Cognitive Workload 8-level arithmetic

This dataset was generated from LSL/XDF recordings. Converted to bids with instructions and code [presented here](https://github.com/LMBooth/QT-arithmetic_study/tree/main/conversion_package)

- Original recordings are stored under sourcedata/xdf/ as .xdf files (non-BIDS).
- EEG was converted to BrainVision format (.vhdr/.eeg/.vmrk) under each sub-*/eeg/.
- *_events.tsv was generated from marker streams and then aligned so onset is relative to the EEG start time.
- Marker streams include task markers (arithmetic-Markers) and acquisition dropout annotations (UoHDataOffsetStream); events include a marker_stream column and marker definitions are in task-arithmetic_events.json.
- Pupil Labs gaze/pupil data was exported from the XDF pupil_capture stream into sub-*/eeg/ as eyetrack physio files (*_recording-eyetrack_physio.tsv.gz + *_recording-eyetrack_physio.json; PhysioType=eyetrack).
- ECG is captured on the EEG system; the ECG channel is typed in *_channels.tsv and exported as *_recording-ecg_physio.tsv.gz + *_recording-ecg_physio.json.
- ML analysis note: participants excluded from the ML analysis remain in participants.tsv with analysis_included=false; no epoch rejection was applied to this raw dataset.
- Participant IDs match the original XDF filenames; missing IDs correspond to excluded participants.

Participants
- N_recorded: 20
- N_released: 18
- Exclusions: 2 participants excluded due to multi-modal acquisition failures (sub-002, sub-017).
- Demographics in participants.tsv: age (years), sex, handedness.
- Excluded IDs remain in participants.tsv with analysis_included=false.

Hardware and data collection
- Combined EEG+ECG mobile EEG system (Bateson and Asghar, 2021; Clewett et al., 2016) and Pupil Labs Pupil Core, synchronized via Lab Streaming Layer (LSL).
- EEG: 19-channel 10-20 montage (Fp1, Fp2, F7, F3, Fz, F4, F8, T3, C3, Cz, C4, T4, T5, P3, Pz, P4, T6, O1, O2), Ag/AgCl electrodes with linked-ear reference, 250 Hz; impedances checked and Neurgel EEG gel applied.
- ECG: 3-lead on the same system; positive lead right shoulder/clavicle, negative lead left shoulder/clavicle, feedback lead lower left torso.
- Pupillometry: Pupil Labs Pupil Core eye tracking with infrared illuminators; LSL relay with asynchronous sampling (timestamps per sample).

Protocol summary
- Arithmetic task difficulty was defined using Q-value ranges and randomized order across trials.
- Task events encode difficulty in `trial_type` and `difficulty_range` (e.g.,baseline, 0.6-1.5, 1.5-2.4, ..., 6.0-6.9).
- Baseline for 60 seconds and then 70 questions, 10 at each difficulty level presented for 6 seconds each.
Task: arithmetic

Release notes
- Recorded 20 participants; released 18.
- Reason: multi-modal acquisition QC failure.
- Participant IDs match original XDF filenames; missing IDs indicate excluded participants.

References
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Appelhoff, S., Sanderson, M., Brooks, T., Vliet, M., Quentin, R., Holdgraf, C., Chaumon, M., Mikulan, E., Tavabi, K., Höchenberger, R., Welke, D., Brunner, C., Rockhill, A., Larson, E., Gramfort, A. and Jas, M. (2019). MNE-BIDS: Organizing electrophysiological data into the BIDS format and facilitating their analysis. Journal of Open Source Software 4: (1896).https://doi.org/10.21105/joss.01896

Pernet, C. R., Appelhoff, S., Gorgolewski, K. J., Flandin, G., Phillips, C., Delorme, A., Oostenveld, R. (2019). EEG-BIDS, an extension to the brain imaging data structure for electroencephalography. Scientific Data, 6, 103.https://doi.org/10.1038/s41597-019-0104-8

Clewett CJ, Langley P, Bateson AD et al (2016) Non-invasive, home-based electroencephalography hypoglycaemia warning system for personal monitoring using skin surface electrodes: a single-case feasibility study. Healthc Technol Lett 3:2-5. https://doi.org/10.1049/htl.2015.0037

Bateson AD, Asghar AUR (2021) Development and evaluation of a smartphone-based electroencephalography (EEG) system. IEEE Access. https://doi.org/10.1109/ACCESS.2021.3079992