不同刺激野的图形翻转视觉诱发电位

目的研究正常人不同刺激野图形翻转视觉诱发电位（pattern reversal visual evoked potentials,PRVEPs）的特点及其法医学应用价值。方法对30名（60眼）正常视功能的受试者分别进行全屏刺激野、中心刺激野及周边刺激野刺激,记录并分析PRVEPs的潜伏期与波幅。结果正常人左、右眼之间PRVEPs各波潜伏期及波幅差异无统计学意义。除中心刺激野PRVEPs中N1波的出现率为36．77％外,各波在不同刺激野PRVEPs的出现率为100％。全屏刺激野与周边刺激野N1波潜伏期差异有统计学意义,波幅差异无统计学意义。P1波潜伏期及波幅在三种不同刺激野PRVEPs中差异均有统计学意义。结论应用不同刺激野的PRVEPs．可对视网膜不同区域的功能状态进行客观评定,并可以用于对受试者是否存在伪装或夸大视野缺损的评定。     

闭合性颅脑损伤后大鼠BAEP及脑损伤的动态变化

目的观察大鼠闭合性弥漫性颅脑损伤后脑干听觉诱发电位(BAEP)的动态改变及脑组织病理学变化,探讨BAEP在颅脑损伤后评估听觉功能障碍的价值。方法使用自制弹簧式小型生物打击机打击大鼠颅顶部,制造闭合性弥漫性轻型颅脑损伤模型。观察对照组以及伤后15min和1,3,6,12h及1,2,4,7,10,14,21d等时间点大鼠脑组织病理学改变,干/湿法检测脑组织含水量。分别于伤前、伤后各时间点以50Hz刺激率记录大鼠BAEP,对其结果进行比较。结果损伤后15min,BAEP的Ⅰ～Ⅴ、Ⅲ～ⅤIPL即较损伤前延长(P<0.05),至6～12h,Ⅲ、ⅤPL较损伤前延长。损伤后1～2d,Ⅲ、ⅤPL和Ⅰ～Ⅲ、Ⅰ～Ⅴ、Ⅲ～ⅤIPL均较损伤前显著延长(P<0.001),14d后BAEP逐渐恢复正常。伤后15min脑组织含水量开始升高,伤后1d达高峰,持续至4d后逐渐下降,至10d后降至正常水平。结论BAEP可作为闭合性弥漫性轻型颅脑损伤后听觉功能障碍的客观评价指标。     

IDENTIFYING MECHANISMS BEHIND POLICY INTERVENTIONS VIA CAUSAL MEDIATION ANALYSIS

Causal analysis in program evaluation has primarily focused on the question about whether or not a program, or package of policies, has an impact on the targeted outcome of interest. However, it is often of scientific and practical importance to also explain why such impacts occur. In this paper, we introduce causal mediation analysis, a statistical framework for analyzing causal mechanisms that has become increasingly popular in social and medical sciences in recent years. The framework enables us to show exactly what assumptions are sufficient for identifying causal mediation effects for the mechanisms of interest, derive a general algorithm for estimating such mechanism‐specific effects, and formulate a sensitivity analysis for the violation of those identification assumptions. We also discuss an extension of the framework to analyze causal mechanisms in the presence of treatment noncompliance, a common problem in randomized evaluation studies. The methods are illustrated via applications to two intervention studies on pre‐school classes and job‐training workshops.     

正常人模式脉冲与模式翻转多焦视诱发电位的比较

目的比较正常人模式脉冲多焦视诱发电位(pattern-pulse multifocal visual evoked potential,PPmf VEP)与模式翻转多焦视诱发电位(pattern-reversal multifocal visual evoked potential,PRmf VEP)的优缺点,观察多焦视诱发电位(mf VEP)的双眼对称性。方法采用Vision Monitor多焦视觉电生理仪检测系统行mf VEP检查,应用t检验和方差分析对两种VEP的主波(P1)、波幅、信噪比及双眼对称性进行统计分析。结果 PPmf VEP与PRmf VEP P1波幅和信噪比均在中央视野最大,并随离心度的增加呈减小趋势,下降速度由快渐趋平缓。在中央视网膜PPmf VEP波幅的变异系数明显小于PRmf VEP,而在周围视网膜则与之相反;PPmf VEP与PRmf VEP双眼对称象限的P1波幅及信噪比差异均无统计学意义(P0.05),双眼同侧象限的波幅差异均大于对称象限。结论 mf VEP能准确、客观地反映视网膜不同部位的视功能;PPmf VEP较PRmf VEP能更好地反映中央视网膜的视功能状况,而在周边视网膜没有优势;在中央视网膜,PPmf VEP较PRmf VEP稳定;而在外周视网膜,PRmf VEP较PPmf VEP稳定;mf VEP在同一个体双眼之间存在对称性。