& Friston, 2003). Different frequencies of oscillations in turn are consistently associated with particular cognitive and perceptual states. The alpha rhythm, for example, originates in multiple thalamocortical projections (Lopes da Silva, Vos, Mooibroek, & Van Rotterdam, 1980), and it is typically observed during periods when an individual is relaxed but alert. It is most prominent when measured over the visual cortex in an individual with eyes closed; it thus appears to reflect an intrinsic rhythm that is greatest in amplitude in the absence of sensory load and in a state of inactivity (Goldman, Stern, Engel, & Cohen, 2002). It has been proposed that alpha activity (increased synchronization) serves a control function, inhibiting activity in particular neural circuits, which facilitates in turn the appropriate timing of cortical processes (Klimesch, Sauseng, & Hanslmayr, 2007) as well as protecting against intrusion by irrelevant information into selective attention and short-term memory (Foxe & Snyder, 2011; Payne, Guillory, & Sekuler, 2013).
