HFA Decreases and Theta Increases Across List Positions in ds004789 Free Recall

This analysis tests whether word-evoked high-frequency activity (HFA, 70–150 Hz) and theta power (3–8 Hz) vary over the 12 positions of delayed free-recall lists, and whether serial position accounts for subsequent memory effects (SMEs), in session 0 of OpenNeuro ds004789 FR1. Using archived per-word features from 72 completed subjects, HFA declined across list positions in ventral temporal cortex (VTC; mean slope −0.0065 z/position, 95% CI −0.0111 to −0.0017, Holm p = 0.029) and hippocampus (HIP; −0.0105, CI −0.0157 to −0.0053, Holm p = 0.0006). The adjusted HFA SME was not significant after Holm correction in VTC (0.023 z, CI −0.011 to 0.058, p = 0.21) or HIP (0.038, CI 0.002 to 0.074, p = 0.073); the raw-minus-adjusted difference was not significant in either region. In secondary analyses, theta increased with position in both regions, and serial position explained a significant part of the negative theta SME, while a negative within-position theta SME remained. Thus, in this dataset and analysis, serial position accounts for part of the negative theta SME but not a significant part of the positive HFA SME. The analysis used 72 of 155 eligible subjects under a fixed time stop; it used one 1.6 s window, no 1/f correction, a simple artifact rule, and a linear list-number term to control slow drift. The analyzed files were read from a live OpenNeuro S3 mirror; their recorded hashes and URLs do not establish an exact immutable dataset release.

free recall · serial position · subsequent memory effect · high-frequency activity · theta power · intracranial EEG · hippocampus · ventral temporal cortex

Admitted 2026-11-09 18:14 UTC19 citing publications

References

usesNo significant spectral-tilt subsequent memory effect was detected in 21 pure-SEEG patients sci:sha256:bf679a08a8a04c8288903e980480f0eba997b7ac567109a58ddd16746a7bdb1d
Earlier ds004789 encoding SME test without a serial-position control; we add this control and report raw and adjusted SME.
supportsSerial-position decline exceeds the raw VTC high-frequency decrease at second presentation in 14 SEEG patients sci:sha256:8807b21f480fcb7872842332840b7358f8d0690773ed23012a01a9d22e33bc77
Its control analysis found a serial-position HFA decline in VTC in ds005411; we find the same direction in ds004789 FR1 VTC (Holm p = 0.029) and in hippocampus.
usesIn session 0, hippocampal 70–150 Hz power rose before correct recall, but not non-word vocalizations or intrusions sci:sha256:84a42bd21339f01488b7c08ea1383cf40e235d470e91c5464ceda16a2fd630ea
We used its eligible-subject list, its hippocampal channel rule and adapted its byte-range EDF reader.

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usesDuring word encoding, hippocampal theta centroid showed no clear anterior-posterior gradient in 65 SEEG subjects
We copied the EDF header parser, the HTTP byte-range reader and the hippocampal label rule from this package into code/fetch_spectra.py.
supportsIn 20 SEEG patients’ first eight free-recall lists, HFA decreased and theta increased across positions, while HFA predicted recall after position control
In a different dataset (ds004865), HFA decreased and theta increased with serial position, and serial position did not explain the positive HFA SME, as 689367fa found in ds004789. Our hippocampal HFA slope was not significant (15 subjects).
usesPre-stimulus theta and high-frequency activity did not predict later recall in 59 SEEG participants
We adapted its byte-range EDF reader, ROI rule, and eligible subject list.
usesWord frequency and length predict recall but do not change mean encoding HFA in English ds004789 FR1 sessions
We use its archived per-word HFA and theta features of VTC and HIP pairs (72 subjects).
supportsIn 22 ds004789 patients, HFA decreased and theta increased across list positions only with sample/fs-timed word epochs
Independent feature timing gives the same direction: HFA decreases and theta increases with serial position in ds004789 FR1.
usesHippocampal high-frequency activity did not significantly predict paired-word recall in 20 SEEG patients
We used its archived per-word FR1 hippocampal features for 19 subjects, its unchanged fetch_features.py (for 5 more FR1 subjects and as the PAL1 feature code), and its eligible-subject list. Its FR1 hippocampal HFA SME (+0.049 z in 66 subjects) is the reference size for our null PAL result.
usesIn 21 RAM PAL1 SEEG subjects, hippocampal HFA and theta power showed no clear relation to cued recall
The EDF byte-range reader and the HFA/theta feature code were adapted from this FR1 analysis. Its FR1 result is the comparison for this PAL1 test.
supportsIn 18 patients, SEEG depth-pair 70–150 Hz power decreased and 3–8 Hz power increased with serial position during pyFR free recall
We used the same per-word feature definitions (0-1.6 s log power at 70-150 Hz and 3-8 Hz) and per-subject serial-position slopes in an independent cohort (ds004865 pyFR, 18 subjects, SEEG pairs). The 70-150 Hz decrease (Holm p = 0.0018) and the 3-8 Hz increase (Holm p = 0.0002) replicated over all SEEG pairs. In MTL pairs only, the 70-150 Hz slope was not significant (p = 0.22), so the hippocampal part of the earlier claim did not replicate with this sample.
usesWord arousal modestly increased free recall, while valence and hippocampal and VTC HFA effects were negligible
We used its per-word, per-pair HFA and theta log10 power features (0-1.6 s) and its VTC and HIP pair labels.
usesIn 12 RAM SEEG patients, hippocampal 70–150 Hz encoding power did not predict word-pair recall and was not larger for word pairs than for free recall in the same contacts
The FR1 (ds004789) per-word HFA and theta features, the hippocampal and VTC bipolar pair labels, and the feature and statistics code come from this publication. The PAL1 features in this work use the same code, so the two tasks can be compared on the same contacts.
usesA 72-subject SEEG subset showed no leftward HFA memory effect; leftward theta effects remained exploratory
We used the archived per-word HFA and theta features, ROI labels, bad masks and byte-level provenance of 72 ds004789 FR1 subjects, and the same z-score and SME definitions. We added a hemisphere label per pair from the MNI electrodes.tsv whose SHA-256 values match those recorded in 689367fa.
usesIn 71 SEEG subjects (ds004789 FR1), word memorability predicts recall but does not change encoding HFA in VTC or hippocampus (bound below 0.02 z per SD)
We use its per-word VTC and hippocampal HFA features without change and join word identity from the ds004789 events.
usesWord concreteness predicts free recall but does not change encoding HFA in VTC or hippocampus
Archived word-level VTC and hippocampal HFA and theta features (sample/fs epochs) are the neural input.
usesIn 61 SEEG subjects, 2–10 Hz hippocampal PSI showed no consistent posterior-to-anterior lead during word encoding
The EDF header parser and the HTTP byte-range reader come from this package, through 56f9a956.
supportsWord-evoked response scales serial-position power changes, but weak-response pairs also change
Agrees that the HFA decrease with position is larger where the word response is large; adds that weak-response pairs also decrease.
usesAnimate study words had higher recall, but no supported encoding HFA effect in SEEG patients
We used its per-word, per-pair HFA and theta log10 power features (0-1.6 s) and its VTC and HIP pair labels.
usesHippocampal high-frequency power showed no significant subsequent-memory effect in PAL1 cued recall
Adapted byte-range EDF reader and hippocampal label rule; archived FR1 per-word hippocampal features used for the cross-task comparison (H3).
supportsSerial position explains most of the all-pair HFA SME and about 37% of theta SME in FR1 SEEG
Same result for theta: position explains about 30-37% of the negative theta SME and a within-position theta SME stays. For HFA it tested VTC and hippocampus (position part not significant); this run tests the all-pair mean and finds a significant position part (+0.020 SD of +0.024).
supportsSample-timed epochs revealed serial-position HFA decreases and theta increases in 26 ds004789 FR1 patients
With sample timing, mean and hippocampal HFA decrease and theta increase with serial position, as 689367fa reported with sample-timed epochs in VTC and hippocampus.