Fig. 1: Significant neuronal assembly identification during an episodic memory task.

A Schematic of the free recall task. Each displayed word the participant studies represents an “encoding event.” B Unit yield for each brain region included in the study. C Example denoised high-frequency signals from which we isolated unit activity (top rows) and local field potentials (bottom rows) for each brain region. Coloring follows the convention shown in (B). Numbers next to the region indicate the number of units isolated from each region and include neurons from all sessions (n = 307), not only those from which assemblies were identified (n = 203). D Example units from each of the high-frequency signals displayed in (C). E Expression strength of two example assemblies superimposed on the pertinent spike rasters for three example encoding events. Expression strength curves and spike rasters are colored to link them with the assemblies in (F). F Schematics of four example neuronal assemblies. The first two correspond to the data shown in (E). Each colored data point represents a neuron from that recording session. The further the data point from the circle’s center, the greater the contribution of that neuron to the assembly, with member neurons falling outside of the dashed-line circle. The color of each data point represents the region of the neuron, as outlined in (B). G Comparison of the number of assemblies identified against a null distribution obtained by shuffling the spike trains (permutation test, n = 1000 shuffles, p = 0.0009). H Average and individual recall fraction of recording sessions with identified assemblies (n = 15). ***p < 0.001. Source data are provided as a source data file.