Master of Science
Dr. J Bruce Morton
Dr. Adrian Owen
The transition from wakefulness to sleep is marked by changes in neurophysiology, suggesting that changes in consciousness might be accompanied by changes in functional network organization. Brain activity of 21 healthy participants was measured via simultaneous EEG-fMRI as participants transitioned from wakefulness into sleep. All fMRI volumes were ICA-decomposed, yielding 42 neurophysiological sources. Independent component time courses were used to estimate mean functional connectivity (FC) and dynamic FC using a sliding window technique. Windowed matrices were submitted to k-means clustering (k = 7, L2-norm). Mean FC in Wake and Stage-2 Sleep (S2S) were similar. Dynamic analysis revealed differences in temporal features of FC. Participants transitioned more between connectivity states (CSs) and spent less time across all CSs in Wake than in S2S. Four of the seven CSs differed in their frequencies. The current analysis suggests conventional FC analyses obscure features in FC that are observable on a finer temporal scale.
El-Baba, Mazen, "Dynamic Functional Connectivity Reveals Temporal Differences in Wake and Stage-2 Sleep" (2017). Electronic Thesis and Dissertation Repository. 4603.