Fig. 2: Experimental paradigm, recording sites, schematic, and results of single-regional decoding analysis.

A Each trial began with a 1 s fixation screen, followed by a 2 s presentation of four, six, or eight letters. After letters disappeared, there was a 3 s maintenance period with a black square shown. Participants responded whether a probe letter was part of the original set by pressing “IN” or “OUT”. B Channel locations of all participants included 91 channels in the hippocampus (Hipp; light red), 46 channels in the entorhinal cortex (EC; light blue), and 136 channels in the lateral temporal cortex (LTC; light green). The brain was visualized by the BrainNet Viewer toolbox (www.nitrc.org/projects/bnv/)⁴³. C We conducted binary classification (load 4 vs load 6, load 6 vs load 8). Time-frequency analysis was performed on each trial to obtain power spectra in the hippocampus, EC, and LTC. For each classification task, 70% of the data was used for training and 30% for testing with a linear SVM classifier. D The decoding accuracy for load 4 vs load 6 did not show significant differences among the hippocampus, EC, and LTC across all cross-validations (n = 100, two-sided permutation t test: EC vs hippocampus: p = 0.768; EC vs LTC: p = 0.379; LTC vs hippocampus: p = 0.690; see distribution with 150 iterations in Supplementary Fig. S1). The EC exhibited the highest decoding accuracy for load 6 vs load 8 (n = 100 cross-validations; two-sided permutation t test: all ps < 0.001). ***p < 0.001. E Differences in decoding accuracy between low-to-medium and medium-to-high load conditions were smallest in the EC (n = 100 cross-validations; two-sided permutation t test: hippocampus vs EC: p < 0.001; LTC vs EC: p = 0.005; hippocampus vs LTC: p = 0.047). *p < 0.05, **p < 0.01, ***p < 0.001. In the box plots shown in (D, E), the center line represents the median, and the edges of the box correspond to the lower and upper quartiles, respectively. The whiskers extend to the minimum and maximum data points at most 1.5 times the interquartile range. Source data are provided as a Source Data file.