right (RVF) visual field with the same probability. The subjects were asked to make switch response to target signals (T) differentially: switching to left for T in LVF and to right for T in RVF, and making no response to non-target signals (N). Five sets of tests were made during HUT and HDT. ERPs were obtained from 9 locations on the scalp. Mean amplitude of the ERPs in the period 0.30-0.55 s were taken as the amplitude of slow positive potential (P400). The results obtained were: (1) The mean amplitude of P400 decreased during HDT which was more significant at the 2nd, 3rd and 5th set of tests; (2) spatially, the reduction of mean P400 amplitude during HDT was more significant for signals from RVF and were more significant at posterior and central brain regions than those from frontal locations. These data provide further evidence showing that the higher brain function was affected by the simulated weightlessness and that this effect was not only transient but also with interesting spatial characteristics.     

不同认知水平条件下左右脑对左右视场信号的不对称反应特征

目的探讨在认知活动中左右脑对左右视场(LVF,RVF)信号的反应特性. 方法对23名被试者在3种任务条件下9个部位的与LVF和RVF相应的事件关联电位(ERPs)进行了比较.刺激信号为位于LVF和RVF中的红、绿闪光,等概率随机出现,交叉地规定红或绿闪光为靶信号(T).3种任务是:视对照(VC);简单选择反应(SR);选择区分反应(DR),对LVF和RVF的T分别向左和右拨开关. 结果 (1)除外源性的P1和N1成分外,与LVF和RVF相应的ERPs的差别突出地表现在左额区(F5),即在SR和DR条件下RVF的T-ERPs及NT-ERPs中出现显著的负慢波,而右脑对信号的方位不敏感;(2)左右脑对LVF和RVF信号反应的不对称性与认知状态有关:靶信号时与对侧视场相应的ERPs左脑比右脑显著偏负,而非靶信号则是与同侧视场相应的ERPs在左、右脑出现显著差别,且是右脑(F5,C5)偏负. 结论左右脑对靶和非靶信号的反应不同提示二者在信号加工过程中的不同功能;左额区对RVF中靶和非靶信号的负慢电位反应提示右视场中具有心理意义的信号可能引起较大的心理负荷.     

The effects of head-down tilt on carotid blood flow and pulmonary gas exchange

Common carotid artery blood flow (CCF), pulmonary gas exchange and ventilation were measured in six subjects in the supine posture (SUP I), serially during 20 min of head-down tilt at -30 degrees (HDT) and after returning to the supine posture (SUP II). CCF was approximately 6% lower during HDT, with a transient increase during the second minute, and was about 7% higher during SUP II than during SUP I. The transition from SUP I to HDT caused increases in O2 uptake (VO2), CO2 output, respiratory exchange ratio and tidal volume in the first minute. Similar responses were apparent following the HDT to SUP II transition, except for VO2, which changed little. Correction of VO2 for changes in estimated lung O2 stores indicated that about 200 ml of blood were shifted within the circulation by the tilt transitions which provided a ventilatory stimulus. HDT can cause a loss in blood and tissue O2 stores and gain in CO2 stores by shifting blood volume toward and blood flow away from the dependent headward vascular compartment and perhaps by producing ischemia in the elevated lower extremities. Cerebral venous congestion during HDT appears to cause periodic breathing and reduce CCF, the latter being partially offset by reduced flow resistance in the carotid artery.