Hippocampal ripples are prominent synchronization events generated by hippocampal neuronal assemblies. To date, ripples have been primarily associated with navigational memory in rodents and short-term episodic recollections in humans. Here, we uncover different profiles of ripple activity in the human hippocampus during the retrieval of recent and remote autobiographical events and semantic facts. We found that the ripple rate increased significantly before reported recall compared to control conditions. Patterns of ripple activity across multiple hippocampal sites demonstrated remarkable specificity for memory type. Intriguingly, these ripple patterns revealed a semantization dimension, in which patterns associated with autobiographical contents become similar to those of semantic memory as a function of memory age. Finally, widely distributed sites across the neocortex exhibited ripple-coupled activations during recollection, with the strongest activation found within the default mode network. Our results thus reveal a key role for hippocampal ripples in orchestrating hippocampal-cortical communication across large-scale networks involved in conscious recollection.

海马涟漪是由海马神经元组装产生的显着同步事件。迄今为止，涟漪主要与啮齿动物的导航记忆和人类的短期情景回忆有关。在这里，我们揭示了在检索最近和远程自传事件和语义事实期间人类海马体中涟漪活动的不同特征。我们发现，与控制条件相比，在报告召回之前，涟漪率显着增加。跨多个海马位点的涟漪活动模式显示出对记忆类型的显着特异性。有趣的是，这些涟漪模式揭示了一个语义化维度，其中与自传内容相关的模式与作为记忆年龄函数的语义记忆的模式相似。最后，在回忆期间，新皮质中广泛分布的站点表现出波纹耦合激活，在默认模式网络中发现了最强的激活。因此，我们的研究结果揭示了海马涟漪在参与有意识回忆的大规模网络中协调海马 - 皮层通信中的关键作用。