1. Schrödinger's cat: anaesthetised and not!
A. Proekt, M. Kelz 
British Journal of Anaesthesia 
Volume 120, Issue 3, Pages (March 2018)
DOI: /j.bja
Copyright © 2017 British Journal of Anaesthesia Terms and Conditions

2. Fig 1
Evidence For Neural Inertia. A. Pharmacologic evidence for hysteresis. Concentration-response curve for induction (red) and emergence (blue) given by the EC50 and the Hill slope estimated by Friedman and colleagues5 in wild-type mice for isoflurane. The shaded area is a measure of hysteresis. Note that the emergence curve is not merely a left-shifted version for induction (red dashed curve) but is also characterized by a shallower Hill slope. Also note that in the intermediate concentration range the animal can be either awake or anesthetized depending on its previous history. B. Genetic evidence of hysteresis. The hysteresis was quantified as area enclosed by the induction and emergence concentration-response curve in Drosophila (e.g. Figure 1A). Hysteresis normally observed in wild-type flies is abolished by a single gene mutation (sssP1). Restoration of the SLEEPLESS protein in neurones but not in glia restores hysteresis. Data replotted from Joiner and colleagues.11 C. Physiological evidence of hysteresis. A representative spectrogram of a cortical local field potential (LFP) recorded by Hudson and colleagues12 at a series of fixed isoflurane concentrations (top of the spectrogram). While anaesthetic concentration was monotonically decreased once an hour, the spectra of brain activity fluctuated abruptly in a quasi-cyclical fashion. Note the clear lack of correspondence between the spectrum of brain activity and anaesthetic concentration. D. Mathematical mechanisms of hysteresis. A diagram adapted from Steyn Ross and colleagues26 shows simulated steady-state membrane voltage as a function of anaesthetic concentration for a mean field model of cortex. Note that for intermediate concentration range the neurones have two steady-state membrane voltages. Thus, the behaviour of the system is dictated not by the anaesthetic concentration but by initial conditions (i.e. previous history). As a consequence of this bi-stability the model exhibits hysteresis. Concentrations at which transitions to and from the anaesthetized state occur are shown by red and blue arrows, respectively.
British Journal of Anaesthesia  , DOI: ( /j.bja )
Copyright © 2017 British Journal of Anaesthesia Terms and Conditions