老年猫视皮层细胞对刺激反应的对比敏感度下降伴随皮层内抑制作用减弱(英文)

对人类和动物的心理学研究证实,老年个体的视觉对比敏感度相对青年个体显著下降。为揭示其可能的神经机制,采用在体细胞外单细胞记录技术研究青、老年猫(Felis catus)初级视皮层(primary visual cortex,V1)细胞对不同视觉刺激对比度的调谐反应。结果显示,老年猫V1细胞对视觉刺激反应的平均对比敏感度比青年猫显著下降,这与灵长类报道的研究结果相一致,表明衰老影响视皮层细胞对视觉刺激反应的对比敏感度是灵长类和非灵长类哺乳动物中普遍存在的现象,并可能是介导老年性视觉对比敏感度下降的神经基础。另外,与青年猫相比,老年猫初级视皮层细胞对视觉刺激的反应性显著增强,信噪比下降,感受野显著增大,表明衰老导致的初级视皮层细胞对视觉刺激反应的对比敏感度下降伴随着皮层内抑制性作用减弱。     

视觉剥夺猫外膝体神经元最优方位的分布特性

记录和测定了视觉剥夺猫（ｄａｒｋ－ｒｅａｒｅｄｃａｔｓ）外膝体３４４个细胞的方位调谐等感受野特性,多数细胞（８２％）具有方位敏感性（Ｂｉａｓ＞０．１）。最优方位的分布与正常猫类似,偏向于水平方位,但分布特性强于正常猫。与正常猫类似,视觉剥夺猫外膝体细胞的最优方位与该细胞感受野在视网膜上的位置有关,偏向平行于视网膜中心区与感受野中心的连线（向心线）;外膝体内位置相邻近的细胞具有相近的最优方位,亦呈现初步有序排列。结果表明：外膝体细胞最优方位的分布特性与后天视觉经验无关而可能来源于遗传因素。     

基于敏感度-主观偏好矩阵的哈尼梯田视觉景观关键区识别

以哈尼梯田遗产核心区主要视觉景观为研究对象,应用GIS技术选取相对坡度、相对距离和出现几率3个客观因子进行景观视觉敏感度分析,运用美景度评价法得到50名专业人士的主观偏好,综合景观视觉敏感度和主观偏好评分,构建敏感度-主观偏好矩阵,将哈尼梯田遗产核心区视觉景观划分为四个区域并提出相应的景观保护、规划建议。结果表明:老虎嘴、麻栗寨茶厂位于敏感度、偏好评价双高的\"视觉景观关键区\",多依树属于偏好评价高、敏感度低的\"自然发展区\",黄草岭是敏感度高、偏好评价低的\"优先改进区\",坝达、箐口、全福庄是敏感度、偏好评价双低的\"次优先改进区\"。通过构建矩阵结合主客观两方面的评价结果,GIS有效量化抽象的数据,偏好评价真实反映观景者内心感知,为当下的景观视觉评价提供思路。     

猫对方位辨别的知觉学习

观察了猫对光栅方位辨别的知觉学习。两只成年猫(cat1和cat2)先单眼辨别方位差为30度角的两个正弦光栅以获得食物奖赏。当辨别正确率达80%以上后,猫开始学习用单眼辨别夹角连续变化的两个正弦光栅,采用二进一递进训练方法(two-correct down/one-error up staircase method,即猫连续两次辨别正确,则待辨别的两个光栅的方位差降低为原来的0.9倍;如果辨别错误一次,则方位差增加至原来的1.1倍)追踪猫可辨别的光栅方位差。在训练前后分别检测训练眼和非训练眼对不同方位差(2°,4°,6°,8°,10°,12°,16°,20°,24°,30°)光栅辨别的正确率。结果显示:对于固定方位差光栅的辨别学习,学习效果能完全传递给非训练眼;但对方位差连续减小的光栅辨别,两眼间几乎没有传递。提示固定方位角和连续变化方位角光栅的辨别学习可能由不同的信息处理机制介导。     

用显示器测量办公亮度环境下的人眼对比度敏感视觉特性

对比度敏感是描述人眼视觉系统空间特性的主要指标之一,对比度敏感函数是反映不同条件下的对比度敏感与空间频率之间的关系。人眼对比度敏感数据的测量受到环境亮度较大的影响,为了研究常用办公环境条件下的人眼对比度敏感情况,对6位青年在环境亮度分别为153,312,470 cd/m2和暗室条件下,在距离为2米处观测11种空间频率的矩形光栅进行测量,光栅用显示器进行显示,其平均亮度分别为60和90 cd/m2。实验结果表明,对于相同频率的光栅,人眼对比度敏感程度随着环境亮度的增加而减小,而且人眼在暗室环境下比在办公环境条件下对亮度光栅更敏感;但是在观测平均亮度为60cd/m2的光栅时,人眼特殊地对在环境亮度为312 cd/m2的条件下更敏感。     

用显示器测量办公亮度环境下的人眼对比度敏感视觉特性

对比度敏感是描述人眼视觉系统空间特性的主要指标之一,对比度敏感函数是反映不同条件下的对比度敏感与空间频率之间的关系。人眼对比度敏感数据的测量受到环境亮度较大的影响,为了研究常用办公环境条件下的人眼对比度敏感情况,对6位青年在环境亮度分别为153,312,470 cd/m2和暗室条件下,在距离为2米处观测11种空间频率的矩形光栅进行测量,光栅用显示器进行显示,其平均亮度分别为60和90 cd/m2。实验结果表明,对于相同频率的光栅,人眼对比度敏感程度随着环境亮度的增加而减小,而且人眼在暗室环境下比在办公环境条件下对亮度光栅更敏感;但是在观测平均亮度为60cd/m2的光栅时,人眼特殊地对在环境亮度为312 cd/m2的条件下更敏感。     

猫上丘视觉神经元的取向和方向选择性

基于对上丘细胞对运动光棒刺激反应特性的定量分析,首次明确提出猫上丘视觉神经元具有一定的取向选择性,并从形态基础和生理功能的角度讨论了这种选择性存在的意义。另外还发现上丘的方向和取向选择性均弱于初级视皮层,且对向视野上、下方运动的光棒较为敏感。     

双眼和单眼视觉剥夺猫外膝体细胞的图形适应

为测定丘脑外膝体细胞的图形适应是否依赖于早期视觉经验,在细胞外记录了双眼和单眼缝合的猫外膝体中断细胞对手工时间运动光栅刺激的反应。在双眼剥夺猫,占６８％的记录到的细胞在３０ｓ内反应下降到稳定值,其平均反应值下降３３％,适应程度较正常猫显著。在单眼剥夺猫,记录到的剥夺眼驱动的和非剥夺眼驱动的细胞中,分别有占５３％和４４％的细胞显示图形适应,两者差别不大。研究表明,早期视剥夺能增强或保持图形适应,提示     

猫外膝体神经元非寻常的方位调谐特性──Ⅱ．在去视皮层猫和视觉剥夺猫（Dark－reared cats）的研究

以移动的正弦光栅作为刺激,用玻璃微电极记录以冰冻法毁损皮层１７、１８、１９区和外侧上雪氏回区后的猫外膝体的单细胞反应,测定了５７９个细胞的方位调谐特性,另外还在视觉剥夺猫外膝体测定了３４４个细胞的方位调谐特性,与正常猫相似,去视以猫和视觉剥夺猫外膝体的少数细胞具有非寻常的方位调谐特性,包括具蝴蝶形调谐曲线的方位调谐特性、双调谐的方位调谐特性和最优方位随刺激空间的不同而变化的方位调谐特性。结果表明外     

猫外膝体神经元非寻常的方位调谐特性──Ⅱ．在去视皮层猫和视觉剥夺猫（Dark－reared cats）的研究

以移动的正弦光栅作为刺激,用玻璃微电极记录以冰冻法毁损皮层１７、１８、１９区和外侧上雪氏回（ＬＳ）区后的猫外膝体的单细胞反应,测定了了５７９个细胞的方位调谐特性．另外还在视觉剥夺猫外膝体测定了３４４个细胞的方位调谐特性．与正常猫相似,去视皮层猫和视觉剥夺猫外膝体的少数细胞（约占１０％）具有非寻常的方位调谐特性,包括具蝴蝶形调谐曲线的方位调谐特性、双调谐（Ｂｉｍｏｄａｌ）的方位调谐特性和最优方位随刺激空间频率的不同而变化的方位调谐特性。结果表明,外膝体的非寻常的方位调谐特性并非主要由皮层下行投射所致,而是主要与先天遗传因素有关。     

单眼睑缝合1周建立形觉剥夺性弱视猫模型

目的比较正常组、模型组及对照组的图形视觉诱发电位(PVEP)和扫描视觉诱发电位(SVEP)视力,研究各组的视觉电生理表现,探讨单眼睑缝合1周是否可以建立形觉剥夺性弱视模型。方法分析三组PVEP的波形变化、潜时及完成一次诱发反应的时间;比较各组由SVEP得出的客观视力。结果①正常组PVEP由2个波峰组成“M型”(正向波向上),模型组及对照组出现波的分离—波形由多个波组成,而且完成一次反应的时间延长。②缝合侧的N75延迟,SVEP视力较正常组差且差别有统计学意义。③对照组未缝合侧视力恢复到正常水平而缝合侧视力仍差且与正常组有统计学差异。结论短期形觉剥夺的视觉电生理变化是弱视猫的一种表现,单眼睑缝合1周即可建立形觉剥夺性弱视猫的模型。     

猫外侧膝状体神经元HRP示踪结合生长抑素的免疫组织化学研究

本文采用HRP逆行示踪的方法,在猫视皮质的17区多点微量注射30％HRP,逆行标记外侧膝状体核（LGN）至视皮质的中继神经元,继用免疫金银法作生长抑素（SS）免疫组织化学,试图双标记LGN的中断神经元。结果显示：光镜下HRP标记细胞与SS是性细胞清晰可辨,HRP标记细胞内为较粗的棕色颗粒,分布于胞浆和树突基部;而SS免疫阳性细胞内的颗粒为银染黑色颗粒;HRP和SS双标记神经元内,上述两种颗粒共存,警备LGN的A、A1和C板层均有SS免疫阳性凶的分布;HRP标记细胞分布于A和A1板层;双标记神经元位于A和A1板层;C板层未见。本文结合以前的研究认为,SS在LGN至视皮质传导通路中的作用,可能与视觉信息的传递和调制有关。     

Behavioral effects of [4-norleucine, 7-D-phenylalanine]-alpha-melanocyte-stimulating hormone

The behavioral effects of alpha-melanocyte stimulating hormone (alpha-MSH) were compared to an alpha-MSH analogue that had a norleucine substituted for methionine in the four position and a D-phenylalanine substituted for L-phenylalanine in the seven position. [Nle4, D-Phe7]-alpha-MSH has previously been shown to be a superpotent agonist on melanocytes [17]. The present experiments indicate that [Nle4, D-Phe7]-alpha-MSH is equipotent to alpha-MSH in inducing grooming when administered intraventricularly. In contrast, the analogue has the opposite effect of alpha-MSH on performance of a visual discrimination task. alpha-MSH improves visual performance whereas [Nle4, D-Phe7]-alpha-MSH attenuates such performance. The contrasting activities of [Nle4, D-Phe7]-alpha-MSH on the physiological processes described suggest that this analogue may interact with three distinct melanotropin receptors in different ways. On melanocyte receptors the melanotropin analogue is a superagonist, on CNS melanotropin receptors involved in grooming it is equipotent to alpha-MSH, and on CNS receptors involved in attention, learning and memory [Nle4, D-Phe7]-alpha-MSH may be an antagonist of endogenous melanotropin.     

Adaptation and responses to changes in illumination by second- and third-order neurones of locust ocelli

Intracellular recordings have been made of responses to step, ramp and sinusoidal changes of light by second-order L-neurones and a third-order neurone, DNI, of locust (Locusta migratoria) ocelli.

Making learning easy: the acquisition of visual information during the orientation flights of social wasps

The flights of individual wasps (Vespula) were recorded as they approached a small feeder on the ground that was marked by a black cylinder ca 15 cm away. Two navigational strategies are used in these approaches. Initially, the wasp aims at the cylinder, treating it as a beacon and fixating it with frontal retina. In the last stage of the flight, the wasp assumes a preferred orientation so that the cylinder takes up a constant, more peripheral retinal position as the wasp nears the feeder. Path guidance by image-matching is likely to be limited to this final segment of the return. Wasps could gain the information needed for these distinct navigational strategies during the learning flights that they perform on their initial departures from the feeder. They fly away from the feeder in a series of arcs while turning at a mean angular velocity of 226°/s. The cylinder tends to be viewed with frontal retina during the arcs suggesting that the information required for aiming at the cylinder is acquired then. For image matching, the appearance of the cylinder needs to be learnt when the wasp is in the orientation that it adopts close to the feeder on its return flight. Wasps tend to assume this orientation during learning flights while they face the feeder. Such inspections of the feeder occur at the ends of arcs when a wasp's turning velocity is low.     

Alpha-melanocyte stimulating hormone facilitates learning of visual but not auditory discriminations

The neuropeptide alpha-MSH has been proposed to influence learning and memory by increasing visual attention. To test the possibility that MSH selectively affects visual learning, rats were tested in learning tasks in which the cues were either visual or auditory. Maze and bar-press tasks were used. MSH administration increased the rate of learning of the visual tasks, regardless of the task difficulty or the type of response required of the rat. MSH had no effect on the rate of learning of the auditory tasks. These results support the hypothesis that MSH facilitates learning by influencing some aspect of visual information processing.     

Adaptation to visual stimulation modifies the burst firing property of V1 neurons

The mean firing rate of visual cortical neurons is reduced after prolonged visual stimulation, but the underlying process by which this occurs as well as the biological significance of this phenomenon remains unknown. Computational neuroscience studies indicate that high-frequency bursts in stimulus-driven responses can be transmitted across synapses more reliably than isolated spikes, and thus may carry accurate stimulus-related information. Our research examined whether or not adaptation affects the burst firing property of visual cortical neurons by examining changes in the burst firing changes of V1 neurons during adaptation to the preferred visual stimulus. The results show that adaptation to prolonged visual stimulation significantly decreased burst frequency (bursts/s) and burst length (spikes/burst), but increased burst duration and the interspike interval within bursts. These results suggest that the adaptation of V1 neurons to visual stimulation may result in a decrease of feedforward response gain but an increase of functional activities from lateral and/or feedback connections, which could lead to a reduction in the effectiveness of adapted neurons in transmitting information to its driven neurons.     

应用基于内源信号的光学成像技术的视觉脑研究现状

基于脑内源信号的光学成像技术是近来国际上出现的一种脑功能成像方法。该技术既无毒,又具有较高的空间分辨率,因而被迅速应用于动物的视觉、听觉、体感皮层功能构筑的研究中。本文综述了这种光学脑功能成像在视觉脑研究方面所取得的重要进展,并分析了该方法与其他脑成像技术、微电极单细胞技术的关系。报道了国内自行研制第、套脑功能光学成像系统的研究工作,该系统已在猫初级视觉皮层不同深度获得了清晰的方位功能图,并已经和