Fig. 2. A diagram of the stability of the modeled cortex as increasing concentrations of enflurane and isoflurane are applied. b shows a three-dimensional plot of the steady state excitatory neuronal soma potential. The dark shading and light shading denote stable (awake or anesthetized) and unstable (seizure) states, respectively. a shows a two-dimensional plan view of b . The trajectory of increasing concentrations (X = 1 minimum alveolar concentration50) of enflurane) is shown by the dashed line , and the trajectory of isoflurane is shown by the solid line .The insets show the (inverted) shape of the inhibitory postsynaptic potential (IPSP) at the points denoted by the square and diamond .