Department of Physiology, Institute of Basic Medical Sciences, University of Oslo, N-0317 Oslo, Norway.
Neuroscience. 2013 Jul 9;242:85-96. doi: 10.1016/j.neuroscience.2013.03.037. Epub 2013 Mar 29.
Processing of visual information in the brain seems to proceed from initial fast but coarse to subsequent detailed processing. Such coarse-to-fine changes appear also in the response of single neurons in the visual pathway. In the dorsal lateral geniculate nucleus (dLGN), there is a dynamic change in the receptive field (RF) properties of neurons during visual stimulation. During a stimulus flash centered on the RF, the width of the RF-center, presumably related to spatial resolution, changes rapidly from large to small in an initial transient response component. In a subsequent sustained component, the RF-center width is rather stable apart from an initial slight widening. Several brainstem nuclei modulate the geniculocortical transmission in a state-dependent manner. Thus, modulatory input from cholinergic neurons in the peribrachial brainstem region (PBR) enhances the geniculocortical transmission during arousal. We studied whether such input also influences the dynamic RF-changes during visual stimulation. We compared dynamic changes of RF-center width of dLGN neurons during brief stimulus presentation in a control condition, with changes during combined presentation of the visual stimulus and electrical PBR-stimulation. The major finding was that PBR-stimulation gave an advancement of the dynamic change of the RF-center width such that the different response components occurred earlier. Consistent with previous studies, we also found that PBR-stimulation increased the gain of firing rate during the sustained response component. However, this increase of gain was particularly strong in the transition from the transient to the sustained component at the time when the center width was minimal. The results suggest that increased modulatory PBR-input not only increase the gain of the geniculocortical transmission, but also contributes to faster dynamics of transmission. We discuss implications for possible effects on visual spatial resolution.
大脑中视觉信息的处理似乎是从初始的快速但粗糙到后续的详细处理。这种从粗到细的变化也出现在视觉通路中单神经元的反应中。在背外侧膝状体核 (dLGN) 中，神经元的感受野 (RF) 特性在视觉刺激期间会发生动态变化。在以 RF 为中心的刺激闪光期间，RF 中心的宽度，大概与空间分辨率有关，在初始瞬态反应成分中会迅速从大变小。在随后的持续成分中，RF 中心的宽度除了初始稍微变宽外相当稳定。几个脑干核以状态依赖的方式调节膝状体皮质的传递。因此，来自脑桥旁脑干区域 (PBR) 的胆碱能神经元的调制输入在觉醒期间增强了膝状体皮质的传递。我们研究了这种输入是否也会影响视觉刺激期间的动态 RF 变化。我们比较了在对照条件下短暂刺激期间 dLGN 神经元的 RF 中心宽度的动态变化，以及在视觉刺激和电 PBR 刺激联合呈现期间的变化。主要发现是 PBR 刺激使 RF 中心宽度的动态变化提前，使得不同的反应成分更早出现。与先前的研究一致，我们还发现 PBR 刺激增加了持续反应成分期间的放电率增益。然而，当中心宽度最小时，从瞬态到持续成分的过渡期间，这种增益的增加尤其强烈。结果表明，增加的调制性 PBR 输入不仅增加了膝状体皮质传递的增益，而且有助于更快的传递动力学。我们讨论了对可能影响视觉空间分辨率的影响。
