Geisler Wilson S, Albrecht Duane G, Crane Alison M
Center for Perceptual Systems and Department of Psychology, University of Texas at Austin, Austin, Texas 78712, USA.
J Neurosci. 2007 May 9;27(19):5063-7. doi: 10.1523/JNEUROSCI.0835-07.2007.
During normal saccadic inspection of natural images, the receptive fields of cortical neurons are bombarded with frequent simultaneous changes in local mean luminance and contrast, yet there have been no systematic studies of how cortical neurons respond to such stimulation. The responses of single neurons in the primary visual cortex of the cat were measured for 200 ms presentations of sine-wave gratings confined to the conventional receptive field. Both local mean luminance and contrast were parametrically and randomly varied over the 1-1.5 log unit ranges that are typical of natural images. We find that responses are strongly modulated by both the local mean luminance and contrast, but in an approximately separable manner: the contrast response function is approximately invariant except for a scale factor that depends on the local mean luminance. The shape of the temporal response profiles were found to be approximately invariant with contrast, but were strongly affected by the local mean luminance. The results suggest that most, if not all, cortical neurons carry substantial local luminance information.
在对自然图像进行正常扫视检查期间，皮质神经元的感受野会频繁受到局部平均亮度和对比度同时变化的冲击，然而，尚未有关于皮质神经元如何响应这种刺激的系统性研究。针对局限于传统感受野的正弦波光栅进行200毫秒的呈现，测量了猫初级视觉皮层中单个神经元的反应。局部平均亮度和对比度在自然图像典型的1-1.5对数单位范围内进行参数化且随机变化。我们发现，反应受到局部平均亮度和对比度的强烈调制，但方式大致可分离：对比度反应函数除了依赖于局部平均亮度的比例因子外大致不变。发现时间反应轮廓的形状随对比度大致不变，但受到局部平均亮度的强烈影响。结果表明，即使不是全部，大多数皮质神经元都携带大量局部亮度信息。
