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. 2024 Feb 16;27(3):587–599. doi: 10.1038/s41593-023-01550-x

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© The Author(s) 2024

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.

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Fig. 2 — a, Location of an example bipolar hippocampal channel (blue arrow). Blue circles, electrode contacts contributing to the bipolar channel; orange circles, other contacts. b, Probability distribution of all bipolar hippocampal channels, overlaid on the participants’ average MRI scan. c, MTL regions used for the recordings of LFPs and single-neuron activity. d, Illustration of the two innermost electrode contacts of an intracranial EEG macroelectrode with microelectrodes protruding from its tip. e, Analysis procedure for identifying ripples. Top to bottom: raw macroelectrode LFP; macroelectrode LFP filtered in the 80–140-Hz ripple band; smoothed envelope of the ripple band macroelectrode LFP; and spectrogram of the macroelectrode LFP. The power spectrum of each ripple event had to exhibit a global peak between 80 Hz and 140 Hz (white inset in bottom panel); otherwise, it was discarded as a false positive. f, Action potentials of two clusters from a microelectrode simultaneously recorded with the macroelectrode data. g, Raw voltage trace of an example hippocampal ripple (green) in the time domain (left) and its relative power spectrogram in the time–frequency domain (right). Time 0, ripple peak. h, Grand average voltage trace of hippocampal ripples across all channels in the time domain (left) and their power spectrogram in the time–frequency domain (right). Ripples were first averaged per channel and then across channels. Voltage traces are baseline corrected with respect to ±3 s around the ripple peak. Error bands, ±s.e.m. Ripple power is shown as the relative change with respect to the average power within ±3 s around the ripple peak. Time 0, ripple peak. i, Delta phase locking (0.5–2 Hz) of hippocampal ripples. Black histogram, ripple-associated delta phase for each channel. Gray histogram, delta phases of surrogate ripples. AMY, amygdala; EC, entorhinal cortex; HC, hippocampus; PHC, parahippocampal cortex; RC, relative change; RP, relative power; TP, temporal pole.