... Arousal levels in humans have generally been associated with EEG alpha activity (Bollimunta, Chen, Schroeder, & Ding, 2008;Bollimunta, Mo, Schroeder, & Ding, 2011;Cantero, Atienza, Gómez, & Salas, 1999a;Figueredo-Rodríguez, Del Río-Portilla, Sánchez-Romero, Pérez-Ortiz, & Corsi-Cabrera, 2009;Hasan & Broughton, 1994), which is defined as an EEG oscillation between 8.0 and 13.0 Hz with amplitude usually below 50 mV and localized over posterior regions of the head (Buzsaki, 2006;Niedermeyer, 2005;Shaw, 2003). Spontaneous alpha activity appears during wakefulness mainly with eyes closed and under conditions of relaxation and mental inactivity (Alvarez, Pascual-Marqui, & Valdes-Sosa, 1990;Brazier, 1968;Cantero et al., 1999a;Inouye, Shinosaki, Yagasaki, & Shimizu, 1986;Rodin & Rodin, 1995). However, there is evidence that increases in alpha band activity during sleep may be considered an indicator of arousal and cortical activation (American Sleep Disorders Association, 1992;Cantero, Atienza, Salas, & Gómez, 1999b;Figueredo-Rodríguez et al., 2009;Hasan & Broughton, 1994;Pivik & Harman, 1995;Tyson, Ogilvie, & Hunt, 1984). ...