Laboratory of Sensory Cell Biology and Organogenesis, Centre de Regulació Genòmica, 08003 Barcelona, Spain.
J Neurosci. 2012 Feb 29;32(9):2976-87. doi: 10.1523/JNEUROSCI.5157-11.2012.
Spatially distributed sensory information is topographically mapped in the brain by point-to-point correspondence of connections between peripheral receptors and central target neurons. In fishes, for example, the axonal projections from the mechanosensory lateral line organize a somatotopic neural map. The lateral line provides hydrodynamic information for intricate behaviors such as navigation and prey detection. It also mediates fast startle reactions triggered by the Mauthner cell. However, it is not known how the lateralis neural map is built to subserve these contrasting behaviors. Here we reveal that birth order diversifies lateralis afferent neurons in the zebrafish. We demonstrate that early- and late-born lateralis afferents diverge along the main axes of the hindbrain to synapse with hundreds of second-order targets. However, early-born afferents projecting from primary neuromasts also assemble a separate map by converging on the lateral dendrite of the Mauthner cell, whereas projections from secondary neuromasts never make physical contact with the Mauthner cell. We also show that neuronal diversity and map topology occur normally in animals permanently deprived of mechanosensory activity. We conclude that neuronal birth order correlates with the assembly of neural submaps, whose combination is likely to govern appropriate behavioral reactions to the sensory context.
空间分布的感觉信息通过外周感受器和中枢靶神经元之间的连接点对点对应在大脑中进行拓扑映射。例如，鱼类的机械感觉侧线的轴突投射组织了一个躯体定位的神经图。侧线为复杂的行为（如导航和猎物探测）提供了水动力信息。它还介导了由 Mauthner 细胞触发的快速惊跳反应。然而，目前尚不清楚侧线神经图是如何构建以适应这些对比行为的。在这里，我们揭示了斑马鱼的出生顺序使侧线传入神经元多样化。我们证明，早期和晚期出生的侧线传入神经元沿着后脑的主要轴分化，与数百个二级靶标形成突触。然而，来自初级感觉毛的早期传入神经元也通过汇聚到 Mauthner 细胞的侧树突形成一个单独的图，而来自次级感觉毛的投射从不与 Mauthner 细胞进行物理接触。我们还表明，在永久性丧失机械感觉活动的动物中，神经元多样性和图拓扑结构正常发生。我们得出结论，神经元的出生顺序与神经子图的组装相关，其组合可能控制对感觉环境的适当行为反应。
