Acticap slim

The EEG recording was performed using a 64 channel ActiCap Slim (Brain Products©). Electrode wires were gathered in two sets of 32 bundles through splitter boxes then routed to two standard BrainAmp amplifiers (Brain Vision Solutions©). The signal was digitized through a USB 2 adapter connected to the amplifiers then recorded at the computer using Brain vision recorder at a 1000 Hz sampling rate. Participants were comfortably seated on a chair with their back to the EEG installation. Auditory stimuli were presented using Psyscope XB77 software. Sounds were transmitted through audio speakers placed bilaterally, approximately 25 cm from their ears, with sound volume set at 65. During the procedure, participants watched a silent movie to facilitate collaboration and avoid movement artefacts as much as possible.
The task was similar to the one used by Ethridge and colleagues [42 (link), 43 (link)] where an auditory chirp stimulus made of a pure tone (1000 Hz) which amplitude was modulated by a sinusoid increasing linearly in frequency from 0 to 120 Hz over 2000 ms was presented 160 times, with ISI varying randomly between 1500 and 2500 ms.

A total of thirty healthy subjects were recruited (15 males and 15 females, 29 are right-handed; aged 24.26 ± 3.46 years). All subjects declared no history of stroke or other brain diseases. The experiment was approved by Westlake University Ethics Committee (approval ID: 20191023swan001). EEG signals of MI, ME, and GMI were recorded during six motions: right-hand finger tapping, left-hand finger tapping, holding a pen, opening a pen, crossing fingers, and moving an arm. Each task included five trials under three motor conditions (ME, MI, GMI). In MI tasks, subjects were instructed to imagine themselves doing the motion without any muscle activities with audio stimuli. In GMI tasks, the screen shows a picture of a specific motion, and subjects were instructed to conduct MI tasks with visual guidance.
EEG data were collected with 32 Ag/AgCl electrodes, a ground electrode, and a reference electrode, arranged in accordance with the 10–20 international standard. The EEG recording system consisted of the Brain Products actiCHamp Plus (EEG signal amplifier) and actiCAP slim (active EEG electrodes). More details of the recording system of the EEG signals and the experimental protocol can be found in our former work [5 (link)]. The dataset of this manuscript and our former work is the same.

The EEG system examined in this study was the Brain Products actiCHamp Plus (EEG signal amplifier) and actiCAP slim (active EEG electrodes) provided by Brain Products GmbH, Munich, Germany, as shown in Figure 3. Thirty-two active electrodes including a reference electrode and a ground electrode were introduced to the system. These electrodes can be placed onto three fabric caps (54–56 cm, 56–58 cm, or 58–60 cm), catering for participants’ head circumstances. A chin belt was attached to each cap to achieve better fixation and maintain electrodes’ position on the scalp. In total, 32 possible electrode positions arranged under a 10–20 international standard system were marked on each cap.
Before each experiment, a disinfectant wipe was applied to the electrodes. When finished, electrodes and caps were carefully cleaned from gels. These practices can effectively prevent crosstalk between channels induced by resting gels and enhance connectivity by removing dust and particles within the system.