Emergence from sedation involves an increase in both the level of consciousness and arousal.
Some insight to the neural core of consciousness was gained in the recent past. Our research
objective is to characterize for the first time the spatiotemporal mobilization of the
ascending reticular activating system during emergence from sedation; stated otherwise - to
capture the neural core of arousal.
To achieve this objective we plan to utilize the advanced imaging modality of EEG-fMRI. In
short, volunteers will be placed in the MRI. Following baseline recordings they will be
sedated with a continuous drip of propofol, titrated to deep sedation. Once in that sedation
level, propofol administration will cease until emerging to an awake-calm/light sedation.
Continuous EEG recordings and fMRI scans will be taken, both task specific (auditory oddball)
and resting-fMRI. Analyses will focus (but will not be restricted to) on constituents of the
ascending reticular activating system.
The expected advances of this proposal are:
1. Emergence from sedation (and anesthesia) is one of the critical stages and least
elucidated area in the practice of anesthesia. Delayed awakening of varying degree is
not uncommon after anesthesia and may have a number of different causes, individual or
combined, which may be both drug or non-drug related, thus causing a diagnostic dilemma.
Eventually - better insight into this subject will lead to better clinical practice and
better understanding why patients emerge in such a diverse and sometimes unexpected
manner.
2. Knowledge of the internal structure underlying arousal from anesthesia will help develop
/ upgrade brain monitors that could tell the anesthesiologist the patient's level of
consciousness and prediction of arousal.
3. A detailed reproducible mapping of the arousal process may serve as the core of a drug
screening platform for drugs that may expedite patient arousal.
4. Elucidation of the arousal paradigm from sedation will enhance our knowledge of
physiological sleep.
Research hypothesis
Return of consciousness is a complex phenomenon comprising of interplay between the cortex
and deeper brain structures. We hypothesize that the activation signature is conserved and
similar between subjects. Furthermore, we hypothesize that inter-subject variability will
arise mainly in the time domain, as evident from the clinical observation of variable time to
emergence in different patients.