SPATIOTEMPORAL ORGANIZATION OF SIMPLE-CELL RECEPTIVE-FIELDS IN THE CATS STRIATE CORTEX .2. LINEARITY OF TEMPORAL AND SPATIAL SUMMATION
SPATIOTEMPORAL ORGANIZATION OF SIMPLE-CELL RECEPTIVE-FIELDS IN THE CATS STRIATE CORTEX .2. LINEARITY OF TEMPORAL AND SPATIAL SUMMATION
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DOI：
10.1152/jn.1993.69.4.1118
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发表时间：
1993-04-01
影响因子：
2.5
通讯作者：
FREEMAN, RD
中科院分区：
文献类型：
--
作者：
DEANGELIS, GC;OHZAWA, I;FREEMAN, RD
1.我们已经测试的假设，简单的细胞在猫的视觉皮层执行线性时空过滤的视觉图像。为了进行这项研究，我们注意到，如果对小的、短暂的闪光的响应通过傅立叶变换与正弦光栅刺激引起的响应在数学上相关，则视觉神经元的行为是线性的。我们已经评估了线性的时间和空间的总和为118个简单的细胞记录从成年猫和小猫在4岁和8周出生后的纹状皮质（区17）。这些神经元代表了一个子集的人口细胞，我们已经描述了出生后发展的时空感受场结构在前面的文件。时空感受场配置文件的构建，与使用的反向相关技术，从响应的随机序列的小酒吧刺激，比背景更亮或更暗。傅立叶分析的时空感受场分布产生线性预测的细胞的空间和时间的频率调谐。这些预测的响应进行了比较，通过使用漂移，正弦亮度光栅刺激测量的空间和时间频率调谐曲线。对于大多数简单的细胞，有很好的协议之间的空间和时间的频率调谐曲线预测的接收场分布和那些通过使用正弦光栅测量。这些结果表明，简单细胞内的空间和时间总和近似线性。有一种趋势，预测调谐曲线比测得的调谐曲线稍宽，这一发现是一致的阈值非线性的影响，在这些神经元的输出。然而，在某些情况下，预测的调谐曲线仅在低空间和时间频率下偏离测量的响应。这不能用简单的阈值非线性来解释。如果线性假设，它应该是可以预测的方向选择性的简单细胞从其时空感受场分布的结构。对于几乎所有的细胞，线性预测正确地确定了视觉刺激的首选运动方向。然而，在线性预测的基础上，方向性偏差的强度通常被低估了约2倍。考虑到对比度响应函数中揭示的扩展指数非线性，可以调和测量和预测方向选择性指数之间的差异。总体而言，这些研究结果表明，时空接收场配置文件与使用反向相关可用于预测简单的细胞的各种响应特性。这些结果通常与最近的理论工作相一致，其中简单的细胞被建模为线性时空滤波器，指数非线性和对比度归一化机制的组合。
1. We have tested the hypothesis that simple cells in the cat's visual cortex perform a linear spatiotemporal filtering of the visual image. To conduct this study we note that a visual neuron behaves linearly if the responses to small, brief flashes of light are mathematically related, via the Fourier transform, to the responses elicited by sinusoidal grating stimuli.2. We have evaluated the linearity of temporal and spatial summation for 118 simple cells recorded from the striate cortex (area 17) of adult cats and kittens at ages 4 and 8 wk postnatal. These neurons represent a subset of the population of cells for which we have described the postnatal development of spatiotemporal receptive-field structure in the preceding paper. Spatiotemporal receptive-field profiles are constructed, with the use of a reverse correlation technique, from the responses to random sequences of small bar stimuli that are brighter or darker than the background. Fourier analysis of spatiotemporal receptive-field profiles yields linear predictions of the cells' spatial and temporal frequency tuning. These predicted responses are compared with spatial and temporal frequency tuning curves measured by the use of drifting, sinusoidal-luminance grating stimuli.3. For most simple cells, there is good agreement between spatial and temporal frequency tuning curves predicted from the receptive-field profile and those measured by the use of sinusoidal gratings. These results suggest that both spatial and temporal summation within simple cells are approximately linear. There is a tendency for predicted tuning curves to be slightly broader than measured tuning curves, a finding that is consistent with the effects of a threshold nonlinearity at the output of these neurons. In some cases, however, predicted tuning curves deviate from measured responses only at low spatial and temporal frequencies. This cannot be explained by a simple threshold nonlinearity.4. If linearity is assumed, it should be possible to predict the direction selectivity of simple cells from the structure of their spatiotemporal receptive-field profiles. For virtually all cells, linear predictions correctly determine the preferred direction of motion of a visual stimulus. However, the strength of the directional bias is typically underestimated by a factor of about two on the basis of linear predictions. Consideration of the expansive exponential nonlinearity revealed in the contrast-response function permits a reconciliation of the discrepancy between measured and predicted direction selectivity indexes.5. Overall, these findings show that spatiotemporal receptive-field profiles obtained with the use of reverse correlation may be used to predict a variety of response properties for simple cells. These results are generally consistent with recent theoretical work in which simple cells are modeled as the combination of a linear spatiotemporal filter, an exponent nonlinearity, and a contrast normalization mechanism.