蜻蜒运动检测神经元的光谱反应

蜻蜒腹神经束上存在着自运动检测神经元和目标运动检测神经元.我们采用了两种视觉刺激条件来测试自运动检测神经元的光谱反应.当采用控制强度和波长的闪光进行测试时、它们的光谱反应曲线与绿色光感受器的光谱灵敏度曲线极其相似,峰值位于500nm处.然而采用运动的条纹进行测试时,它们的峰值却位于560nm处.当用一种颜色的运动图案作为目标放置在另一种颜色背景的前方测试时,发现存在某个目标的照明强度值能使反应下降到自发放电的水平,这表明自运动检测器无法检测这二种颜色的差别,即它们是色盲的、它主要接受来自绿色光感受器的信号.目标运动检测神经元的光谱反应特性与自运动检测神经元的不同,目标运动检测神经元在以380nm至580nm的范围中有着平坦的光谱反应曲线,有时在紫外频段出现峰有(?)前景与背景颜色不同且固定背景光的颜色与强度而改变前景的光强时,神经元的反应不会下降到自发放电水平,当背景为绿色而目标为另一个颜色.特别是兰色时,神经元反应强烈,但当背景为兰色而目标为绿色时,它们的反应相对较弱.这些结果表明目标运动检测神经元是对颜色敏感的.     

自由飞行蜜蜂跟踪运动目标的研究

本文对自由飞行蜜蜂跟踪运动目标的能力进行了研究.实验结果表明蜜蜂能够准备地跟踪运动目标.当目标的距离较大时蜜蜂主要通过校正与目标的角度偏差接近目标.无论是在水平方向或是垂直方向,密蜂使用了目标误差角以及目标相对蜜蜂的角速度的信息.蜜蜂的运动目标跟踪控制系统,往往把目标置于复眼的前下方体轴夹角约35度的视场区域中.目标与背景颜色对(?)的的实验结果表明蜜蜂跟踪行为所利用的目标的速度的信息是来自于对绿色敏感的光感受器:而与目标位置有关的方位角的信息则不仅仅来自于绿色光感受器,而且也来自于兰色光感受器.当蜜蜂与目标的距离较近时,蜜蜂除了角度校正以外还使用了横向移动来跟踪运动目标.横向目标跟踪系统看来仅仅接受来自于对绿色敏感的光感受器的信号.     

运动结构背景对视觉系统神经元反应的调制作用

对蟾蜍的５６个视顶盖神经元的视觉反应进行了定量考察和分析,发现它们不仅对黑目标起反应,也对结构目标起反应．同相运动的结构背景使５３．５％的神经元的反应完全抑制,而异相运动则只有１０％的神经元完全被抑制,却有２１．６％的神经元反应增强．遮盖感受野（ＲＦ）中心区,则同相运动使某些细胞脱抑制,而异相运动使其抑制强度稍有增强．遮盖ＲＦ的外周区,几乎全部研究过的神经元对结构背景运动本身也起反应。本研究还发现,如果预先将一目标放在兴奋性感受野（ＥＲＦ）中央静止不动,并使结构背景在水平方向匀速移动较长时间后突然停止运动,则被研究过的６６个视盖神经元中有２９个发放一串脉冲,即神经元的运动后放电．各个神经细胞放电的脉冲多寡不一。若在ＥＲＦ中央不放置静止目标,仅是结构背景的水平运动不能诱发放电．此效应的出现,既与目标背景间反差符号（即目标为白色或黑色）无关,也与背景的运动方向无关。为诱发这一效应,不仅要求背景运动时间较长（至少在２０秒以上）,而且目标的面积要有足够大。     

伤害性刺激和电针对大鼠中缝大核内缝-脊神经元的效应

用玻璃微电极细胞外记录大鼠中缝大核神经元放电,刺激脊髓胸段背外侧部诱发逆行动作电位,根据其潜伏期恒定性,能跟随高频刺激以及可与自发放电碰撞而消失等标准来鉴定缝-脊神经元。共记录45个缝-脊神经元,其传导速度多在15—60m/s 范围。对伤害性刺激发生兴奋性(增频)反应的31个,抑制性(减频)反应的6个。两个类型神经元的自发放电频率分别为5.74±0.96Hz 和12.03±2.68Hz。另有3个为兴奋抑制转化型,反应的转化与背景自发放电水平有关,即放电频率低时,对伤害性刺激为兴奋性反应,而当自发放电频率增高时,则转化为抑制性反应。此外还有5个神经元对伤害性刺激无明显反应。电针“足三里”对兴奋型的缝-脊神经元(n=13)能明显激活并抑制其伤害性反应,后者可能是由于下行抑制而产生的继发性效应。     

刺激大鼠杏仁外侧核对皮层A Ⅰ区ON-OFF神经元反应及调谐曲线的影响

在30只氨基甲酸乙酯麻醉的SD大鼠上记录神经元单位放电,观察短纯音诱发的皮层A Ⅰ区神经元ON-OFF反应的特性及电刺激杏仁外侧核(lateral amygdaloid nucleus,LA)对ON-OFF反应以及调谐曲线的影响.实验证实,A Ⅰ区神经元ON-OFF反应的模式与纯音刺激的强度、频率及作用时程有关;刺激LA可以抑制ON-OFF反应的放电频数,使反应的阈值升高,或使反应放电构型发生变化;此外,刺激LA能使ON-OFF神经元的调谐曲线变窄,Q10数值增大.研究结果不仅表明ON-OFF神经元能对纯音刺激的时程、强度和频率等多种信息进行编码,而且还证明杏仁外侧核可以在皮层水平参与听觉信息的调制,削弱或衰减某些听觉信息,导致整个调谐曲线上移变窄,从而提高A Ⅰ区ON-OFF神经元的频率选择性能,有利于检测外界嘈杂环境中特定的听觉信息.     

乙酰胆碱对青蛙松果体中光敏神经节细胞自发放电的影响

本实验应用微量离子电泳技术,研究了乙酰胆碱对明或暗适应状态青蛙(Rana esculenta)松果体无色感或光敏神经元(Achromatic or Lumninance neuron)自发放电的影响.在所检测过的124个神经元中,乙酶胆碱导致其自发放电频率显著上升的大约占82%,另外有2%的神经元对乙酰胆碱的反应为抑制性,其余的16%无反应.乙酰胆碱引起的这种兴奋性反应具有剂量相关性,可逆性和重复性.     

左旋千金藤啶碱的非经典安定剂特性——电生理和行为的研究

在记录神经元放电频率的实验中,发现麻醉或麻痹大鼠给予DA受体拮抗剂SPD,使VTA,SNC和DA神经元放电频率增加.但随着剂量的增加,SPD选择性地使VTA的DA神经元放电完全抑制,可被DA受体激动剂APO所翻转.提示这种抑制作用可能是DI.但SPD不抑制SNCDA神经元放电.在计数自发放电的神经元数目的实验中,观察到:慢性给予SPD21d后,大鼠VTA部位自发放电的DA神经元数目减少,有量效关系.可被APO所翻转.相反,同样给药并不影响SNC部位自发放电的DA神经元数目.当急性给予SPD时,VTA自发放电的DA神经元数目也减少,而SNC自发放电的DA细胞数不受影响.在行为实验中,SPD能抑制APO引起的定型活动,但SPD本身引起的僵住症很弱,仅能维持15min,并且无剂量依赖关系.上述结果提示:SPD选择性抑制VTADA神经元,而对SNCDA神经元的抑制作用很弱,引起的锥体外系副作用弱,可能发展成为新一代的非经典安定剂.     

乙酰胆碱对离体大鼠延髓头端腹外侧区神经元自发放电的影响

在８９张Ｓｐｒａｇｕｅ－Ｄａｗｌｅｙ大鼠延髓脑片,用玻璃微电极记录到１６５个延髓头端腹外侧区神经元的自发放电,其放电形式有三种：规则型;不规则型,静息型,乙酰胆碱对自发放电有兴奋,抑制双相和无影响四种效应,各占所测试神经元数的４１．８％,２０％,３％和自发放电有兴奋,抑制双相和无双相和影响四种效应,各占所有测试神经元数的４１．８％,２０％,３Ｔ和３５．２％。     

受损背根节神经元对四乙基胺反应的敏感性与其放电型式的关系

为了研究受损背根节神经元的放电型式与其对钾离子通道阻断剂四乙基胺（ｔｅｔｒａｅｔｈｙｌａｍｍｏｎｉｕｍ,ＴＥＡ）反应敏感性的关系,在大鼠背根节慢性压迫模型上记录单纤维自发放电。这些自发放电有周期和非周期两种型式,ＴＥＡ（２ｍｍｏｌ／Ｌ）分别引起２７．３％的周期放电神经元和９３．２％的非周期放电神经元 放电增加（Ｐ〈０．０１）。非周期放电神经元对不同浓度的ＴＥＡ的反应均比周期放电神经元大（Ｐ〈０．０     

电刺激大鼠脚内核对脚桥核神经元放电的影响

目的:观察电刺激大鼠脚内核(EP)对大鼠脚桥核(PPN)神经元自发放电的影响,进一步探讨脑内电刺激治疗帕金森病(PD)的机制。方法:应用细胞外记录的方法观察不同频率电刺激(强度0.6 mA,波宽0.06 ms,时程5 s,频率5 Hz、10Hz、20Hz、50Hz、100Hz、150Hz、200Hz)大鼠EP对PPN神经元放电的影响。结果:实验记录了大鼠33个神经元的自发放电,其放电频率在3.6~52.2Hz之间,平均为(15.95±8.56)Hz;当刺激频率为100Hz时,抑制效应最显著(P<0.05)。结论:高频电刺激大鼠EP对PPN神经元自发放电的影响主要为抑制作用,提示高频刺激EP可通过抑制PPN神经元活动参与PD的治疗。     

Acoustic facilitation of object movement detection during self-motion

In humans, as well as most animal species, perception of object motion is critical to successful interaction with the surrounding environment. Yet, as the observer also moves, the retinal projections of the various motion components add to each other and extracting accurate object motion becomes computationally challenging. Recent psychophysical studies have demonstrated that observers use a flow-parsing mechanism to estimate and subtract self-motion from the optic flow field. We investigated whether concurrent acoustic cues for motion can facilitate visual flow parsing, thereby enhancing the detection of moving objects during simulated self-motion. Participants identified an object (the target) that moved either forward or backward within a visual scene containing nine identical textured objects simulating forward observer translation. We found that spatially co-localized, directionally congruent, moving auditory stimuli enhanced object motion detection. Interestingly, subjects who performed poorly on the visual-only task benefited more from the addition of moving auditory stimuli. When auditory stimuli were not co-localized to the visual target, improvements in detection rates were weak. Taken together, these results suggest that parsing object motion from self-motion-induced optic flow can operate on multisensory object representations.     

Disruptive Colouration and Perceptual Grouping

Camouflage is the primary defence of many animals and includes multiple strategies that interfere with figure-ground segmentation and object recognition. While matching background colours and textures is widespread and conceptually straightforward, less well explored are the optical ‘tricks’, collectively called disruptive colouration, that exploit perceptual grouping mechanisms. Adjacent high contrast colours create false edges, but this is not sufficient for an object’s shape to be broken up; some colours must blend with the background. We test the novel hypothesis that this will be particularly effective when the colour patches on the animal appear to belong to, not merely different background colours, but different background objects. We used computer-based experiments where human participants had to find cryptic targets on artificial backgrounds. Creating what appeared to be bi-coloured foreground objects on bi-coloured backgrounds, we generated colour boundaries that had identical local contrast but either lay within or between (illusory) objects. As predicted, error rates for targets matching what appeared to be different background objects were higher than for targets which had otherwise identical local contrast to the background but appeared to belong to single background objects. This provides evidence for disruptive colouration interfering with higher-level feature integration in addition to previously demonstrated low-level effects involving contour detection. In addition, detection was impeded in treatments where targets were on or in close proximity to multiple background colour or tone boundaries. This is consistent with other studies which show a deleterious influence of visual ‘clutter’ or background complexity on search.     

Simulated self-motion alters perceived time to collision

Many authors have assumed that motor actions required for collision avoidance and for collision achievement (for example, in driving a car or hitting a ball) are guided by monitoring the time to collision (TTC), and that this is done on the basis of moment-to-moment values of the optical variable tau [1] [2] [3]. This assumption has also motivated the search for single neurons that fire when tau is a certain value [4] [5] [6] [7] [8]. Almost all of the laboratory studies and all the animal experiments were restricted to the case of stationary observer and moving object. On the face of it, this would seem reasonable. Even though humans and other animals routinely perform visually guided actions that require the TTC of an approaching object to be estimated while the observer is moving, tau provides an accurate estimate of TTC regardless of whether the approach is produced by self-motion, object-motion or a combination of both. One might therefore expect that judgements of TTC would be independent of self-motion. We report here, however, that simulated selfmotion using a peripheral flow field substantially altered estimates of TTC for an approaching object, even though the peripheral flow field did not affect the value of tau for the approaching object. This finding points to long range interactions between collision-sensitive visual neurons and neural mechanisms for processing self-motion.     

How Moving Backgrounds Influence Interception

Reaching movements towards an object are continuously guided by visual information about the target and the arm. Such guidance increases precision and allows one to adjust the movement if the target unexpectedly moves. On-going arm movements are also influenced by motion in the surrounding. Fast responses to motion in the surrounding could help cope with moving obstacles and with the consequences of changes in one’s eye orientation and vantage point. To further evaluate how motion in the surrounding influences interceptive movements we asked subjects to tap a moving target when it reached a second, static target. We varied the direction and location of motion in the surrounding, as well as details of the stimuli that are known to influence eye movements. Subjects were most sensitive to motion in the background when such motion was near the targets. Whether or not the eyes were moving, and the direction of the background motion in relation to the direction in which the eyes were moving, had very little influence on the response to the background motion. We conclude that the responses to background motion are driven by motion near the target rather than by a global analysis of the optic flow and its relation with other information about self-motion.     

How Bees Discriminate a Pattern of Two Colours from Its Mirror Image

A century ago, in his study of colour vision in the honeybee (Apis mellifera), Karl von Frisch showed that bees distinguish between a disc that is half yellow, half blue, and a mirror image of the same. Although his inference of colour vision in this example has been accepted, some discrepancies have prompted a new investigation of the detection of polarity in coloured patterns. In new experiments, bees restricted to their blue and green receptors by exclusion of ultraviolet could learn patterns of this type if they displayed a difference in green contrast between the two colours. Patterns with no green contrast required an additional vertical black line as a landmark. Tests of the trained bees revealed that they had learned two inputs; a measure and the retinotopic position of blue with large field tonic detectors, and the measure and position of a vertical edge or line with small-field phasic green detectors. The angle between these two was measured. This simple combination was detected wherever it occurred in many patterns, fitting the definition of an algorithm, which is defined as a method of processing data. As long as they excited blue receptors, colours could be any colour to human eyes, even white. The blue area cue could be separated from the green receptor modulation by as much as 50°. When some blue content was not available, the bees learned two measures of the modulation of the green receptors at widely separated vertical edges, and the angle between them. There was no evidence that the bees reconstructed the lay-out of the pattern or detected a tonic input to the green receptors.     

Fruit Colour Preferences of Redwings (Turdus iliacus): Experiments with Hand-Raised Juveniles and Wild-Caught Adults

Certain fruit colours and their contrast with the background coloration are suggested to attract frugivorous birds. To test the attractiveness of different colours, we performed three experiments in laboratory with controlled light conditions. In the first two experiments, we studied the fruit colour preferences of naive juvenile redwings. In the third experiment, we continued to investigate whether the contrast of the fruit colour with the background coloration affects the preference of both naive juveniles and experienced adult redwings. In the first experiment, juvenile birds preferred black, UV‐blue and red berries, to white ones. In pairwise trials, a new set of juveniles still preferred red berries to white ones. When testing the effect of contrasts on their choice, juveniles preferred UV‐blue berries to red ones on a UV‐blue background. However, no preference was found, when the background was either red or green. Adult redwings preferred UV‐blue berries to red ones on all backgrounds. According to these results, juveniles seem to have an innate avoidance of white berries. Furthermore, the foraging decisions of fruit‐eating birds are affected more by fruit colour than its contrast with background coloration, at least when contrasting displays are encountered from relatively short distances. Differences in preferences of adult and juvenile birds also indicate that learning seems to play a role in fruit choices.     

Zum Farbsehvermögen von Hausziegen (Capra hircus L.)

Tests on male goats were designed to determine their capacity for colour vision. The colours yellow, orange, blue, violet and green were tested against gray nuances of like brightness. Goats were found to be able to distinguish between colours and gray nuances. The rate of errors increased in the order: orange, green, red, yellow, violet, blue.     

Influence of Visual Motion,Suggestion, and Illusory Motion on Self-Motion Perception in the Horizontal Plane

A moving visual field can induce the feeling of self-motion or vection. Illusory motion from static repeated asymmetric patterns creates a compelling visual motion stimulus, but it is unclear if such illusory motion can induce a feeling of self-motion or alter self-motion perception. In these experiments, human subjects reported the perceived direction of self-motion for sway translation and yaw rotation at the end of a period of viewing set visual stimuli coordinated with varying inertial stimuli. This tested the hypothesis that illusory visual motion would influence self-motion perception in the horizontal plane. Trials were arranged into 5 blocks based on stimulus type: moving star field with yaw rotation, moving star field with sway translation, illusory motion with yaw, illusory motion with sway, and static arrows with sway. Static arrows were used to evaluate the effect of cognitive suggestion on self-motion perception. Each trial had a control condition; the illusory motion controls were altered versions of the experimental image, which removed the illusory motion effect. For the moving visual stimulus, controls were carried out in a dark room. With the arrow visual stimulus, controls were a gray screen. In blocks containing a visual stimulus there was an 8s viewing interval with the inertial stimulus occurring over the final 1s. This allowed measurement of the visual illusion perception using objective methods. When no visual stimulus was present, only the 1s motion stimulus was presented. Eight women and five men (mean age 37) participated. To assess for a shift in self-motion perception, the effect of each visual stimulus on the self-motion stimulus (cm/s) at which subjects were equally likely to report motion in either direction was measured. Significant effects were seen for moving star fields for both translation (p = 0.001) and rotation (p<0.001), and arrows (p = 0.02). For the visual motion stimuli, inertial motion perception was shifted in the direction consistent with the visual stimulus. Arrows had a small effect on self-motion perception driven by a minority of subjects. There was no significant effect of illusory motion on self-motion perception for either translation or rotation (p>0.1 for both). Thus, although a true moving visual field can induce self-motion, results of this study show that illusory motion does not.     

Stereo vision and isoluminance.

Recent experiments have shown that stereo depth is given by fusion of illusory ('cognitive') contours. They occur across quite large gaps in figures, when these gaps are unlikely and form the shape of a probable (nearer) masking object or masking feature. Implications are that: (a) clearly defined contours and regions of brightness difference can be produced as postulates from sensory evidence, which may be surprising absence of stimulation; (b) each eye-system can derive its own postulates, or hypotheses, which (c) can be combined to give stereo vision. It has been shown that random-dot stereo depth does not occur when there is colour contrast but no brightness difference between the dots and their background. This we have confirmed by using a new technique for producing isoluminant pictures, of any complexity, with exact registration for any two colours. With this technique, we find large displacements of narrow borders bounding regions that are shifted across isoluminance. These displacements, which are clearly seen as movements, occur with or without colour differences. The direction of shift depends on whether the narrow border is light or dark. It is found that these dramatic shifts do not - when produced in opposite directions to the two eyes and fused - produce stereo depth. It is concluded, following Julesz's paradigm, that these contour displacements have their neural orgin not retinally, but after stereo fusion. Experiments combining the 'cognitive contours' stereo depth with isoluminance are described.     

Learning and discrimination of coloured papers in the walking blowfly,Lucilia cuprina

Summary A new training and testing paradigm for walking sheep blowflies, Lucilia cuprina, is described. A fly is trained by presenting it with a droplet of sugar solution on a patch of coloured paper. After having consumed the sugar droplet, the fly starts a systematic search. While searching, it is confronted with an array of colour marks consisting of four colours displayed on the test cardboard (Fig. 1). Colours used for training and test include blue, green, yellow, orange, red, white and black.Before training, naive flies are tested for their spontaneous colour preferences on the test array. Yellow is visited most frequently, green least frequently (Table 2). Spontaneous colour preferences do not simply depend on subjective brightness (Table 1).The flies trained to one of the colours prefer this colour significantly (Figs. 5 and 9–11). This behaviour reflects true learning rather than sensitisation (Figs. 6–7). The blue and yellow marks are learned easily and discriminated well (Figs. 5, 9, 11). White is also discriminated well, although the response frequencies are lower than to blue and yellow (Fig. 11). Green is discriminated from blue but weakly from yellow and orange (Figs. 5, 9, 10). Red is a stimulus as weak as black (Figs. 8, 9). These features of colour discrimination reflect the spectral loci of colours in the colour triangle (Fig. 14).The coloured papers seem to be discriminated mainly by the hue of colours (Fig. 12), but brightness may also be used to discriminate colour stimuli (Fig. 13).