CONTRAST GAIN-CONTROL IN THE CATS VISUAL-SYSTEM
CONTRAST GAIN-CONTROL IN THE CATS VISUAL-SYSTEM
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DOI：
10.1152/jn.1985.54.3.651
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发表时间：
1985-01-01
影响因子：
2.5
通讯作者：
FREEMAN, RD
中科院分区：
文献类型：
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作者：
OHZAWA, I;SCLAR, G;FREEMAN, RD
1. 我们已经研究了皮层神经元对视觉刺激的局部对比度水平的适应在功能上是有利的。具体来说，皮质细胞可能具有较大的差异对比灵敏度，这是由于将有限的反应范围集中在平均常数水平附近进行调整的结果。2. 为了评估这一概念，我们测量了纹状皮层细胞的对比反应功能，同时系统地使它们适应不同的刺激光栅的对比水平。3. 对于大多数被测试的皮质神经元，这个基本实验的结果表明，对比-反应函数沿着对数-对比轴横向移动，从而使反应函数与刺激中的平均对比水平相匹配。这意味着在细胞的对比-响应关系的增益中有一个依赖于对比的变化。我们将这些过程定义为对比度增益控制。4. 这种对比度调整的程度因细胞而异。细胞类型（简单与复杂）或层状分布无明显差异。5. 对比度增益控制几乎肯定是一种皮质功能，因为外侧膝状细胞和纤维只表现出最小的影响。随附论文（37）中提出的测试为该过程的皮层起源提供了额外的证据。6. 在另一系列实验中，对比适应对对比敏感度生理估计的影响进行了评估。持续适应低至3%的对比度水平能够使大多数测试细胞的阈值几乎翻倍。因此，适应可能是决定皮质神经元对比敏感度的一个重要因素。7. 我们测试了负责这些增益控制效应的机制的空间范围，通过尝试使用大光栅和光栅片来适应细胞，这些光栅片限制在细胞接受野的那一部分，兴奋性放电可以直接被激发（中央放电区）。适应性被发现是中部地区独有的特性。这甚至在超复杂细胞的情况下也是如此，它受到视野周围区域的强烈影响。8. 最后，我们测量了对比适应的时间过程。我们发现这个过程相当缓慢，平均时间常数约为。6 s。再一次，这个值在不同的细胞之间有相当大的差异。
1. We have examined the idea that the adaptation of cortical neurons to local contrast levels in a visual stimulus is functionally advantageous. Specifically, cortical cells may have large differential contrast sensitivity as a result of adjustments that center a limited response range around a mean level of constant. 2. To evaluate this notion, we measured contrast-response functions of cells in striate cortex while systematically adapting them to different contrast levels of stimulus gratings. 3. For the majority of cortical neurons tested, the results of this basic experiment show that contrast-response functions shift laterally along a log-contrast axis so that response functions match mean contrast levels in the stimulus. This implies a contrast-dependent change in the gain of the cell''s contrast-response relationship. We define these process as contrast gain control. 4. The degree to which this contrast adjustment occurs varies considerably from cell to cell. There are no obvious differences regarding cell type (simple vs. complex) or laminar distribution. 5. Contrast gain control is almost certainly a cortical function, since lateral geniculate cells and fibers exhibit only minimal effects. Tests presented in the accompanying paper (37) provide additional evidence on the cortical origin of the process. 6. In another series of experiments, the effect of contrast adaptation on physiological estimates of contrast sensitivity was evaluated. Sustained adaptation to contrast levels as low as 3% was capable of nearly doubling the thresholds of most of the cells tested. Adaptation may therefore be an important factor in determinations of the contrast sensitivity of cortical neurons. 7. We tested the spatial extent of the mechanisms responsible for these gain-control effects by attempting to adapt cells using both a large grating and a grating patch limited to that portion of a cell''s receptive field from which excitatory discharges could be elicited directly (the central discharge region). Adaptation was found to be an exclusive property of the central region. This held even in the case of hypercomplex cells, which received strong influences from surrounding regions of the visual field. 8. Finally, we measured the time course of contrast adaptation. We found the process to be rather slow, with a mean time constant of .apprx. 6 s. Once again, there was considerable variability in this value from cell to cell.