“…While the test–rest approach is valid to prove the stability of results, especially in longitudinal studies, it is not the most suitable test to assess the impact of pre-processing on quantitative estimation when repeated measurements are not provided. In this context, a series of papers have been recently published in which the performances of machine learning approaches to classify the MWL level after different signal pre-processing pipelines were compared [ 36 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 ]. These works are focused only on the automatic classification accuracy, considering several features extracted from all the EEG frequency bands and electrode signals, e.g., ERP, as input to the algorithm, whereas any direct evaluation of the EEG features extracted is provided.…”