Research School of Biology, Australian National University, Canberra, Australian Capital Territory, Australia.
J Neurophysiol. 2010 May;103(5):2642-51. doi: 10.1152/jn.00591.2009. Epub 2010 Jan 6.
Motion processing in visual neurons is often understood in terms of how they integrate light stimuli in space and time. These integrative properties, known as the spatiotemporal receptive fields (STRFs), are sometimes obtained using white-noise techniques where a continuous random contrast sequence is delivered to each spatial location within the cell's field of view. In contrast, motion stimuli such as moving bars are usually presented intermittently. Here we compare the STRF prediction of a neuron's response to a moving bar with the measured response in second-order interneurons (L-neurons) of dragonfly ocelli (simple eyes). These low-latency neurons transmit sudden changes in intensity and motion information to mediate flight and gaze stabilization reflexes. A white-noise analysis is made of the responses of L-neurons to random bar stimuli delivered either every frame (densely) or intermittently (sparsely) with a temporal sequence matched to the bar motion stimulus. Linear STRFs estimated using the sparse stimulus were significantly better at predicting the responses to moving bars than the STRFs estimated using a traditional dense white-noise stimulus, even when second-order nonlinear terms were added. Our results strongly suggest that visual adaptation significantly modifies the linear STRF properties of L-neurons in dragonfly ocelli during dense white-noise stimulation. We discuss the ability to predict the responses of visual neurons to arbitrary stimuli based on white-noise analysis. We also discuss the likely functional advantages that adaptive receptive field structures provide for stabilizing attitude during hover and forward flight in dragonflies.
视觉神经元的运动处理通常被理解为它们如何整合空间和时间中的光刺激。这些综合特性，即时空感受野（STRF），有时可以通过白噪声技术获得，其中连续的随机对比度序列被传递到细胞视野内的每个空间位置。相比之下，运动刺激，如移动的条形物，通常是间歇性呈现的。在这里，我们将神经元对移动条形物的反应的 STRF 预测与蜻蜓小眼（简单眼）的二级中间神经元（L-神经元）的测量反应进行了比较。这些低延迟神经元将强度和运动信息的突然变化传递到飞行和凝视稳定反射中。对 L-神经元对随机条形物刺激的反应进行了白噪声分析，这些条形物刺激要么以每帧（密集）的方式，要么以与条形物运动刺激匹配的时间序列（稀疏）的方式间歇性地呈现。使用稀疏刺激估计的线性 STRF 能够更好地预测对移动条形物的反应，而使用传统密集白噪声刺激估计的 STRF 则更好，即使添加了二阶非线性项。我们的结果强烈表明，在密集的白噪声刺激期间，视觉适应会显著改变蜻蜓小眼 L-神经元的线性 STRF 特性。我们讨论了基于白噪声分析预测视觉神经元对任意刺激的反应的能力。我们还讨论了自适应感受野结构在蜻蜓悬停和前飞期间稳定姿态可能提供的功能优势。
