“…It is noteworthy that multiscale entropy (MSE) analysis (Costa et al, 2002 , 2005 ; Yang and Tsai, 2013 ; Courtiol et al, 2016 ) calculates a series of sample entropy over multiple time scales, which captures the temporal complexity characteristcs of time-series neural signals from microscopic to macroscopic aspects. Recently, MSE analysis has also been applied to brain signals (Heisz and McIntosh, 2013 ; Yang et al, 2013 ; Courtiol et al, 2016 ), pain (Sitges et al, 2010 ; Valencia et al, 2016 ; Liu Q. et al, 2017 ), and PDM studies (Kuo et al, 2017 ; Low et al, 2017 ). By applying MSE analysis on resting-state magnetoencephalography (MEG) signals acquired from PDMs during pain-free state, we observed a general loss of regional complexity in PDMs at brain regions related to chronic pain, including the limbic circuitry, default mode network, sensorimotor network, and salience network (Low et al, 2017 ).…”