Alpha bands are involved in various cognitive processes (Klimesch, 1999; Grandy et al., 2013), and recently, the relationship between the alpha band and cognitive processes was investigated by dividing the alpha bands into lower and upper alpha bands. Specifically, lower-alpha bands play an important role in attention (Horschig et al., 2014), whereas upper alpha bands reportedly affect memory (Lebedev, 1994; Klimesch, 1997; Clark et al., 2004). The FC analysis of the lower and upper alpha bands in this study showed that the BD group exhibited stronger connections in some areas but weaker connections in other areas compared with the non-BD group.
