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1.
视网膜神经节细胞空间传输特性的模拟   总被引:2,自引:0,他引:2  
以新近提出的同心圆感受野模型为基础。从感受野大工上周区内各亚区之间的抑制性相互作用入手,对视网膜神经节细胞的各种空间传输特性进行了模拟,通过改变外周亚区间抑制性相互作用的敏感度和有效范围,可逼真地模拟神经节细胞的各种不同的面积反应函数,用该模型来处不同空间频率的正弦光栅时,它既能很好地传递图像的高频成份,又可十分有效地提升被感受野中心/外周拮抗机制所衰减了的低频信息,此外,由于该模型引进了外周亚区  相似文献   

2.
用双重正弦调制移动光栅图形研究了猫皮层18区神经元整合野特性。同在17区所观察到的结果一样,在18区神经元传统感受野(CRF)的外面,也存在着大范围的易化或抑制性整合野(IF)。抑制和易化性IF神经元分别占70%和30%。IF对刺激光栅的时间频率、空间频率、方位和方向都有选择性。对大多数细胞来说,IF的这些调谐特性都与其对应的CRF的特性相似。以上结果提示,18区神经元能够对CRF和IF内的图形特征进行整合,这种整合在复杂图形识别中起重要作用。  相似文献   

3.
Yu HB  Shou TD 《生理学报》2000,52(5):411-415
采用基于内源信号的脑光学成像方法,在大范围视皮层研究了不同空间拓扑位置对应的皮层区的对光栅刺激空间频率反应特性。结果表明,周边视野对应区对高空间频率刺激反应极弱或没有反应,中心视野对应区对较宽的空间频率范围内的刺激均有反应,但对高频刺激反应更强;无论在周边对应区还是中心对应区,其视野越靠近中心,其空间频率调谐曲线和截止空间频率越靠近高频,而且这种过渡是平缓的。以上结果说明,猫初级视皮层空间频率反应  相似文献   

4.
郭昆  李朝义 《生理学报》1993,45(6):543-551
用定量的心理物理测量方法,研究了错觉图形组成成分间的亮度对比和颜色对比方位错觉、长度觉及面积错觉幅度的影响。测试结果表明:与通常的错觉效应相比,当错觉图形组成成分间存在亮度对比或颜色对比(等亮度)时,受试者的错觉程度明显降低;其中,当存在颜色对比时,方位错觉的下降幅度更为显著,达到69.3%。此外还观察到,在单纯亮度对比条件下,只需1.8%和5.3%的低对比度即可分别产生轮廓和边缘错觉;但在等亮度  相似文献   

5.
通过测量感受野内不同空间位置的时间传递函数,研究了猫18区简单细胞感受野的时空结构.不同位置在时间特性上的差异主要表现在绝对相移上.绝对相移与位置的关系有两类:一类随位置变化绝对相移呈现连续性改变;另一类随位置变化绝对相移发生180度跳变.将频域特性进行反Fourier变换可得到感受野在时空域的表达.连续变化型的时间特性和空问特性不能分离,其时空结构倾斜.跳变型的时空特性可以分离,在时空平面内不具有倾斜结构.根据感受野内不同位置的绝对相移可以预测神经元的最佳运动方向和最佳空间频率.  相似文献   

6.
用正弦调制的光栅图形研究了猫纹状皮层神经元传统感受野外区域(整合野)的亚区结构,整合野不同亚区的作用可表现为抑制或易化。根据端区和侧区的作用性质,整合野有4种不同的结构形式。在端区和侧区的内部以及在这两个区域之间,空间总合显示非线性特性。其非线性程度随刺激面积的增加而变大,表明在整合野的亚区内和亚区间存在着相互抑制。  相似文献   

7.
在视觉传入通路中,各级神经元对视觉图象的传递和加工起着不同的作用。视网膜和外膝体细胞能传递图象的平均亮度,增强边缘和拐角;初级视皮层细胞能检测图象的基本特征,即线条/边缘的方位、运动方向、空间频率和深度等;高级视皮层细胞能对基本特征进行整合,从而反应复杂图形的整体特性。在视皮层内,调谐特性相同的细胞在垂直方向上排列成规则的“功能柱”结构,各种不同的功能柱组合成“超柱”,它可能是分析图象的基本功能单元.  相似文献   

8.
听觉前向掩蔽效应是听觉动态非线性的重要表现, 也是听觉适应机制的重要表现, 由此产生听觉前后向参考编码机制,而传统的语音信号处理机制是帧与帧独立的线性处理方式,所以不能反映实际听觉系统的动态非线性适应特性。传统的听觉模型对这种动态非线性适应机制的模拟是通过自适应调节听觉耳蜗滤波器的增益来完成的, 这不管在计算量上还是在滤波器的稳定性设计上都有其缺陷。我们根据听觉的生理学机制,建立前馈自适应模型,从输入输出特性曲线上引出静态增益曲线,再在静态增益曲线上引入动态过程,由此建立的数学模型,利用心理学试验数据得到模型参数。试验结果表明,该模型能够很好地预测前向掩蔽效应,对听觉的动态非线性适应机制是一种很好的解释。  相似文献   

9.
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。  相似文献   

10.
1.用玻璃绝缘的钨丝电极作细胞外记录,研究不了麻醉猫视皮层17区单个细胞对栅形刺激反应的某些特点。先用光学投影仪在屏幕上投影各种图形以确定细胞感受野位置,并对该细胞感受野性质作一般观察。随后用以电视监示器改装的方波——正弦波栅形发生器提供刺激,研究此细胞的空间频率-反应特性及对比度-反应特性。 2.所有对正弦波栅形有反应和空间频率选择性的细胞同样对方波栅形也有反应和空间频率选择性。它们的最优频率一致。简单细胞的通频带比复杂细胞的略窄。 3.绝大多数细胞对方波栅形的反应都比对同样条件下的正弦栅形反应大(1.33∶1),对比阈值低。 4.记录到少数细胞(7/54,6个为复杂型,1个类型不明),其方波栅形的频率-反应曲线与正弦波栅形的比较,两种反应在低频端有更大的差别,当把栅形对比度降低为接近阈值水平时,这个差别显著变小.  相似文献   

11.
12.
感受野是视觉系统信息处理的基本结构和功能单元。X、Y细胞是两类主要的视网膜神经节细胞。生理实验发现,在经典感受野之外还存在一个大范围的在周边去抑制区。文中采用周边去抑制区对经典外周的去抑制非线性使用方式,建立一个二维的与实验结果联系紧密的X、Y细胞统一的复合感受野模型。该模型不仅能模拟X细胞的null-test反应和Y细胞的on-off反应,还模拟了Y细胞在低空频刺激时的信频反应、圆面积空间的倍频  相似文献   

13.
1965年Barlow & Levick及我国科技工作者分别独立提出了原理大致相同的方向检测感受野模型,但其数学模型却一直未见有报道.本文用数量场方法给出了其数学模型,这是一个Gabor函数模型,并据此解释了方向检测感受野的方向调谐曲线以及方向检测通道数量问题.  相似文献   

14.
Mante V  Bonin V  Carandini M 《Neuron》2008,58(4):625-638
Functional models of the early visual system should predict responses not only to simple artificial stimuli but also to sequences of complex natural scenes. An ideal testbed for such models is the lateral geniculate nucleus (LGN). Mechanisms shaping LGN responses include the linear receptive field and two fast adaptation processes, sensitive to luminance and contrast. We propose a compact functional model for these mechanisms that operates on sequences of arbitrary images. With the same parameters that fit the firing rate responses to simple stimuli, it predicts the bulk of the firing rate responses to complex stimuli, including natural scenes. Further improvements could result by adding a spiking mechanism, possibly one capable of bursts, but not by adding mechanisms of slow adaptation. We conclude that up to the LGN the responses to natural scenes can be largely explained through insights gained with simple artificial stimuli.  相似文献   

15.
李朝义  张一虹 《生理学报》1986,38(4):345-356
用不同频率正弦波调制发光二极管亮度,刺激猫外膝体细胞的感受野中心。用Apple-Ⅱplus 计算机将细胞放电频率的瞬时变化作成反应直方图(PSTH)。通过傅里叶变换,计算平均放电率、基波幅度和高次谐波幅度的变化,定量地研究了细胞反应的线性和非线性性质。 1.在恒定的平均亮度下,持续细胞的反应具有较好的线性特征,表现在PSTH可以重现正弦光刺激的频率和波形;与此相反,瞬变细胞的反应显示明显的非线性性质,PSTH出现半波整流波形,反应上升相交陡而下降相较平缓。 2.两类细胞对正弦刺激的反应具有不同的谐波成分:典型持续细胞的反应中主要包含基波成分,高次谐波的幅度接近噪声水平;但是,瞬变细胞的谐波可以延续到8次之多,二次和三次谐波的幅度可高达基波幅度的50%。 3.逐渐增加调制光刺激的平均亮度,持续细胞反应中二次谐波幅度始终保持在很低的水平上,而瞬变细胞的谐波幅度则随着增大。 4.增加光刺激的调制深度,持续细胞的反应特点是:(1)平均放电率保持不变或略有增加,(2)二次谐波增长很慢,(3)基频相位基本保持不变。与此相反,瞬变细胞的平均放电率和二次谐波幅度都随调制深度增加而明显地增大,并且基波相位也可见到较明显的前移。 以上结果表明,持续细胞与瞬变细胞在时间域方面也具有线性和非线性的差别。  相似文献   

16.
Brightness contrast effects shown by single cells in the macaque's lateral geniculate nucleus were studied with black and white lines of various widths, consisting of either: (1) "simultaneous contrast" stimuli in which the line was produced by luminance changes in the flanking areas or (2) "successive contrast" stimuli in which the line itself changed in luminance. Line widths that gave optimal responses and response magnitudes themselves were similar for the two types of stimulus, except for the widest lines used (2 degrees). Thus, simultaneous brightness contrast is a primary determinant of the response of primate LGN cells but only within 2 degrees of the center of the receptive field. Neural processing up to this level cannot therefore explain the long distance effects of simultaneous brightness contrast in human perception.  相似文献   

17.
Within vision research retinotopic mapping and the more general receptive field estimation approach constitute not only an active field of research in itself but also underlie a plethora of interesting applications. This necessitates not only good estimation of population receptive fields (pRFs) but also that these receptive fields are consistent across time rather than dynamically changing. It is therefore of interest to maximize the accuracy with which population receptive fields can be estimated in a functional magnetic resonance imaging (fMRI) setting. This, in turn, requires an adequate estimation framework providing the data for population receptive field mapping. More specifically, adequate decisions with regard to stimulus choice and mode of presentation need to be made. Additionally, it needs to be evaluated whether the stimulation protocol should entail mean luminance periods and whether it is advantageous to average the blood oxygenation level dependent (BOLD) signal across stimulus cycles or not. By systematically studying the effects of these decisions on pRF estimates in an empirical as well as simulation setting we come to the conclusion that a bar stimulus presented at random positions and interspersed with mean luminance periods is generally most favorable. Finally, using this optimal estimation framework we furthermore tested the assumption of temporal consistency of population receptive fields. We show that the estimation of pRFs from two temporally separated sessions leads to highly similar pRF parameters.  相似文献   

18.
19.
PURPOSE: Does a physiologically plausible model of the retinal ganglion cell (RGC) receptive field (RF) predict the spatial tuning properties of the Hermann Grid Illusion (HGI)? METHODS: The spatial tuning of a single intersection HGI was measured psychophysically in normal observers using a nulling technique at different vertical grid line luminances. We used a model based upon a standard RGC RF, balanced to produce zero response under uniform illumination, to predict the response of the model cell to the equivalent range of stimulus conditions when placed in either the 'street' or the 'intersection' of a single element of a Hermann grid. We determined the equivalent of the nulling luminance required to balance these responses and minimise the HGI. RESULTS: The model and the psychophysical data demonstrated broad spatial tuning with similarly shaped tuning profiles and similar strengths of illusion. The line width at the peak of the model tuning function was around twice the model RGC RF centre size. Modelling the psychophysical functions gave RF centre sizes smaller than expected from human anatomical evidence but similar to that suggested by primate physiological evidence. In the model and psychophysically the strength of the illusion varied with the luminance of the vertical grid line when HGI strength was expressed as a Michelson nulling contrast, but this effect was smaller when HGI strength was expressed as a nulling luminance. CONCLUSIONS: The shape, width, height and position of the spatial tuning function of the HGI can be well modelled by a RGC RF based model. The broad tuning of these functions does not appear to require a broad range of different cell sizes either in the retina or later in the visual pathway.  相似文献   

20.
Li H  Liu WZ  Liang PJ 《PloS one》2012,7(3):e34336
Nearby retinal ganglion cells of similar functional subtype have a tendency to discharge spikes in synchrony. The synchronized activity is involved in encoding some aspects of visual input. On the other hand, neurons always continuously adjust their activities in adaptation to some features of visual stimulation, including mean ambient light, contrast level, etc. Previous studies on adaptation were primarily focused on single neuronal activity, however, it is also intriguing to investigate the adaptation process in population neuronal activities. In the present study, by using multi-electrode recording system, we simultaneously recorded spike discharges from a group of dimming detectors (OFF-sustained type ganglion cells) in bullfrog retina. The changes in receptive field properties and synchronization strength during contrast adaptation were analyzed. It was found that, when perfused using normal Ringer's solution, single neuronal receptive field size was reduced during contrast adaptation, which was accompanied by weakening in synchronization strength between adjacent neurons' activities. When dopamine (1 μM) was applied, the adaptation-related receptive field area shrinkage and synchronization weakening were both eliminated. The activation of D1 receptor was involved in the adaptation-related modulation of synchronization and receptive field. Our results thus suggest that the size of single neuron's receptive field is positively related to the strength of its synchronized activity with its neighboring neurons, and the dopaminergic pathway is responsible for the modulation of receptive field property and synchronous activity of the ganglion cells during the adaptation process.  相似文献   

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