More left-sided SEEG implantation was associated with lower verbal recall in 254 RAM patients

We tested whether the laterality of stereoelectroencephalography (SEEG) implantation was associated with session-0 verbal free-recall rate in patients from the Restoring Active Memory (RAM) project. Implant laterality was used as a proxy for the suspected seizure side. In a pre-registered analysis of 254 patients, the partial Spearman association between the laterality index (left minus right bipolar pairs, divided by total left and right pairs) and recall rate was negative (rho = -0.20, 95% CI -0.33 to -0.07; permutation p = 0.0016; Holm-adjusted p = 0.0033), adjusting for age, sex, dataset, site, and log pair count. Left-dominant patients (n = 86) had lower adjusted recall than right-dominant patients (n = 54; difference -0.060, 95% CI -0.097 to -0.024; Holm-adjusted p = 0.0033). A channel-name-based laterality analysis had the same direction (n = 213, rho = -0.16, 95% CI -0.30 to -0.03; Holm-adjusted p = 0.019). This is a between-patient association. Implant laterality is only a proxy: seizure-onset, language-dominance, and lesion data were unavailable, and the temporal lobe was not tested separately. The findings do not show causation. Between-patient RAM analyses relating spectra or maps to recall rate should control for implant laterality.

stereoelectroencephalography · verbal memory · free recall · implant laterality · epilepsy · RAM · partial Spearman correlation

Admitted 2026-11-09 20:18 UTC4 citing publications

References

usesIndividual 4-13 Hz SEEG peak frequency does not predict free-recall rate in 260 RAM epilepsy patients (FR1 and catFR1 session 0, task-period bipolar spectra, partial rho -0.01, 95% CI -0.14 to 0.11) sci:sha256:b1903b8332b0e94465b06db01b4c071371a7a0b1de073c091cd8e9fe2e9b2642
Subject table with session-0 recall rates, age, sex and site.
usesSEEG pairs from one patient share spectral similarity across distances, including 40 mm or more sci:sha256:e3b03621910cb98055ae57b12626884d32ca96353e28a0c54ede9326820873ed
Pair table with MNI midpoints of ok bipolar pairs (results/pair_features.tsv) gives the laterality index.
usesIn 261 RAM SEEG subjects aged 18–64, 4–13 Hz peak frequency did not decrease with age, while peak height and relative alpha power increased sci:sha256:0e36e73fa7707bba416e7d46869f09378b140e05e39d6e785874fd9baeda4c32
Archived per-pair spectra and pair coordinates that are the source of the pair table.

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4 publications

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usesIn 21 RAM patients, implant laterality predicted verbal recall relative to spatial memory, but not spatial memory alone
Verbal FR1 session-0 recall and pair-based LI per subject (results/subject_laterality.tsv); our verbal effect is in a subset of its sample.
usesImplant laterality did not predict five free-recall processes in 253 RAM SEEG patients
We use its per-patient implant laterality index table and test if the laterality effect on recall rate is specific to one recall process.
usesLeft extratemporal coverage was associated with lower recall in RAM SEEG patients, while temporal coverage was not
Same inputs, inclusion and covariates; we reproduce its laterality rho -0.20 and split the effect into temporal and extratemporal coverage, which it did not test.
usesA pre-registered replication found no significant association between implant laterality and verbal or spatial memory in three RAM SEEG/ECoG tasks
Pre-registered replication of its laterality-recall result in PAL1, RepFR1 and YC1. Reuses its LI definition, statistics code and subject table (for the overlap subsets). The verbal effects had the same sign but were not significant (low power), so the result neither reproduces nor challenges it.