## 4 Materials  
Steady-state visually evoked potentials were chosen as an indicator for evaluating the quality of the artifact removal process. By examining SSVEP, one can determine whether the key signal components are preserved and become more pronounced following artifact removal. In this context, a dedicated experiment was designed in which volunteers were exposed to SSVEP while simultaneously inducing muscle artifacts. Recording SSVEP in the presence of artifacts enabled thorough testing of newly developed noise-reduction algorithms, with SSVEP serving as a reference standard. Jaw clenching was identified as the most disruptive artifact and was therefore recorded for data acquisition. Performing this artifact did not interfere with participants' ability to observe the LED, on which they focused to monitor SSVEP. Other considered artifacts--such as squinting, blinking, lateral eye movements, or cheek puffing--were found to disrupt the observation of the pulsating LED, thereby hindering the generation of SSVEP. Consequently, jaw clenching was chosen for this study. Although it is a strong artifact with a broad interference bandwidth, it does not impede perception of SSVEP. The electrodes used for data collection were selected based on earlier studies indicating the optimal configuration for recording both EEG and muscle artifacts. They included electrodes O1, O2, and Oz--associated with SSVEP--Cz and Fp1 (for EOG), and five EMG electrodes--HEOG, neck, cheek, nape, and jaw [20]. In total, nine electrodes were used in the study, along with a reference electrode attached to the participant's earlobe. Figure 1 presents the EEG/EMG electrode placement used during the recording. The EEG electrode montage (O1, O2, Oz, Cz, and Fp1) was selected with the primary goal of optimizing the recording of SSVEP responses, while also minimizing setup time and participant discomfort. Since the experiment focused specifically on visually evoked potentials, occipital electrodes (O1, O2, and Oz) were prioritized due to their proximity to the visual cortex, where SSVEP signals are strongest and most reliably detected. Electrode Cz was added to capture the potential spread of muscle artifacts into central areas, and Fp1 served to monitor basic ocular activity such as blinking or eye movements. This configuration provided sufficient spatial resolution for the purposes of the study while reducing the time required to apply electrodes, which was particularly important when working with multiple participants. It also allowed us to maintain a clean experimental design centered on SSVEP analysis, without unnecessary complexity in channel layout. To support the identification and tracking of muscle-related artifacts, additional EMG electrodes were placed on the participant's face and neck: HEOG, neck, cheek, nape, and jaw. These electrodes, applied using adhesive patches, enabled localized tracking of muscle activity and helped visualize the topographic distribution of non-neural interference. During the experiment, a g.Tec g.USBamp 2.0 bioelectrical signal amplifier, an EEG cap, and a set of active g.LADYBIRD electrodes were employed. The sampling rate was set to 256 Hz. Data acquisition took place in a specially designed setup featuring an LED diode that emitted stimuli to elicit SSVEP at predefined frequencies (5-30 Hz). Twenty-four volunteers aged 18-52 took part in the study. Each participant was informed about the procedure of the experiment both in written and oral form. After reviewing the provided information, each individual gave voluntary and informed written consent to participate in the study. Next, each participant wore an EEG cap with active electrodes (O1, O2, Oz, Cz, and Fp1) and EMG electrodes affixed to the face and neck (HEOG, neck, cheek, nape, and jaw) using adhesive patches. A conductive gel was applied between each electrode and the skin to ensure optimal signal conduction. A custom Matlab-based software facilitated precise data acquisition, processing, and visualization. To ensure high data quality, filtering was applied.