Fig. 3: A spectral narrowband peak in peri-event PSDs guides ripple-positive channel selection in humans.
a TOP: CT image showing electrode contacts and T2 image overlaid with hippocampal subfield divisions delineated using ASHS62. Arrow: microwires. LEFT: Behnke-Fried hybrid electrodes. BOTTOM: Anatomical distribution of electrodes used in this study. Large circles: macro-contacts; small circles: microwire bundles. Blue: Channels with >60 Hz peaks in peri-event PSDs. b Average waveform, wavelet spectrogram and example LFP traces of automatically detected ripples from example CA1 (top) and DG (bottom) macroelectrodes, referenced to the nearest WM electrode. c Peri-event power spectral density (PSD) of macroelectrodes in (b). Spectral peaks were extracted from 1/f-corrected PSD (dotted lines), which demonstrates that the CA1 electrode displays a narrowband peak >60 Hz whereas the DG electrode does not. d TOP: Peak frequency distribution of all hippocampal macro-contacts (n = 20) demonstrates a bimodal distribution above and below 60 Hz. BOTTOM: Percentage of macroelectrodes with a > 60 Hz spectral peak. Most electrodes lacking a > 60 Hz peak did not show ripples. e Microwire selection in two patients followed the same criteria as with macroelectrodes. TOP: Detection channels were selected based on the >60 Hz spectral peak in peri-event PSDs. When multiple channels showed >60 Hz peak, the one with the strongest power was selected (green shade). BOTTOM: If no channels showed a > 60 Hz peak, the entire bundle was considered ripple negative. f Percentage of microwire bundles with and without a narrowband >60 Hz peak. a Created in BioRender. Maslarova, A. (2025) https://BioRender.com/u24k047. Source data are provided as a Source Data file.
