Although all frequency bands contributed significantly to the EEG-coherence ICA component related to the rs-fMRI component, an examination of Fig. 2, Fig. 3 show that coherence within the theta, alpha, and gamma bands contributed the most to the component. Gamma frequency oscillations and synchronization between neural groups have been proposed to underlie perceptual experience and cognition (Doesburg et al., 2009a, Doesburg et al., 2009b, von Stein and Sarnthein, 2000, Ward, 2003, Whitman et al., 2013). Gamma oscillations appear to combine activity of spatially localized groups of neurons (e.g., within visual cortex (Gray and Singer, 1989); within hippocampus (Colgin et al., 2009)). Increased gamma band synchrony between frontal and parietal regions has also been observed during recollection (Burgess, 2012). Our results mostly show lower gamma coherence in the LTAA compared to NSAC within left ipsilateral regions. It is unclear how a decrease in resting gamma coherence would manifest behaviorally, although it seems likely that it would degrade performance of a network. The relationship of decreased gamma to our rs-fMRI results suggests that lower gamma coherence contributes to the decreased appetitive drive RSS observed in LTAA.
