正常人不同视差刺激时静态视差诱发电位分析

用静态随机点立体图作视刺激，对40名正常人在不同视差(2'、7'、14'，23'、36'，46'、92'、138'和230')状态下进行视诱发电位检测。 结果：不同视差刺激时在250m左右记录到宽大的正波(即P₂₅₀波)；精细视差(<23')和粗略视差(246')刺激时的诱发电位波形不同，分别出现一次振幅高峰，揭示人类立体视觉存在相互独立的精细与粗略视差加工机制． （中华眼底病杂志，1995，11：155-158）     

随机点立体图刺激引起的立体视觉诱发电位

应用自制电视静态随机点立体图（ＴＶ－ｓｔａｔｉｃｒａｎｄｏｍｄｏｔｓｓｔｅｒｅｏｇｒａｍ，ＴＶ－ＳＲＤＳ）作视差刺激，记录了３５例正常人用三棱镜破坏与不破坏立体视时，１６．５６＇视差刺激的ＶＥＰ和２８例立体视盲者该视差刺激的ＶＥＰ。结果：（１）３３例正常人于刺激后恒定出现一负正复合波；（２）用三棱镜破坏立体视，ＶＥＰ波形消失；（３）立体视盲组，除１例麻痹性斜视外，均未记录到电位变化。作者认为：本实验条件下ＴＶ－ＳＲＤＳ刺激产生的ＶＥＰ是与视差刺激相关的特异性ＶＥＰ，ＴＶ一ＳＲＤＳ是以电生理方法客观测定立体视的有效刺激，是探讨立体视觉的发生、发育的一种方法。     

动态随机点立体图视差诱发电位的研究

目的从电生理学角度探讨立体视的机制,为客观检测立体视提供参数。方法由微机产生动态随机点立体图刺激,记录30名近距离立体视健康成年人4′-150′不同大小交叉和非交叉引起的视差诱发电位（disparity evoked potential,DEP）。结果（1）不同视差的DEP均为宽大负正波;（2）45′交叉视差DEP的N波潜伏时最长,150′的N波潜伏时最短;4′和30′非交叉视差DEP的N波潜伏时最长,124′的N波潜伏时最短;（3）交叉视差DEP的P波振幅高峰出现在23′、60′及150′,非交叉视差DEP出现在15′、45′及72′;（4）各视差DEP的N波潜伏时、P波振幅的非交叉视差变化曲线较交叉视差整体性左移;小视差的交差视差与非交差视差DEP的N波潜伏时演变规律不同。结论DEP的N波潜伏时、P波振幅能够为客观检测立体视提供参数;立体视宜分为精细交叉与精细非交叉、粗略交叉与粗略非交叉立体视。（中华眼科杂志,2006,42：878-882）     

屈光不正者的视差诱发电位检测

目的 应用视差诱发电位检查探讨屈光不正对立体视功能的影响及其机制。方法 用新型静态随机点立体图深度翻转作视刺激，对21名屈光不正者（屈光度>±0.75D，≤±8.00D）和40名正常人进行视差诱发电位检测。 结果 在不同视差刺激时屈光不正者与正常人一样均可记录到与立体刺激相关的宽大正波（即P₂₅₀波）；随视差的增大P₂₅₀波形和振幅发生相应的变化，变化的特征与正常人相类似；近视与远视者的视差诱发电位P₂₅₀波振幅和潜伏时无明显差别。 结论 在一定屈光范围内的屈光不正经完全矫正后对立体视功能没有明显的影响。 (中华眼底病杂志,1998,14:225-227)     

外斜视动态随机点立体图刺激所引发的立体视觉诱发电位之特性

目的：应用动态随机点立体图形刺激方法及VEP记录方法,了解外斜视患者动态随机点体图刺激所引发的立体视觉诱发电位特性。方法：应用自制的动态随机点立体图（DRDS-Dynamic Random Dot Stereop-sis）做视刺激系统,记录30例正常人及27例外斜视患者双眼及单眼观察DRDS的立体视觉诱发电位（VEP）。结果：（1）30例正常人在刺激双眼后均记录到一恒定的负正复合波,但在刺激单眼后均未记录到电位变化。（2）27例外斜视患者刺激双眼后和刺激单眼后均未记录到电位变化。结论：在本实验条件下,以动态随机点立体图做视刺激所产生的VEP是由视差刺激所引起的特异性VEP,可以认为这种DRDS刺激是测定立体视的有效刺激,是探讨立体视觉发生、发育的一种方法。外斜视患者虽然有双眼视及立体视存在,但其双眼视及立体视与正常人有一定的区别,特别是视皮层双皮信息加工中枢的不同信息反应,有待于进一步的研究。     

屈光参差者视差诱发电位检测的研究

探讨屈光参差对立体视功能的影响及其机制。方法以新型静胡机点立科（ｒａｎｄｏｍ－ｄｏｔ ｓｔｅｒｅｏｇｒａｍｓ,ＲＤＳ）深度翻转作视刺激,对２０例屈光参差者和４０例正常人进行视差诱发电位（ｄｉｓｐａｒｉｔｙ ｅｖｏｋｅｄ ｐｏｔｅｎｔｉａｌｓ,ＤＥＰ）检测。结果屈光参差者在不同视差刺激时可记录到与立体刺激相关的波形（即Ｐ２５０波）,但其振幅的增长与平面图形的比值显著低于正常人（Ｐ〈０．０５）;重度屈     

正常人视觉诱发电位的特征

目的:探讨正常人视觉诱发电位(visualevokedpotential,VEP)的特征,以获得正常参考值。方法:应用法国Metrovision公司生产的VisionMonitor视觉诱发系统对正常人60例(73眼)在白色、红色和蓝色闪光刺激下进行闪光VEP检查,按年龄不同分成4组:A组(5～14岁)19眼,B组(15～29岁)17眼,C组(30～49岁)21眼,D组(50～65岁)16眼;对正常人62例(77眼)在15,30和60min视角黑白棋盘格翻转图形刺激下进行图形VEP检查。按年龄不同分成4组:A组(5～14岁)20眼,B组(15～29岁)20眼,C组(30～49岁)22眼,D组(50～65岁)15眼。结果:在白色、红色、蓝色闪光刺激下P2波的潜伏期分别为122.2±8.3,122.5±11.7,124.1±8.5ms;在白光刺激下D组P2波的潜伏期与其他各年龄组相比,均有差异(P<0.05)。其他各年龄组相互比较,均无显著意义。在红光和蓝光刺激下A组与D组比较,A组、D组与其他年龄组比较均延长,有显著意义(P<0.05),其他各年龄组相互比较,均无显著意义。在15',30'和60'视角黑白棋盘格翻转图形刺激下P100波的潜伏期分别为111.6±6.0,105.9±5.3,105.1±3.8ms。各年龄组图形VEP相比较均无显著意义(P>0.05)。结论:在白色、红色和蓝色闪光刺激下14岁以下年龄组和50岁以上年龄组闪光VEPP2波的潜伏期较其他组延长,图形VEPP100波的潜伏期各年龄组比较无显著差异。     

间歇性外斜视患者交叉视差和非交叉视差的临床观察

目的　了解间歇性外斜视患者交叉视差和非交叉视差的临床变化。方法　对 5 5例间歇性外斜视患者 ,术前应用颜少明的《立体视觉检查图》检测其近零视差、交叉视差及非交叉视差 ,并根据检测情况分为 3组进行分析。结果　第 1组 2 5例 ,近零视差立体视锐度正常者占 4 8 0 % ,其交叉视差和非交叉视差立体感知度检测值均不在正常范围 ,交叉视差者的立体感知度检测值比非交叉视差者大 ,差异有显著意义 (t =84 3 5 ,P <0 0 0 0 1)。第 2组 2 6例 ,近零视差立体视锐度正常者占30 8% ,其交叉视差立体感知度检测值不在正常范围 ,未见有非交叉视差者。第 3组 4例 ,为仅查到不正常的近零视差立体视锐度者。 5 5例中 ,无近零视差仅和非交叉视差共存者 ,也无交叉视差和非交叉视差各自独立存在者 ,亦无交叉视差和非交叉视差两者共存者。结论　 (1)本组间歇性外斜视患者近零视差立体视锐度及交叉视差和非交叉视差立体感知度不健全 ;(2 )间歇性外斜视患者视差的损害顺序依次为非交叉视差、交叉视差、近零视差。 (3)双眼黄斑颞侧视网膜对应的是交叉视差 ,双眼黄斑鼻侧视网膜对应的是非交叉视差     

间歇性外斜视不同视差立体视的临床观察

目的 了解间歇性外斜患者不同立体视觉的临床变化.方法 对38例间歇性外斜患者,屈光矫正后,采用颜少明<数字化立体视觉检查图-2006年版>行近零视差立体视敏度、交叉视差和非交叉视差立体视检查,Titmus立体视检查,采用同视机随机点市体视画片检查远立体视.对检测结果进行分析.结果 (1)具有可测得的远立体视,即同视机随机点立体视的患者13例(34%),并且均有正常的近零视差、交叉视差、非交叉视差的立体视觉.即:Titmus为40"或60";RDS为40"或60";交叉视差、非交叉视差均≥600".(2)未检测出远立体视患者25例(66%).其中:①近零视差Titmus和RDS为40"或60"患者14例,且均有正常的交叉视差、非交义视差的立体视觉.②近零视差RDS>60"患者11例.其中非交叉视差正常4例,交义视差亦正常;非交叉视差异常7例,有正常的交叉视差者2例,交义视差异常5例.未出现非交叉视差正常而交叉视差异常者.近零视差立体视正常者的交叉/非交叉正常检出率明显高于近零视差异常者(P=0.001).结论 此研究推测各种立体视易受损害程度顺序可能为:远立体视>近零视差>非交叉视差>交叉视差立体视觉.符合精细立体视先于粗放立体视受损.     

发育期单眼形觉剥夺弱视模型猫P-VEP的特征

目的 观察单眼形觉剥夺性弱视动物模型视皮层的电生理特性,探索弱视发生的皮层机制,并为弱视的治疗提供实验依据.方法 11只初生家养猫随机分为2组,处理组在3周龄时缝合单侧眼睑塑造单眼形觉剥夺性弱视模型,3个月后以图形视觉诱发电位(pattern visual evoked potential,P-VEP)技术检测视觉生理功能的改变.结果 对照组双眼间的P-VEP波形潜伏时和振幅差异无统计学意义(P>0.05),而处理组剥夺眼的P波潜伏时延迟和振幅降低或呈波形熄灭的杂波,与对侧健眼及对照组比较,差异均具有显著统计学意义(0.01相似文献   

The Analysis of Disparity Evoked Potentials by a New Form of Static Random—Dot Stereograms

Purpose :A new form of static random-dot stereograms free of monocular clues was designed as stimulus to elicit disparity evoked potentials. Methods:Disparity evoked potentials were recorded in 40stereo-normal subjects. The stimulator was a white-black static random-dot stereograms generated by a computer and had no monocular clues. Every subject was tested in disparity stimulus, zero disparity stimulus, monocular stimulus and wearing prism condition. Results: A characteristic wide positive wave at about 250 ms was consistantly recorded in disparity stimulus,which may be regarded as evidence of the the presence of stereopsis. In contrast, recordings for zero disparity stimulus, monocular vision, stimulus and wearing prism condition all demonstrated a markedly difference from recording for disparity stimulus. Eye Science 1995; 11:48- 52.     

Visual evoked potentials to red-green stimulation in schoolchildren

The aim is to study chromatic visual evoked potentials (VEP) to isoluminant red-green (R-G) stimulus in schoolchildren. Sixty children (7-19 years) with normal color vision were examined, 30 binocularly and 30 monocularly. The isoluminant point was determined for each child subjectively by using heterochromatic flicker photometry, and objectively from recordings. The stimulus was a 7 degrees circle composed of horizontal sinusoidal gratings, with spatial frequency 2 cycles/degrees and 90% contrast, presented in onset-offset mode. VEP were recorded from Oz (mid-occipital) position. Age-dependent waveform changes and changes of the positive and negative wave were studied to both binocular and monocular R-G stimulation. Age-dependent waveform changes were observed to binocular and monocular R-G stimulation. In younger children the positive wave was prominent, whereas in older children also the negative wave became more evident. The latency of the positive wave decreased linearly with age to R-G binocular stimulation. To monocular stimulation no significant changes of the latency were observed. The amplitude of the positive wave dropped exponentially with age to binocular and monocular stimulation. The latency of the negative wave increased linearly with age to binocular and monocular stimulation, whereas the amplitude did not show age-dependent changes. These findings suggest that the chromatic VEP response undergoes evident age-dependent changes during the school-age period.     

Apparent motion of monocular stimuli in different depth planes with lateral head movements

A stationary monocular stimulus appears to move concomitantly with lateral head movements when it is embedded in a stereogram representing two front-facing rectangular areas, one above the other at two different distances. In Experiment 1, we found that the extent of perceived motion of the monocular stimulus covaried with the amplitude of head movement and the disparity between the two rectangular areas (composed of random dots). In Experiment 2, we found that the extent of perceived motion of the monocular stimulus was reduced compared to that in Experiment 1 when the rectangular areas were defined only by an outline rather than by random dots. These results are discussed using the hypothesis that a monocular stimulus takes on features of the binocular surface area in which it is embedded and is perceived as though it were treated as a binocular stimulus with regards to its visual direction and visual depth.     

Stereomotion speed perception: contributions from both changing disparity and interocular velocity difference over a range of relative disparities

The role of two binocular cues to motion in depth-changing disparity (CD) and interocular velocity difference (IOVD)- was investigated by measuring stereomotion speed discrimination and static disparity discrimination performance (stereoacuity). Speed discrimination thresholds were assessed both for random dot stereograms (RDS), and for their temporally uncorrelated equivalents, dynamic random dot stereograms (DRDS), at relative disparity pedestals of -19, 0, and +19 arcmin. While RDS stimuli contain both CD and IOVD cues, DRDS stimuli carry only CD information. On average, thresholds were a factor of 1.7 higher for DRDS than for RDS stimuli with no clear effect of relative disparity pedestal. Results were similar for approaching and receding targets. Variations in stimulus duration had no significant effect on thresholds, and there was no observed correlation between stimulus displacement and perceived speed, confirming that subjects responded to stimulus speed in each condition. Stereoacuity was equally good for our RDS and DRDS stimuli, showing that the difference in stereomotion speed discrimination performance for these stimuli was not due to any difference in the precision of the disparity cue. In addition, when we altered stereomotion stimulus trajectory by independently manipulating the speeds and directions of its monocular half-images, perceived stereomotion speed remained accurate. This finding is inconsistent with response strategies based on properties of either monocular half-image motion, or any ad hoc combination of the monocular speeds. We conclude that although subjects are able to discriminate stereomotion speed reliably on the basis of CD information alone, IOVD provides a precise additional cue to stereomotion speed perception.     

Slant perception, and its voluntary control, do not govern the slant aftereffect: multiple slant signals adapt independently

Although it is known that high-level spatial attention affects adaptation for a variety of stimulus features (including binocular disparity), the influence of voluntary attentional control-and the associated awareness-on adaptation has remained unexplored. We developed an ambiguous surface slant adaptation stimulus with conflicting monocular and binocular slant signals that instigated two mutually exclusive surface percepts with opposite slants. Using intermittent stimulus removal, subjects were able to voluntarily select one of the two rivaling slant percepts for extended adaptation periods, enabling us to dissociate slant adaptation due to awareness from stimulus-induced slant adaptation. We found that slant aftereffects (SAE) for monocular and binocular test patterns had opposite signs when measured simultaneously. There was no significant influence of voluntarily controlled perceptual state during adaptation on SAEs of monocular or binocular signals. In addition, the magnitude of the binocular SAE did not correlate with the magnitude of perceived slant. Using adaptation to one slant cue, and testing with the other cue, we demonstrated that multiple slant signals adapt independently. We conclude that slant adaptation occurs before the level of slant awareness. Our findings place the site of stereoscopic slant adaptation after disparity and eye posture are interpreted for slant [as demonstrated by Berends et al. (Berends, E. M., Liu, B., & Schor, C. M. (2005). Stereo-slant adaptation is high level and does not involve disparity coding. Journal of Vision 5 (1), 71-80), using that disparity scales with distance], but before other slant signals are integrated for the resulting awareness of the presented slant stimulus.     

Evoked potentials to dynamic random dot stimuli with varying dot density ratios of disparity to background

A systematic study was made of visual evoked responses to dynamic random dot stimuli containing controllable, monocularly visible contrast cues. Ratios of dot densities for the centrally presented, disparate figure and the background were varied in steps of 1/8 maximum density between 0/8 and 8/8. The figure was either a square or an equivalent area of nebulous shape. A 30-arc min disparity was compared with binocular nondisparate and monocular conditions. Evoked responses (scalp sites 02, 01, T6, T5) were averaged for each of 24 disparity-contrast-shape conditions. At all contrast levels, response amplitudes and latency over the left hemisphere was significantly greater than over the right hemisphere. For 30 arc min disparity, amplitudes in the 8/8 condition were significantly smaller than in conditions where stimulus/background contrast could afford monocular depth cues. Hemisphere amplitude differences diminished as contrast decreased. Factor analyses isolated two overlapping components in the response to disparate stimuli. The earlier, at 236 ms latency, may index the stereoscopic stimulus features. The later, at 295 ms, peaking at maximum contrast and present in all suprathreshold nondisparity conditions, may index contrast features of the stimulus. The results indicate the importance of controlling dot density ratios in electrophysiological studies of the stereoscopic response to random dot stimuli.     

Stereopsis without binocular correlation

In a simple stimulus environment, a diplopic stereoscopic pair gives the same apparent depth whether the pair consists of similar or dissimilar images. This apparent depth may arise in part from a direct comparison of the two eyes images, but it may also be based in part on a process that assigns depth to monocular stimulation on the basis of retinal location: briefly presented monocular stimuli within the nasal retina (temporal field) appear to be more distant than stimuli presented within the temporal retina (nasal field). A model is presented which shows that such a monocular depth response could result from the inadequate stimulation of disparity detectors. However, this response could assist in judging the distance of naturally occurring monocular stimulation.     

Influences of monocular image degradation on the monocular components of fixation disparity

The monocular components of the forced vergence fixation disparity curve were evaluated for equal retinal images and for two kinds of monocular retinal image degradation. Computer-generated nonius lines were used to measure the fixation disparity curve components. Monocular defocus was obtained by placing convex lenses before one eye. In the second instance monocular image degradation was achieved by placing light-scattering filters before one eye. A small percentage of subjects displayed unequal distribution of the monocular components of fixation disparity with no image degradation. For both conditions of monocular image degradation, the distribution of the monocular components was found to be biased in favor of the clear image. However, defocus, which affects the high spatial frequencies relatively more than scatter, was found to have a greater effect on the distribution of the monocular components of fixation disparity than scatter.     

Bayesian combination of ambiguous shape cues

We investigate how different depth cues are combined when one cue is ambiguous. Convex and concave surfaces produce similar texture projections at large viewing distances. Our study considered unambiguous disparity information and its combination with ambiguous texture information. Specifically, we asked whether disparity and texture were processed separately, before linear combination of shape estimates, or jointly, such that disparity disambiguated the texture information. Vertical ridges of various depths were presented stereoscopically. Their texture was consistent (in terms of maximum likelihood) with both a convex and a concave ridge. Disparity was consistent with either a convex or concave ridge. In a separate experiment the stimuli were defined solely by texture (monocular viewing). Under monocular viewing observers consistently reported the convex interpretation of the texture cue. However, in stereoscopic stimuli, texture information modulated shape from disparity in a way inconsistent with simple linear combination. When disparity indicated a concave surface, a texture pattern perceived as highly convex when viewed monocularly caused the stimulus to appear more concave than a "flat" texture pattern. Our data confirm that different cues can disambiguate each other. Data from both experiments are well modeled by a Bayesian approach incorporating a prior for convexity.