Abstract :
[en] Background: Recent studies have been shown that functional connectivity of cerebral areas is not a static phenomenon, but
exhibits spontaneous fluctuations over time. There is evidence that fluctuating connectivity is an intrinsic phenomenon of
brain dynamics that persists during anesthesia. Lately, point process analysis applied on functional data has revealed that
much of the information regarding brain connectivity is contained in a fraction of critical time points of a resting state
dataset. In the present study we want to extend this methodology for the investigation of resting state fMRI spatial pattern
changes during propofol-induced modulation of consciousness, with the aim of extracting new insights on brain networks
consciousness-dependent fluctuations.
Methods: Resting-state fMRI volumes on 18 healthy subjects were acquired in four clinical states during propofol injection:
wakefulness, sedation, unconsciousness, and recovery. The dataset was reduced to a spatio-temporal point process by
selecting time points in the Posterior Cingulate Cortex (PCC) at which the signal is higher than a given threshold (i.e., BOLD
intensity above 1 standard deviation). Spatial clustering on the PCC time frames extracted was then performed (number of
clusters = 8), to obtain 8 different PCC co-activation patterns (CAPs) for each level of consciousness.
Results: The current analysis shows that the core of the PCC-CAPs throughout consciousness modulation seems to be
preserved. Nonetheless, this methodology enables to differentiate region-specific propofol-induced reductions in PCC-CAPs,
some of them already present in the functional connectivity literature (e.g., disconnections of the prefrontal cortex,
thalamus, auditory cortex), some others new (e.g., reduced co-activation in motor cortex and visual area).
Conclusion: In conclusion, our results indicate that the employed methodology can help in improving and refining the
characterization of local functional changes in the brain associated to propofol-induced modulation of consciousness.
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