Mechler F, Victor J D, Purpura K P, Shapley R
Department of Neurology and Neuroscience, Cornell University Medical College, New York, New York 10021, USA.
J Neurosci. 1998 Aug 15;18(16):6583-98. doi: 10.1523/JNEUROSCI.18-16-06583.1998.
We show that spike timing adds to the information content of spike trains for transiently presented stimuli but not for comparable steady-state stimuli, even if the latter elicit transient responses. Contrast responses of 22 single neurons in macaque V1 to periodic presentation of steady-state stimuli (drifting sinusoidal gratings) and transient stimuli (drifting edges) of optimal spatiotemporal parameters were recorded extracellularly. The responses were analyzed for contrast-dependent clustering in spaces determined by metrics sensitive to the temporal structure of spike trains. Two types of metrics, cost-based spike time metrics and metrics based on Fourier harmonics of the response, were used. With both families of metrics, temporal coding of contrast is lacking in responses to drifting sinusoidal gratings of most (simple and complex) V1 neurons. However, two-thirds of all neurons, mostly complex cells, displayed significant temporal coding of contrast for edge stimuli. The Fourier metrics indicated that different response harmonics are partially independent, and their combined use increases information about transient stimuli. Our results demonstrate the importance of stimulus transience for temporal coding. This finding is significant for natural vision because moving edges, which are present in moving object boundaries, and saccades induce transients. We think that an abrupt change in the adapted state of the local visual circuitry triggers the temporal structuring of spike trains in V1 neurons.
我们发现，对于短暂呈现的刺激，脉冲发放时间增加了脉冲序列的信息含量，但对于类似的稳态刺激则不然，即使后者会引发瞬态反应。在猕猴V1区，细胞外记录了22个单神经元对具有最佳时空参数的稳态刺激（漂移正弦光栅）和瞬态刺激（漂移边缘）的周期性呈现的对比反应。在由对脉冲序列时间结构敏感的度量所确定的空间中，对反应进行对比依赖性聚类分析。使用了两种类型的度量，基于成本的脉冲发放时间度量和基于反应傅里叶谐波的度量。使用这两类度量时，大多数（简单和复杂）V1神经元对漂移正弦光栅的反应中缺乏对比的时间编码。然而，所有神经元中有三分之二，大多是复杂细胞，对边缘刺激显示出显著的对比时间编码。傅里叶度量表明不同的反应谐波部分独立，并且它们的联合使用增加了关于瞬态刺激的信息。我们的结果证明了刺激瞬态对时间编码的重要性。这一发现对于自然视觉很重要，因为运动物体边界中存在的运动边缘和扫视会引发瞬态。我们认为局部视觉回路适应状态的突然变化会触发V1神经元中脉冲序列的时间结构。
