“…A speculative hypothesis then is that the DMN operates in theta mode (which is reflected in the scalp EEG by an increase in frontal theta) when it becomes less active (i.e., during engagement in a task). This would not only explain the observed BOLD decreases during engagement in a task Raichle et al, 2001), but it would also explain why frontal theta power has been shown to increase in a wide range of cognitive tasks, such as mental arithmetic Burgess and Gruzelier, 1997;Inanaga, 1998;Inouye et al, 1994;Iramina et al, 1996;Ishihara and Yoshii, 1972;Ishii et al, 1999;Lazarev, 1998;Mizuki et al, 1980;Sasaki et al, 1996;Smith et al, 1999), error detection tasks (Luu et al, 2003;Luu et al, 2004), language comprehension tasks (Bastiaansen et al, 2002;Hald et al, 2006) and working memory tasks (Gevins et al, 1997;Jensen and Tesche, 2002;Krause et al, 2000;Onton et al, 2005). However, although this suggestion would account for the observed pattern of theta power increases, it appears to contradict several previous functional interpretations that increased frontal theta oscillations reflect synchronous activity in brain regions that are involved in cognitively demanding tasks (Inanaga, 1998;Ishihara and Yoshii, 1972;Jensen and Tesche, 2002;Laukka et al, 1995;Onton et al, 2005;Smith et al, 1999).…”