Protocol Twenty-eight medication-naïve patients diagnosed with attention-deficit/hyperactivity disorder (ADHD) and twenty-eight healthy control participants completed a Go/No-Go task (Sustained Attention to Response Task; SART) embedded with thought-probes (experience sampling) to assess different attentional states, including spontaneous and deliberate mind-wandering. During the experiment, participants’ brain activity was recorded using a 64-channel EEG system. Symptom severity was additionally assessed using the Adult ADHD Self-Report Scale (ASRS). This dataset was analyzed to investigate the influence of mind-wandering on behavioral performance and cognitive processes. Reaction time, reaction time variability, and commission errors (performance measures), along with P100, P3b, and CRN ERP components (electrophysiological measures), were compared between mind-wandering and on-task episodes, as well as between ADHD and control groups, within a 20-trial window preceding each probe. Behavioral task Participants completed the Sustained Attention to Response Task (SART; Robertson et al., 1997), a computerized Go/No-Go task in which single-digit numbers from 1 to 9 were randomly presented with an equivalent probability of appearance (1/9). Participants were instructed to press the response button whenever a digit appeared on the screen (Go trial), except for the digit 3, which required no response (No-Go trial). They were encouraged to be quick and accurate. A total of 810 trials (720 Go trials and 90 No-Go trials) were divided into 15 blocks of either 27, 54, or 81 trials. The whole task required approximately 40 minutes per participant. At the end of each block, a thought-probe of five questions was presented on the screen. The first question asked participants about their attentional state immediately before the probe. Three response options were possible: 1) on-task (OT); 2) spontaneous mind-wandering (MW-S) and 3) deliberate mind-wandering (MW-D). The subsequent four questions inquired regarding participants' level of motivation, boredom, fatigue and task difficulty by positioning on analog scales that ranged from "Lowest level = 0" to "Highest level = 100." Electroencephalography The EEG was recorded with the BioSemi ActiveTwo System (Amsterdam, Netherlands) using a montage of 64 active electrodes, following the international 10-20 standard system. Two additional electrodes - a common mode sense (CMS) active electrode and a driven right leg (DRL) passive electrode placed on the nape - served mainly as reference and ground electrodes. The signal was acquired at a sampling rate of 2048 Hz with line noise at 50 Hz. The electrooculography (EOG) was recorded by two electrodes placed at the outer canthi of the eyes and two electrodes placed above and below the right eye. Two supplementary reference electrodes were attached to the earlobes. Dataset Description The ATTLAPSE_SART_EEG dataset was created by Gabriela Horáková, Sébastien Weibel, Ugo Tissot, Bich-Thuy Pham, Madalina Elena Costache, and Anne Bonnefond and conforms to BIDS version 1.9.0. This report was generated with MNE-BIDS (Appelhoff et al., 2019). The dataset consists of 56 participants (comprised of 27 male and 29 female participants; comprised of 47 right hand, 3 left hand and 6 ambidextrous; ages ranged from 18.0 to 59.0 (mean = 32.66, std = 11.32)) . Data was recorded using an EEG system (Brain Products) sampled at 512.0 Hz with line noise at 50.0 Hz. There were 56 scans in total. Recording durations ranged from 2266.0 to 2961.0 seconds (mean = 2508.55, std = 147.88), for a total of 140478.89 seconds of data recorded over all scans. Structure This dataset has been formatted with MNE-BIDS (Appelhoff et al., 2019) and is compliant with the BIDS format. It is composed of two sub-datasets, one for the raw/unprocessed data (EEG and behavior), and one for the preprocessed data (EEG and behavior). The phenotype directory gather the scores of a questionnaire, the ASRS, and the socio-demographic data of the subjects. NB: due to the limitation of volume storage, both raw and preprocessed EEG recordings (for each subject) had been resampled offline at 512 Hz. ├ derivatives: preprocessed EEG and behavioral data at the subject level│ ├ sub-{subject_id}│ │ ├ beh│ │ │ ├ sub-{subject_id}_task-sart_desc-preprocessed_beh.json: preprocessed behavioral data description│ │ │ └ sub-{subject_id}_task-sart_desc-preprocessed_beh.tsv: preprocessed behavioral data │ │ ├ eeg│ │ │ ├ sub-{subject_id}_task-sart_desc-preprocessed_channels.tsv: name and types of channels (64 EEG, 2 EXT [earlobes], 4 EOG, 2 EMG, 1 triggers)│ │ │ ├ sub-{subject_id}_task-sart_desc-preprocessed_eeg.eeg: preprocessed EEG signal (BrainVision format)│ │ │ ├ sub-{subject_id}_task-sart_desc-preprocessed_eeg.json: EEG acquisition main information│ │ │ ├ sub-{subject_id}_task-sart_desc-preprocessed_eeg.vhdr: preprocessed EEG metadata (BrainVision format)│ │ │ ├ sub-{subject_id}_task-sart_desc-preprocessed_eeg.vmrk: preprocessed EEG triggers (BrainVision format)│ │ │ ├ sub-{subject_id}_task-sart_desc-preprocessed_events.json: triggers description│ │ │ └ sub-{subject_id}_task-sart_desc-preprocessed_events.tsv: triggers│ │ └ sub-{subject_id}_scans.tsv: date and time of the EEG acquisition│ ├ BIDS_summary.txt: dataset summary and directory tree│ ├ dataset_description.json: dataset main characteristics│ └ README.txt: BIDS references├ phenotype│ ├ ASRS.json: ASRS scores description│ ├ ASRS.tsv: subjects scores at each item of the Adult ADHD Self-Report Scale (ASRS)│ ├ demographic.json: socio-demographic data description│ └ demographic.tsv: socio-demographic data of the cohort (anonymized ID, age, sex, handedness, number of education years└ sourcedata : raw (unprocessed) EEG and behavioral data at the subject level ├ sub-{subject_id} │ ├ beh │ │ ├ sub-{subject_id}_task-sart_beh.json: raw behavioral data description │ │ └ sub-{subject_id}_task-sart_beh.tsv: raw behavioral data (each line is a trial) │ ├ eeg │ │ ├ sub-{subject_id}_task-sart_channels.tsv: name and types of channels (64 EEG, 2 EXT [earlobes], 4 EOG, 2 EMG, 1 triggers) │ │ ├ sub-{subject_id}_task-sart_eeg.eeg: raw EEG signal (BrainVision format) │ │ ├ sub-{subject_id}_task-sart_eeg.json: EEG acquisition main information │ │ ├ sub-{subject_id}_task-sart_eeg.vhdr: raw EEG metadata (BrainVision format) │ │ ├ sub-{subject_id}_task-sart_eeg.vmrk: raw EEG triggers (BrainVision format) │ │ ├ sub-{subject_id}_task-sart_events.json: triggers description │ │ └ sub-{subject_id}_task-sart_events.tsv: triggers │ └ sub-{subject_id}_scans.tsv: date and time of the EEG acquisition ├ BIDS_summary.txt: dataset summary and directory tree ├ dataset_description.json: dataset main characteristics └ README.txt: BIDS references Contact Corresponding Author: Gabriela Horáková (gabriela@horakovci.eu)