{"success":true,"database":"eegdash","data":{"_id":"6953f4249276ef1ee07a3375","dataset_id":"ds004642","associated_paper_doi":null,"authors":["Vasileios Dimakopoulos","Marian Neidert","Johannes Sarnthein"],"bids_version":"1.4.0","contact_info":["Vasileios S. Dimakopoulos","Johannes Sarnthein"],"contributing_labs":null,"data_processed":false,"dataset_doi":"doi:10.18112/openneuro.ds004642.v1.0.1","datatypes":["ieeg"],"demographics":{"subjects_count":10,"ages":[38,44,32,50,46,56,32,38,42,19],"age_min":19,"age_max":56,"age_mean":39.7,"species":null,"sex_distribution":{"f":6,"m":4},"handedness_distribution":null},"experimental_modalities":null,"external_links":{"source_url":"https://openneuro.org/datasets/ds004642","osf_url":null,"github_url":null,"paper_url":null},"funding":["Swiss National Science Foundation, SNSF 204651","Alexander S. Onassis Public Benefit Foundation Scholarship"],"ingestion_fingerprint":"74cd956f34bbacd8695f39390eb26bf7d403789de73c4930bff5b10b08170777","license":"CC0","n_contributing_labs":null,"name":"Intraoperative recordings of medianus stimulation with low and high impedance ECoG","readme":" ## Intraoperative recordings of medianus stimulation with low and high impedance ECoG\nThis dataset of medianus SEP was first analyzed in publication [1]. There we investigated whether the low impedance ECoG electrode (LoZ) improves fast ripple detection over a standard electrode with high impedance contacts (HiZ).\nThere are 10 patients (median age 40 y, range 19-56 y, 6 female) who underwent brain tumor resections in the perirolandic region at our institution. The data includes the continuous raw data from the ECoG contacts of both electrodes. We recorded medianus SEP intraoperatively (stimulation rate = 4.7 Hz) from two 4-contacts ECoG strips simultaneously (LoZ: a contacts, HiZ: b contacts) that had different median impedance (LoZ: 3.4 kΩ, HiZ: 6.9 kΩ).\n### Repository structure\n### Main directory (LoZ HFO)\nContains metadata files in the BIDS standard about the participants and the study. Folders are explained below.\n### Subfolders\n-   LoZ HFO/sub-/ Contains folders for each subject, named sub-  and session information.\n-   LoZ HFO/sub-/ses-01/ieeg/ Contains the raw ieeg data in .edf format for each subject. Each *ieeg.edf file contains continuous iEEG data from one stimulation rate recorded at the hand area Ω from both the electrodes simultaneously . Details about the channels are given in the corresponding .tsv file.\n### Note from the paper\n\"The offline data processing used the continuous ECoG that was recorded in parallel to the SEP recordings. Data analysis was performed with custom scripts in Matlab. To detect the SEP stimulation artefact, we first filtered the ECoG (high pass cutoff = 200 Hz) and performed local peak detection (minimum peak prominence between peaks = 30 ms, minimum peak width = 4 ms, samples = 0.2 ms). We used the times of the detected stimulus artifact as triggers to define sweeps with post-stimulus recording sweep length 50 ms. We classified sweeps with amplitude ±100 µV as artefact-ridden and excluded them from further analysis.\nWe averaged 100 sweeps and filtered the averaged trace (bandpass [30 300] Hz, IIR filter, response roll-off -12 db per octave, forward and reverse filtering to avoid phase distortion). We visually inspected the data and selected one optimal channel with high N20 amplitude (positive or negative) for further analysis. From the averaged N20 trace, we determined the N20 peak latency. To obtain the N20 peak amplitude and the SNR, we inspected the latency of the N20 peak. If the N20 latency was >20 ms, we selected a signal window [20 25] ms. If the N20 latency was ≤ 20 ms, we selected a signal window [17 22] ms. In the same way, we filtered the averaged trace in the [250 500] Hz band to obtain the evoked FR and in the [500 1000] Hz band to obtain the evoked HFO. We doubled the largest deflection in the signal window of the N20 frequency band to define the N20 signal amplitude. In the FR and HFO bands we used the peak-to-peak amplitude.\"\n### BIDS Conversion\nbids-starter-kid and custom Matlab scripts were used to convert the dataset into BIDS format.\n### References\n[1] Vasileios Dimakopoulos, Marian C. Neidert, Johannes Sarnthein, Low impedance electrodes improve detection of high frequency oscillations in the intracranial EEG, Clinical Neurophysiology, 2023, ISSN 1388-2457, https://doi.org/10.1016/j.clinph.2023.07.002\nIf you have any inquiries or questions, contact:\n* Vasileios Dimakopoulos (vasileios.dimakopoulos@usz.ch)\n* Johannes Sarnthein (johannes.sarnthein@usz.ch)","recording_modality":["ieeg"],"senior_author":"Johannes Sarnthein","sessions":["01"],"size_bytes":1292805561,"source":"openneuro","study_design":null,"study_domain":null,"tasks":["lozHFO"],"timestamps":{"digested_at":"2026-04-22T12:26:46.686249+00:00","dataset_created_at":"2023-07-17T13:57:44.780Z","dataset_modified_at":"2023-07-31T08:41:33.000Z"},"total_files":10,"storage":{"backend":"s3","base":"s3://openneuro.org/ds004642","raw_key":"dataset_description.json","dep_keys":["CHANGES","README","participants.json","participants.tsv"]},"tagger_meta":{"config_hash":"4a051be509a0e3d0","metadata_hash":"e2101ef152d5f08f","model":"openai/gpt-5.2","tagged_at":"2026-01-20T10:44:19.982292+00:00"},"tags":{"pathology":["Surgery"],"modality":["Other"],"type":["Other"],"confidence":{"pathology":0.85,"modality":0.8,"type":0.85},"reasoning":{"few_shot_analysis":"The closest few-shot match is the example titled \"Intraoperative EEG dataset during medianus-tibialis stimulation with 8 different rates\", which is labeled Pathology=Surgery, Modality=Other, Type=Other. It shares the same core paradigm and context: intraoperative recordings with medianus (median nerve) stimulation to elicit somatosensory evoked potentials (SEP), and analysis based on detecting stimulation artifacts and averaging sweeps. This example guides using Surgery for intraoperative SEP cohorts, and using Other (rather than Tactile/Perception) for the stimulus modality/type in these clinical neurophysiology monitoring paradigms.","metadata_analysis":"Key metadata facts:\n1) Intraoperative surgical cohort: \"There are 10 patients ... who underwent brain tumor resections in the perirolandic region\" and \"We recorded medianus SEP intraoperatively\".\n2) Somatosensory/nerve stimulation SEP paradigm with intracranial electrodes: \"This dataset of medianus SEP\" and \"stimulation rate = 4.7 Hz\" and \"continuous ECoG ... recorded in parallel to the SEP recordings\".\n3) Research aim is methodological/clinical signal detection: \"investigated whether the low impedance ECoG electrode (LoZ) improves fast ripple detection\" and the analysis describes extracting \"evoked FR\" and \"evoked HFO\" bands.","paper_abstract_analysis":"No useful paper information.","evidence_alignment_check":"Pathology:\n- Metadata says: \"10 patients ... underwent brain tumor resections\" and recordings are \"intraoperative\".\n- Few-shot pattern suggests: intraoperative SEP datasets are labeled as Surgery (see the intraoperative medianus/tibialis stimulation example).\n- Alignment: ALIGN (both indicate a surgical intraoperative patient cohort). Note: metadata also mentions \"brain tumor resections\" (could suggest Cancer), but the dataset framing is explicitly intraoperative.\n\nModality:\n- Metadata says: \"medianus stimulation\" / \"medianus SEP\" (peripheral nerve stimulation to evoke somatosensory potentials).\n- Few-shot pattern suggests: similar intraoperative SEP stimulation is labeled Modality=Other (rather than Tactile) in this catalog’s convention.\n- Alignment: PARTIAL ALIGN; metadata could support Tactile, but few-shot convention for intraoperative SEP favors Other. No explicit contradiction, just taxonomy convention.\n\nType:\n- Metadata says: goal is to test electrode impedance for better \"fast ripple detection\" / \"evoked ... HFO\" during SEP, i.e., a clinical-methods/neurophysiology focus rather than a cognitive construct.\n- Few-shot pattern suggests: intraoperative SEP stimulation datasets are labeled Type=Other.\n- Alignment: ALIGN (both indicate non-cognitive, clinical neurophysiology methodology rather than Perception/Attention/etc.).","decision_summary":"Top-2 candidates with head-to-head selection:\n\nPathology:\n- Surgery (selected): Supported by \"Intraoperative recordings\" and \"We recorded medianus SEP intraoperatively\" plus the close few-shot intraoperative SEP example labeled Surgery.\n- Cancer (runner-up): Supported by \"brain tumor resections\" (tumor patients), but the dataset is organized around intraoperative SEP/HFO methodology rather than tumor disease characterization.\nDecision: Surgery wins because recruitment/context is explicitly intraoperative surgical monitoring, matching the closest few-shot convention.\nConfidence basis: 2 explicit metadata quotes + strong few-shot analog.\n\nModality:\n- Other (selected): Few-shot intraoperative SEP example uses Other; this dataset is likewise intraoperative SEP with electrical nerve stimulation and iEEG/ECoG recording.\n- Tactile (runner-up): Reasonable from \"medianus stimulation\" / SEP as a somatosensory input, but not labeled that way in the closest catalog precedent.\nDecision: Other wins due to closest few-shot convention for intraoperative SEP datasets.\nConfidence basis: 1–2 explicit metadata indicators of SEP/medianus stimulation + strong few-shot analog.\n\nType:\n- Other (selected): Focus is methodological/clinical signal detection (\"low impedance ... improves fast ripple detection\", extracting \"evoked FR\"/\"evoked HFO\"), not a cognitive task.\n- Clinical/Intervention (runner-up): Plausible because it is patient intraoperative clinical recording, but the study aim is primarily methodological rather than an intervention/clinical outcome trial.\nDecision: Other wins consistent with the intraoperative SEP few-shot example and the explicitly methods-oriented aim.\nConfidence basis: 2 explicit metadata quotes about improving detection and HFO/FR extraction + strong few-shot analog."}},"nemar_citation_count":2,"computed_title":"Intraoperative recordings of medianus stimulation with low and high impedance ECoG","nchans_counts":[{"val":8,"count":7},{"val":9,"count":2},{"val":10,"count":1}],"sfreq_counts":[{"val":20000.0,"count":10}],"stats_computed_at":"2026-04-22T23:16:00.308127+00:00","total_duration_s":3849.7,"author_year":"Dimakopoulos2023_Intraoperative","canonical_name":null}}