Department of Neurobiology, Weizmann Institute of Science, Rehovot 76100, Israel.
Laboratory of Behavioral and Cognitive Neuroscience, Stanford Human Intracranial Cognitive Electrophysiology Program, Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA 94305, USA.
Neuron. 2021 Sep 1;109(17):2767-2780.e5. doi: 10.1016/j.neuron.2021.06.020. Epub 2021 Jul 22.
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.
海马回波是由海马神经元集合产生的突出同步事件。迄今为止，回波主要与啮齿动物的导航记忆和人类的短期情景记忆有关。在这里，我们在人类海马体中发现了不同的回忆近期和遥远自传事件和语义事实时的回波活动模式。我们发现，与对照条件相比，报告回忆前的回波率显著增加。多个海马体部位的回波活动模式显示出对记忆类型的显著特异性。有趣的是，这些回波模式揭示了一个语义化维度，即与自传内容相关的模式随着记忆年龄的增长而变得与语义记忆相似。最后，新皮质中广泛分布的部位在回忆时表现出与回波相关的激活，最强的激活位于默认模式网络内。因此，我们的结果揭示了海马回波在协调涉及有意识回忆的大规模网络中海马-皮质通讯方面的关键作用。
