The ability to recognize information that is incongruous with previous experience is critical for survival. Novelty signals have therefore evolved in the mammalian brain to enhance attention, perception and memory 1 , 2 . Although the importance of regions such as the ventral tegmental area 3 , 4 and locus coeruleus 5 in broadly signalling novelty is well-established, these diffuse monoaminergic transmitters have yet to be shown to convey specific information on the type of stimuli that drive them. Whether distinct types of novelty, such as contextual and social novelty, are differently processed and routed in the brain is unknown. Here we identify the supramammillary nucleus (SuM) as a novelty hub in the hypothalamus 6 . The SuM region is unique in that it not only responds broadly to novel stimuli, but also segregates and selectively routes different types of information to discrete cortical targets—the dentate gyrus and CA2 fields of the hippocampus—for the modulation of mnemonic processing. Using a new transgenic mouse line, SuM-Cre, we found that SuM neurons that project to the dentate gyrus are activated by contextual novelty, whereas the SuM–CA2 circuit is preferentially activated by novel social encounters. Circuit-based manipulation showed that divergent novelty channelling in these projections modifies hippocampal contextual or social memory. This content-specific routing of novelty signals represents a previously unknown mechanism that enables the hypothalamus to flexibly modulate select components of cognition. The supramammillary nucleus in the hypothalamus acts as a novelty hub that selectively directs different types of novelty signals to different subregions of the hippocampus and flexibly modulates the encoding of memory.

中文翻译：

---

下丘脑新奇信号调节海马记忆

识别与以往经验不一致的信息的能力对于生存至关重要。因此，新奇信号在哺乳动物大脑中进化，以增强注意力、感知和记忆 1, 2。尽管腹侧被盖区 3 、 4 和蓝斑 5 等区域在广泛的信号新颖性方面的重要性已经确立，但这些弥漫性单胺能发射器尚未显示出传达有关驱动它们的刺激类型的特定信息。不同类型的新奇事物，如上下文和社会新奇事物，是否在大脑中以不同的方式处理和路由尚不清楚。在这里，我们将乳头上核 (SuM) 确定为下丘脑 6 的新中心。SuM 区域的独特之处在于它不仅对新刺激做出广泛反应，但也将不同类型的信息隔离并有选择地路由到离散的皮层目标——海马的齿状回和 CA2 区域——以调节记忆处理。使用新的转基因小鼠品系 SuM-Cre，我们发现投射到齿状回的 SuM 神经元被上下文新奇激活，而 SuM-CA2 回路优先被新的社交接触激活。基于电路的操作表明，这些预测中不同的新奇通道会改变海马的上下文或社会记忆。这种新奇信号的特定内容路由代表了一种以前未知的机制，它使下丘脑能够灵活地调节认知的选择组件。