Division of Molecular and Developmental Biology, National Institute of Genetics, 1111 Yata, Mishima, Shizuoka 411-8540, Japan.
Curr Biol. 2013 Feb 18;23(4):307-11. doi: 10.1016/j.cub.2012.12.040. Epub 2013 Jan 31.
To understand how the brain perceives the external world, it is desirable to observe neuronal activity in the brain in real time during perception. The zebrafish is a suitable model animal for fluorescence imaging studies to visualize neuronal activity because its body is transparent through the embryonic and larval stages. Imaging studies have been carried out to monitor neuronal activity in the larval spinal cord and brain using Ca(2+) indicator dyes and DNA-encoded Ca(2+) indicators, such as Cameleon, GFP-aequorin, and GCaMPs. However, temporal and spatial resolution and sensitivity of these tools are still limited, and imaging of brain activity during perception of a natural object has not yet been demonstrated. Here we demonstrate visualization of neuronal activity in the optic tectum of larval zebrafish by genetically expressing the new version of GCaMP. First, we demonstrate Ca(2+) transients in the tectum evoked by a moving spot on a display and identify direction-selective neurons. Second, we show tectal activity during perception of a natural object, a swimming paramecium, revealing a functional visuotopic map. Finally, we image the tectal responses of a free-swimming larval fish to a paramecium and thereby correlate neuronal activity in the brain with prey capture behavior.
为了了解大脑如何对外界进行感知，在感知过程中实时观察大脑中的神经元活动是很有必要的。斑马鱼是一种适合用于荧光成像研究的模式动物，可以可视化神经元活动，因为其胚胎和幼体阶段的身体是透明的。已经进行了成像研究，使用 Ca(2+)指示剂染料和 DNA 编码的 Ca(2+)指示剂（如 Cameleon、GFP-aequorin 和 GCaMPs）来监测幼体脊髓和大脑中的神经元活动。然而，这些工具的时间和空间分辨率和灵敏度仍然有限，并且尚未证明在感知自然物体时对大脑活动进行成像。在这里，我们通过遗传表达新版本的 GCaMP 来证明幼体斑马鱼视顶盖神经元活动的可视化。首先，我们证明了在显示器上移动的斑点诱发的视顶盖中的 Ca(2+)瞬变，并鉴定了方向选择性神经元。其次，我们展示了在感知自然物体（游动草履虫）时的视顶盖活动，揭示了功能上的视拓扑图。最后，我们对自由游动的幼体鱼的视顶盖反应进行成像，并将大脑中的神经元活动与捕食行为相关联。
