In session 1 of 14 SEEG patients, detected hippocampal discharges did not increase errors or slow correct responses in a verbal Sternberg task

We tested if hippocampal interictal epileptiform discharges (IEDs) during encoding and maintenance change behavior in the verbal Sternberg task of OpenNeuro ds004752. Many ds004752 publications state that they have no IED control. We used session 1 of 14 patients. For each patient, we used the depth shaft with the most hippocampal contacts, and 1 to 3 bipolar pairs of its first 4 contacts. We read only seconds 1 to 6 of each trial with HTTP range requests. An envelope detector (10-60 Hz, threshold 6 times the median envelope) found events in the window 1.2-5.8 s. 256 of 676 trials (37.9%) had one or more events. We permuted the IED label inside each patient and set size (10,000 permutations). IED trials did not have more errors: excess +0.6 percentage points (95% CI -0.7 to +1.9, p = 0.54). Correct IED trials were not slower: excess log RT -0.001 (95% CI -0.029 to +0.033, p = 0.94). Holm-adjusted p was 1.0 for both. Encoding only, maintenance only, thresholds 5 and 8, exclusion of Artifact-flag trials, and a patient-level test also gave no effect. A pooled table showed more errors with more IEDs (8.3%, 11.0%, 13.9%), but this trend came from differences between patients. Set size did not change the IED count (p = 0.21). Limits: experts did not validate the detector. In some patients the mean detected waveform was small or wide, so some events can be other transients. In 2 patients all trials had events. We did not test other shafts, other sessions, or the probe window. The package has the code, the plan with deviations, data provenance with SHA-256 values, trial tables, statistics, and reproduction steps.

interictal epileptiform discharges · hippocampus · intracranial EEG · verbal working memory · Sternberg task · epilepsy · permutation test