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     

GABA拮抗剂荷包牡丹碱对猫外膝体神经元方位调谐特性的影响

在十二只成年猫上用多管玻璃微电极记录了外膝体神经元对不同空间频率和不同方位的移动正弦光栅刺激的反应,共详细测定并对比研究了３８个方位敏感性细胞在微电泳荷包牡丹碱前后的方位调谐特性。在最优空间频率附近的较低空间频率下,微电泳荷包牡丹碱后,外膝体细胞的方位敏感性强度（Ｂｉａｓ）降低,而在截止频率附近的较高空间频率下,微电泳前后外膝细胞的方位敏感性强度（Ｂｉａｓ）从总体上看没有显著变化。结果表明,以空间频率为截止频率附近的移动正弦光栅作为刺激,外膝体细胞的方位敏感性可能主要是由视网膜神经节细胞的兴奋输入所形成,而非外膝体内抑制机制所致。     

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。     

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     

特定方位的光栅识别学习不改变猫外膝体背核神经元的方位敏感性

视觉信号识别训练可改变视觉通路神经元的可塑性, 其神经机制尚不清楚。已有少数研究显示, 动物(猴) 长时间进行特定方位的光栅识别学习后, 视皮层部分神经元对视觉刺激的反应表现出与学习任务相关的敏感性变化。这种敏感性变化是否亦存在于皮层下结构尚无报道。本实验训练两只成年猫分别进行水平和垂直方位的条形静止正弦光栅的识别以获得食物奖赏, 两只猫的行为识别能力逐渐提高, 4 个多月后识别的正确率达85%以上, 用与训练方位垂直的正弦光栅检测发现, 识别正确率明显下降。细胞外记录外膝体背核(Dorsal lat eral geniculate nucleus, dLGN) 神经元对不同方位正弦光栅刺激的反应显示, 与正常猫相比, 训练猫外膝体细胞的最优方位并未向着训练方位发生明显改变, 对于感受野位于中央区15度视角以内的细胞来说, 其方位选择性强度以及在训练方位的发放强度与正常猫无明显差异。以上结果表明, 猫对特定方位的光栅识别学习不改变外膝体神经元的方位敏感性, 其行为上方位识别特异性的提高可能与视皮层细胞的方位编码可塑性有关。     

视皮层反馈对猫外膝体神经元方位调制特性的影响

以扫描正弦光栅作为刺激,用冰冻法毁损皮层17、18、19区和外侧上雪氏回(LS区)来阻断皮层对外膝体的反馈投射,记录并描绘了猫外膝体597个细胞的方位调制特性.去视皮层猫外膝体神经元的平均方位选择性强度(Bias)为0.154,与正常猫(0.155)几乎相同,其最优方位偏向于水平方位.与正常猫外膝体不同的是,去视皮层猫外膝体失去了最优方位的切向分布规律,用GABA或KCl压抑皮层活动得到了相近的实验结果.结果说明正常外膝体的最优方位切向分布规律来自皮层反馈投射.     

猫视皮层神经元对光栅反应最优方位在视网膜上分布特性的研究

用金属微电极记录了114个猫皮层17、18区细胞对不同方位光栅图象刺激的反应。细胞最优方位与其感受野中心在视网膜的位置间有系统性关系,即最优方位总是倾向于垂直于各感受野中心与视网膜中心区(area centralis)的连线。这一规律对在18区或17、18区全体记录到的细胞而言,有统计意义。 在17、18区内,仅对于感受野位于视网膜离心度(eccentricity)大于9°视角的细胞、具有较窄感受野(宽度小于2.5°)的细胞以及感受野处于视网膜垂直经线附近的细胞,上述规律才有统计意义,而对感受野离心度小于9°的细胞、感受野宽度大于2.5°的细胞以及感受野在倾斜经线附近的细胞,上述规律不明显。     

猫外膝体神经元对光栅刺激方位倾向性的一种分布特性

我们检测了猫外膝体(LGN)神经元对闪烁方波光栅的反应与光栅方位的关系。对一定对比度和空间频率的光栅,26个记录到的神经元的反应均随方位不同而变化,其最大反应和最小反应的比值平均为3.0±0.3(S.E.)。神经元的最优方位(即引起最大反应的光栅方位)随其感受野中心在视网膜上的位置而异,具有平行于其各自感受野中心与视网膜中央区(area cen-sralis)的连接线的倾向。     

基于光敏蛋白的猫视皮层细胞双眼汇聚功能的模拟

已知光敏蛋白菌紫质ＬＢ膜具有类似于视觉系统感受野的对光微分响应。利用这个特性,本文组装了一对人工视皮层条型简单细胞感受野,并测定了其朝向选择特性及ＯＮ－区闪光融合频率响应特性。在此基础上,用这一对人工感受野组成了猫视皮层细胞双眼汇聚功能模拟系统,并模拟了猫视皮层细胞双眼汇聚功能。     

用菌紫质Langmuir—Blodgett膜模拟视网膜神经节细胞感受野的DOG滤波等特性

用菌紫质ＬＢ（Ｌａｎｇｍｕｉｒ—Ｂｌｏｄｇｅｔｔ）膜以一维形式模拟了视网膜神经节细胞的ＯＮ－中心型感受野。实验表明菌紫质ＬＢ膜具有ＯＮ型和ＯＦＦ型微分响应特性。对运动狭缝,所模拟的人工视网膜感受野的周边区和中心区都具有类高斯函数形式的滤波特性,整个人工视网膜感受野具有与高等动物视网膜相似的ＤＯＧ（ＤｉｆｆｅｒｅｎｃｅｏｆＧａｕｓｓｉａｎｓ）滤波运算功能。     

Statistics and geometry of orientation selectivity in primary visual cortex

Orientation maps are a prominent feature of the primary visual cortex of higher mammals. In macaques and cats, for example, preferred orientations of neurons are organized in a specific pattern, where cells with similar selectivity are clustered in iso-orientation domains. However, the map is not always continuous, and there are pinwheel-like singularities around which all orientations are arranged in an orderly fashion. Although subject of intense investigation for half a century now, it is still not entirely clear how these maps emerge and what function they might serve. Here, we suggest a new model of orientation selectivity that combines the geometry and statistics of clustered thalamocortical afferents to explain the emergence of orientation maps. We show that the model can generate spatial patterns of orientation selectivity closely resembling the maps found in cats or monkeys. Without any additional assumptions, we further show that the pattern of ocular dominance columns is inherently connected to the spatial pattern of orientation.     

Dynamics of orientational tuning of cat visual cortical neurons

Orientational tuning of primary visual cortical unit activity was investigated in acute experiments on cats immobilized by a muscle relaxant, by the time slices method. Poststimulus histograms of responses of a neuron to presentation of a flashing bar of light in the center of its receptive field, with different orientations, were plotted; graphs of orientational tuning with respect to mean discharge frequency in consecutive time cuts of the responses with a 10 or 20 msec step were then plotted. Orientational tuning in all cortical neurons studied exhibited considerable dynamic changes in sharpness and preferred orientation. In two thirds of cells an effect of scanning a certain part of the range of orientations was observed, in the form of a successive shift of the maximum of the orientational tuning curve from some preferred orientations to others was discovered. The possible functional significance of spike discharges of visual cortical neurons is discussed.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 13, No. 5, pp. 451–459, September–October, 1981.     

猫外膝体神经元非寻常的方位调谐特性——Ⅰ、在正常猫的研究

在九只成年猫上用玻璃电极记录了单个外膝体神经元对不同方位的移动正弦光栅刺激的反应共详细测定了４００个细胞的方位调谐特性。少数外膝体神经元具有非寻常的方位调谐特性,包括：具蝴蝶状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光栅空间频率的改变而变化的方位调谐特性。这些细胞非寻常的方位调谐特性往往伴随着非寻常的空间频率调谐特性。空们的方位调谐特性和空间频率调谐特性都不能用Ｓｏｏｄａｋ等提     

冷冻取消胼胝体传递对猫皮层17/18区边界细胞部分电生理特性的影响

用IBM-XT微机控制产生各种取向的可移动正弦光栅作为视觉刺激,用金属微电极在猫皮层一侧17/18区边界附近进行胞外记录,神经信号由微机实时采集并进行数据处理;对11只猫的62个细胞进行了冷冻取消另一侧胼胝体向记录侧传递前后细胞的取向选择性,最佳取向和最大反应的测定与比较.发现冷冻后有至少50%细胞的取向选择性强度发生了变化,其中选择性减少与增加的数目基本相等;有20-30%细胞的最佳取向发产了10°至20°的变化;有一半以上细胞的最大反应发生了变化,其中三分之二细胞的反应减少,其余的增加.通过部分细胞的恢复实验证明以上变化基本是可逆的,说明胼胝体对这些特性有一定影响.     

Development of stimulus selectivity and functional organization in the suprasylvian visual cortex of the cat

We have recorded from single neurons in the medial bank of the middle suprasylvian sulcus (PMLS) of anaesthetized and paralysed cats aged between nine days and eight weeks. Visual responses were assessed qualitatively, by using conventional projected stimuli, and quantitatively for drifting, high-contrast gratings of optimum spatial and temporal frequencies, but varying in orientation and direction of drift. At 9 days of age, some cells in the PMLS were spontaneously active but in three long penetrations only one visually responsive neuron was isolated. Between 9 and 15 days there was a rapid increase in the proportion of responsive units, which first appeared in small clusters in the lower layers (IV, V, VI). During the second and third postnatal weeks, spontaneous activity and the strength of visual responses increased to adult levels, and the proportion of cells showing rapid habituation to visual stimulation decreased. Even before two weeks of age, at least 85% of responsive cells in the PMLS were selective, by quantitative criteria, for image motion along one particular axis, and a majority of these were clearly direction-selective (responding to movement in one direction significantly more strongly than to that in the opposite). By the end of the third postnatal week the proportion of units with strong direction preference reached adult levels. The selective cells were initially more broadly 'tuned', on average, for the direction of motion of a grating (mean half-width in animals of 10-12 days was 32.6 degrees), but the sharpness of tuning improved to reach the adult level (ca. 23 degrees) during the third postnatal week. In animals younger than three weeks a slightly smaller proportion of cells than in adults (but always more than one third of all visually responsive cells) responded to stationary, contrast-modulated gratings. The majority of these cells showed clear selectivity for the orientation of a flashed grating. A few 'non-selective' cells were found in the youngest animals but by the end of the third postnatal week virtually all cells responsive to stationary gratings displayed orientation selectivity. There was always good agreement between the preferred orientations for stationary and drifting gratings. Even before two weeks of age, when responsive cells occurred only in small clusters, there was a clear tendency for neighbouring neurons to have similar or opposite preferred directions, just as in adult cats. By 2-3 weeks of age there were clear progressive shifts in stimulus preference along oblique or tangential tracks.(ABSTRACT TRUNCATED AT 400 WORDS)     

Similarity of visual selectivity among clonally related neurons in visual cortex

Neurons in rodent visual cortex are organized in a salt-and-pepper fashion for orientation selectivity, but it is still unknown how this functional architecture develops. A recent study reported that the progeny of single cortical progenitor cells are preferentially connected in the postnatal cortex. If these neurons acquire similar selectivity through their connections, a salt-and-pepper organization may be generated, because neurons derived from different progenitors are intermingled in rodents. Here we investigated whether clonally related cells have similar preferred orientation by using a transgenic mouse, which labels all the progeny of single cortical progenitor cells. We found that preferred orientations of clonally related cells are similar to each other, suggesting that cell lineage is involved in the development of response selectivity of neurons in the cortex. However, not all clonally related cells share response selectivity, suggesting that cell lineage is not the only determinant of response selectivity.     

Horizontal organization of orientation-sensitive cells in primate visual cortex

In the visual cortex of the monkey the horizontal organization of the preferred orientations of orientation-selective cells follows two opposing rules:(1) neighbors tend to have similar orientation preferences, and(2) many different orientations are observed in a local region. We have described a classification for orientation maps based on the types of topological singularities and the spacing of these singularities relative to the cytochrome oxidase blobs. Using the orientation drift rate as a measure we have compared simulated orientation maps to published records of horizontal electrode recordings.     

"Timers" and "scanners" among orientation detectors in cat visual cortex

Experiments were carried out on immobilized cats to determine whether, among visual cortical neurons, besides the "scanners" described by the writers previously, which are responsible for a dynamic shift of preferred orientation, there exist also "timer" cells, which do not change the temporal parameters of their responses during rotation of a flashing stimulus. The existence of such cells is postulated on the basis of the previous hypothesis on the spatiotemporal principle of orientational coding. Of 76 neurons tested 27, i.e., 36%, were classed as "timers." They differed significantly from the "scanners" (64%) by the following properties: shorter latent periods, shorter time to the peak and duration of responses, more rapid rise of discharge frequently in the volley. The "timers" had less sharp orientational tuning and a low ratio between values of responses to presentation of preferred and worst stimuli (on account of a considerable increase in responses to unpreferred orientations). The set of preferred orientations of the "timers" was found to be highly selective and additional relative to the corresponding distribution for "scanners."The difference in frequency-temporal properties of responses and orientational tuning of the "timers" and "scanners" and their possible mutually complementary role in orientational coding at the visual cortical level are discussed.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 17, No. 1, pp. 35–43, January–February, 1985.     

The visual cortex "on command": 2 modes of operation of neuronal mechanisms (a topical article)]

Orientation tuning (TO) of 152 single units in the 17th area of cat cerebral cortex was studied under different contrasts of the light bar flashed in RF (2.3, 10 and 100) and also under local and general anaesthesia (Sombrevin, 4 mg/kg or Nembutal, 35 mg/kg). An invariance of preferred orientation to contrast or anaesthesia was revealed in 40-50% of cells. Noninvariant cells shifted significantly their preferred orientation on 22-90 degrees. Invariant units more often have a simple RF, more sharp OT and preferred horizontal and vertical orientations. Under the low-contrast conditions or under general anaesthesia, noninvariant neurons shifted their preferred diagonal orientations. Different role of the two neuronal groups in detection of the reper (horizontal and vertical) and other orientations in a normal conditions (high-contrast, alert state) in comparison with their behavior under worse conditions (low-contrast, narcosis or sleep) is discussed.     

Differences in orientation and receptive field position between supra- and infragranular cells of cat striate cortex and their possible functional implications

On the postlateral gyrus of the cat striate cortex the cells' preferred orientation and the location of their receptive fields was measured as a function of cortical depth in penetrations as parallel as possible to the radiating fibres. In most penetrations the majority of infragranular cells showed orientation preferences 45 degrees-90 degrees different from the preferred orientations of supragranular cells. In addition, aggregate receptive fields from the same eye of supra- and infragranular cells were spatially shifted against each other. Using different columnar models these results are discussed in terms of spatial contrast enhancement for two parallel mechanisms in upper and lower layers, determined for pattern discrimination and movement detection.