Chichilnisky E J, Kalmar R S
Systems Neurobiology, The Salk Institute and University of California, San Diego, La Jolla, California 92037, USA.
J Neurosci. 2003 Jul 30;23(17):6681-9. doi: 10.1523/JNEUROSCI.23-17-06681.2003.
Recent studies have examined the temporal precision of spiking in visual system neurons, but less is known about the time scale that is relevant for behaviorally important visual computations. We examined how spatiotemporal patterns of spikes in ensembles of primate retinal ganglion cells convey information about visual motion to the brain. The direction of motion of a bar was estimated by comparing the timing of responses in ensembles of parasol (magnocellular-projecting) retinal ganglion cells recorded simultaneously, using a cross-correlation approach similar to standard models of motion sensing. To identify the temporal resolution of motion signals, spike trains were low-pass filtered before estimating the direction of motion. The filter time constant that resulted in most accurate motion sensing was in the range of 10-50 msec for a range of stimulus speeds and contrasts and approached a lower limit of approximately 10 msec at high speeds and contrasts. This time constant was, on average, comparable to the length of interspike intervals. These findings suggest that cortical neurons could filter their inputs on a time scale of tens of milliseconds, rather than relying on the precise times of individual input spikes, to sense motion most reliably.
近期的研究探讨了视觉系统神经元放电的时间精度，但对于与行为重要的视觉计算相关的时间尺度，我们却知之甚少。我们研究了灵长类动物视网膜神经节细胞群体中动作电位的时空模式如何将视觉运动信息传递给大脑。通过使用类似于标准运动感知模型的互相关方法，比较同时记录的伞状（投射到 magnocellular 的）视网膜神经节细胞群体的反应时间，来估计一个条形物的运动方向。为了确定运动信号的时间分辨率，在估计运动方向之前，对动作电位序列进行低通滤波。对于一系列刺激速度和对比度，导致最准确运动感知的滤波器时间常数在 10 - 50 毫秒范围内，并且在高速和高对比度下接近约 10 毫秒的下限。这个时间常数平均而言与动作电位间隔的长度相当。这些发现表明，皮层神经元可以在几十毫秒的时间尺度上对其输入进行滤波，而不是依赖于单个输入动作电位的精确时间，以最可靠地感知运动。
