在双脉冲光刺激下瞳孔系统的采样控制特性

本文用实验揭示了瞳孔对光动态反应具有采样控制特性。实验中采用各种不同时间间隔的双脉冲光,以开环的方式(Maxwellian View)刺激瞳孔,当双脉冲之间间隔较长时,瞳孔反应相当于对双脉冲光的两次脉冲分别产生瞬态收缩;当双脉冲时间间隔短于0.6s 时,其反应就成了一次瞬态收缩,与单个光脉冲所引起的瞳孔反应一样。同—受试者的多次实验结果相同,不同受试者所得结果也基本一致。故瞳孔对脉冲刺激光引起反应后,必须至少约隔0.6s 才能对另一次脉冲光产生反应,这就说明了瞳孔动态反应具有离散的采样控制特性。实验还进一步证明,瞳孔系统的控制机制是双重模式的控制:不同的刺激条件下,瞳孔反应可呈现为瞬态反应(AC)或持续反应(DC),瞬态反应的 AC 通道为离散的采样控制,持续反应的 DC 通道为连续控制。     

用于研究快速扫视对瞳孔光反射调制作用的新方法

瞳孔对光反射系统和快速扫视系统在解剖学和功能上都有着紧密的联系,但是快速扫视系统对瞳孔的光反射系统是否有调制作用尚无报道。研究这两个系统间的调制作用,必须了解光刺激不均匀和近反应对瞳孔直径变化是否有影响。该研究以人为被试,设计了一种全新的实验方法,研究光刺激不均匀和近反应对瞳孔直径变化的影响。实验方法：将被试的一只眼用密闭的眼罩罩住给予脉冲光刺激,刺激由位于眼罩内全视野范围水平排列的一排发光二极管(light emitting diodes,LEDs)给出,被试的另一只眼用来记录眼动和瞳孔直径的变化,研究水平方向的快速扫视对瞳孔对光反射时瞳孔直径变化的影响。实验结果：比较被试注视视野内不同位置的瞳孔对光反射相对收缩率无显著差异（P=0.148, 非配对样本t检验）。结论：本方法消除了光刺激不均匀和近反应对瞳孔直径变化的影响,可用于研究快速扫视系统对瞳孔光反射系统间的调制作用。     

视觉图形诱发的瞳孔反应

以图形变化刺激进行瞳孔反应研究,实验表明：（１）空间平均亮度守恒的光栅或棋盘格图形翻转能激发起瞳孔反应,为瞬态收缩波形,与ｐｕｐｉｌｌａｒｙ ｅｓｃａｐｅ相似;（２）光栅或棋盘格的空间频率的变化也能引起瞳孔反应,且反应幅度随空间频率差别增大而变大;（３）从均匀亮背景变化到棋盘格图形或者从棋盘格图形变化到黑暗背景,虽然不存在任何局部亮度增强,皆能引起瞳孔反应。实验结果明确证明了人的瞳孔反应系统除接收     

瞳孔光反应系统的空间分布式神经网络模型

为模拟刺激光空间分布变化引起瞳孔反应的实验现象,本文建立了空间分布式神经网络瞳孔模型。它是在瞳孔双通道模型基础上,借鉴Ｃａｎｎｏｎ－Ｒｏｂｉｎｓｏｎ的Ｏｃｕｌｏｍｏｔｏｒ模型的双层网络结构和视网膜的镶嵌式特点,经空间延括而成。空间各部位信号经第一层神经元处理得到对应各部位的线性ＤＣ和非线性ＡＣ输出,在第二层神经元进行空间综合,再经第三层神经元复合去控制效应器官虹膜肌的反应。该分布式部位机制模型能解释多种瞳孔实验现象。     

瞳孔控制系统非线性的频率特性与固有频率

本文用实验方法从时域和频域上揭示了瞳孔对光反应的非线性特性.在亮度以正弦变化的光刺激下,瞳孔反应波形呈同步倍频现象;描述函数的频率-振幅特性曲线呈多峰的锯齿形;具有1.2Hz左右的系统固有频率和极限环现象.     

光点位移运动激发的瞬态瞳孔反应

用等高度的光点位移运动作为刺激来测量瞳孔反应,实验记录表明,即使输入到视网膜的总光通量不变,仅仅是刺激点的位置改变就能激发起瞳孔反应,且其反应的位置分辨率可达１０’,这一实检结果揭示了瞳孔对光反射通路不仅传递了进入瞳孔的总光通量的信息,而且还检测了刺激光点位置变化的信息。     

吗啡对猕猴瞳孔光反应能力的影响

光照能明显改变正常人和动物瞳孔的大小,而精神疾病及药物滥用则影响人和动物瞳孔对光的反应性.因此,瞳孔对光反应异常可以用作检测精神疾病和药物滥用的指标.有关药物滥用是如何影响瞳孔对光的反应性的研究还很少.为定量地测量成瘾性药物对瞳孔光反应变化的影响,该文采用猕猴为实验对象,通过在黑暗环境中测量猕猴在吗啡给予前和吗啡给予后的不同时间段,其瞳孔直径大小以及其对光反应能力的变化情况,来系统研究吗啡是如何影响这种非自主性反射系统的.研究发现,吗啡给予降低了猕猴在黑暗环境中的扩瞳反应,并且降低了瞳孔对光反应的收缩率.该文为将瞳孔对光反应特征用作鉴定吸毒者的检测手段提供了实验依据.     

不同运动图象同时刺激左右眼时的交替视动震颤(OKN)现象

采用了同时对左右眼分别以不同的运动图象刺激的实验方法,来测量及分析其OKN眼动反应,探索在OKN反映中两眼之间的输入关系以及眼动控制机制。实验结果发现在两眼的刺激图象不一致时,眼动反应为交替的OKN反应,即中枢神经系统根据各眼的刺激速度,交替地控制产生OKN眼动反应。本文还从闭环控制上讨论了视网膜上速度误差信号的作用。     

不同运动图象同时刺激左右眼时的交替视动震颤(OKN)现象

采用了同时对左右眼分别以不同的运动图象刺激的实验方法,来测量及分析其OKN眼动反应,探索在OKN反映中两眼之间的输入关系以及眼动控制机制。实验结果发现在两眼的刺激图象不一致时,眼动反应为交替的OKN反应,即中枢神经系统根据各眼的刺激速度,交替地控制产生OKN眼动反应。本文还从闭环控制上讨论了视网膜上速度误差信号的作用。     

柑橘细胞电融合参数选择及种间体细胞杂种植株再生

以“Ｐａｇｅ”橘柚（ＣｉｔｒｕｓｒｅｔｉｃｕｌａｔａＢｌａｎｃｏ×Ｃ．ｐａｒａｄｉｓｉＭａｃｆ）胚性悬浮系原生质体和粗柠檬（Ｃ．ｊａｍｂｈｉｒｉＬｕｓｈ）叶肉原生质体为融合试材,摸索了适合柑橘的电融合参数。研究表明,在ＡＣ（交变电场）１２５Ｖ／ｃｍ、ＤＣ（直流脉冲）１２５０Ｖ／ｃｍ、ＡＣ作用时间６０ｓ、ＤＣ脉冲时间５０μｓ、ＤＣ脉冲个数为３、ＤＣ脉冲间隔为０．５ｓ时融合率较高,双核异核体率可以达到１５％以上。利用不同类型原生质体比重的不同,融合后通过控制离心时间,可以收集到更高比例的双核异核体。融合产物经培养,３～４个月再生小植株。染色体计数结合形态学观察表明,再生的１５０株小植株中７８％为四倍体,其余为二倍体叶肉亲本再生类型。再生植株经过氧化物酶同工酶及ＲＡＰＤ分析,表明得到了体细胞杂种,还证明获得了１株叶肉亲本同源四倍体再生类型。     

The Pupillary Light Response Reveals the Focus of Covert Visual Attention

The pupillary light response is often assumed to be a reflex that is not susceptible to cognitive influences. In line with recent converging evidence, we show that this reflexive view is incomplete, and that the pupillary light response is modulated by covert visual attention: Covertly attending to a bright area causes a pupillary constriction, relative to attending to a dark area under identical visual input. This attention-related modulation of the pupillary light response predicts cuing effects in behavior, and can be used as an index of how strongly participants attend to a particular location. Therefore, we suggest that pupil size may offer a new way to continuously track the focus of covert visual attention, without requiring a manual response from the participant. The theoretical implication of this finding is that the pupillary light response is neither fully reflexive, nor under complete voluntary control, but is instead best characterized as a stereotyped response to a voluntarily selected target. In this sense, the pupillary light response is similar to saccadic and smooth pursuit eye movements. Together, eye movements and the pupillary light response maximize visual acuity, stabilize visual input, and selectively filter visual information as it enters the eye.     

Visual pigment processes and prolonged pupillary responses in insect photoreceptor cells

The visual pigment in the peripheral retinular cells of the hoverfly Syrphus balteatus was investigated by absorbance difference measurements. Different visual pigments were found in the dorsal versus the ventral part of the eye in the male, but not in the female. In the male in the dorsal part of the eye the visual pigment has an isosbestic point at 513 nm; in the ventral part this value is 490 nm. The latter value is found in the female in both parts of the eye.Prolonged pupillary responses were studied in the male Syrphus and appeared to be most marked in the ventral part of the eye. In both hoverfly and blowfly prolonged pupillary responses are induced by short wavelength light only; i.e., by light which excessively can convert rhodopsin into metarhodopsin. By contrast, in butterflies red light (and a long dark adaptation time) is necessary to evoke a prolonged pupillary response. It was demonstrated in both hoverfly and blowfly that long wavelength light, which reconverts metarhodopsin into rhodopsin, inhibits a prolonged pupillary response; or, accelerates pupil opening.Based on material presented at the European Neurosciences Meeting, Florence, September 1978     

Investigations of pigment granule transport systems in Gonodactylus oerstedii (Crustacea: Hoplocarida: Stomatopoda)

Compound eyes of the stomatopod, Gonodactylus oerstedii, exhibit pupillary reflection responses which arise from migration of retinular cell pigment granules. In the light, reflectance from the eye increases as pigment granules accumulate around light-sensitive rhabdoms and scatter incoming light back out of the eye (pupillary closure). At dark onset, reflectance diminishes as pigment granules disperse centrifugally, enhancing photon capture by the rhabdom. We investigated the mechanisms of the pupillary response in intact animals by measuring reflectance from the eye under different temperature conditions. Lowering the temperature from 27° to 7 °C caused an increase in reflectance of infrared light in the absence of visible-light stimuli, indicating pupillary closure. When given light stimuli as temperature decreased, the eye continued to produce reflection increases which decreased in amplitude as the between stimulus reflectance level increased. All low-temperature effects were reversed when temperature was increased to normal. The rate of pupillary closure was insensitive to temperature, with a temperature quotient (Q₁₀) of 0.8 ± 0.1 s.e.m, while pupillary opening was extremely temperature sensitive (Q₁₀ of 5.4 ± 0.4). Different temperature sensitivities for pupillary opening and closing suggest that these processes involve different mechanisms.Abbreviations IOP intracelllular optical physiology - Q₁₀ temperature quotient     

THE EFFECTS OF LIGHT ON THE DEVELOPMENT OF THE CELLULAR SLIME MOLD ACRASIS ROSEA

No fruiting of the NC-18 isolate of Acrasis rosea occurs in cultures maintained in continuous light or in continuous dark. The use of different food organisms does not alter the aforementioned behavior. The time at which fruiting occurs in this isolate can be regulated by administering stimulatory light followed by a dark period. Mature sorocarps are formed approximately 14 hr after the termination of light and the start of darkness. Within this 14-hr interval aggregation and sorocarp development occur. After about 6 hr of dark incubation, NC-18 amebae, previously stimulated by light, form a few weak aggregation centers. After 8 hr of dark incubation there are numerous aggregation areas, large in size and deep rose in color. By 10 hr the aggregations are quite compact and firm in appearance, and between 12 and 14 hr late aggregations, sorogens and, finally, mature sorocarps are formed. The minimum dark period, i.e., the minimum time that is required in darkness (for cultures previously stimulated with light) to obtain at least some fruiting within the 14-hr developmental period, is 7–8 hr for NC-18 and 5–6 hr for Tu-26. Maximum numbers of sorocarps form when cultures are given 10–11 hr of uninterrupted dark. Light-stimulated cultures of NC-18 placed in darkness and interrupted by a 10- or 30-min exposure to wide-spectrum blue or cool white fluorescent light an hour prior to the minimal dark period exhibit a 4–5 hr-delay in fruiting when returned to darkness and inspected at intervals following the second irradiation. Growth and fruiting of NC-18 occurred with purified food sources of each of five different species of Chlorella and with the alga Stichococcus bacillaris. This is apparently the first report of the utilization of algae as food sources by a cellular slime mold. Fruiting of NC-18 was readily arrested by lowering the relative humidity to 40–45%. This change in the moisture content of the surrounding air induced microcyst formation. Growth on buffered medium occurred in the entire pH range tested, 3.5–7.6, but fruiting occurred only between pH 5.0 and 6.6.     

Binocular alternating pulse stimuli: Experimental and modeling studies of the pupil reflex to light

In our experiment, alternating pulse stimuli of both low and high intensity are used to study the pupil reflex to light. When applied monocularly, high intensity stimulation normally results in a sustained contraction; when alternated between the two eyes, it is found to produce small transient responses similar to those obtained with low intensity monocular stimulation. In order to study the mechanisms regulating these binocular responses, a model of the pupillary light reflex is constructed. It includes parallel AC and DC pathways for processing the light stimulus to produce motor signals to the iris muscles, nonlinear parameter control of pathway gains dependent upon internal operating level, binocular summation of DC pathway signals to produce that operating level, equal motor responses of both pupils, and iris neuromuscular delays and lags. The model is found to simulate the experimental data. It shows the binocular transient responses to be due to the canceling by summation of the symmetric DC pathway responses to alternating stimuli, thus allowing the AC pathway signals to become manifest. Therefore the dilatory portion of the transient responses is shown to be due to the lead-lag operator in the AC pathway and not to the off-dilatation elicited by removal of the light stimulus from the eye. Finally the results of our study are used to discuss the Marcus Gunn pupillary sign, a clinical test utilizing this binocular alternating pulse stimulation for detecting unilateral afferent defects.     

Binocular coordination of the eyes during reading

Saccadic eye movements and fixations are the behavioral means by which we visually sample text during reading. Human oculomotor control is governed by a complex neurophysiological system involving the brain stem, superior colliculus, and several cortical areas. A very widely held belief among researchers investigating primate vision is that the oculomotor system serves to orient the visual axes of both eyes to fixate the same target point in space. It is argued that such precise positioning of the eyes is necessary to place images on corresponding retinal locations, such that on each fixation a single, nondiplopic, visual representation is perceived. Vision works actively through a continual sampling process involving saccades and fixations. Here we report that during normal reading, the eyes do not always fixate the same letter within a word. We also demonstrate that saccadic targeting is yoked and based on a unified cyclopean percept of a whole word since it is unaffected if different word parts are delivered exclusively to each eye via a dichoptic presentation technique. These two findings together suggest that the visual signal from each eye is fused at a very early stage in the visual pathway, even when the fixation disparity is greater than one character (0.29 deg), and that saccade metrics for each eye are computed on the basis of that fused signal.