Dose-related effect of sevoflurane sedation on higher control of eye movements and decision making  S.A.R. Nouraei, N. de Pennington, J.G. Jones, R.H.S. Carpenter  British Journal of Anaesthesia  Volume 91, Issue 2, Pages 175-183 (August 2003) DOI: 10.1093/bja/aeg158 Copyright © 2003 British Journal of Anaesthesia Terms and Conditions

Fig 1 The countermanding paradigm. In a control trial (top), at the start of the trial a fixation target (black square) is presented. The dotted circle represents the position of the subject's gaze. After a random delay, the target jumps unpredictably to the left or right, and the subject makes a saccade to track it after a delay, the saccadic latency. In a stop trial (below), fixation is followed by a target jump as in a control trial, but the fixation light reappears after a fixed period (the stop-signal delay), signalling to the subject that no saccade should be made. On some trials subjects successfully inhibit the saccade, on others they do not. British Journal of Anaesthesia 2003 91, 175-183DOI: (10.1093/bja/aeg158) Copyright © 2003 British Journal of Anaesthesia Terms and Conditions

Fig 2 Typical reciprobit plot of saccadic latency data from one subject (A) for control trials at four different sevoflurane doses. Cumulative histograms (i.e. plots of the proportion of trials on which a saccade has occurred by a particular time) are plotted on a probit scale as a function of reciprocal latency (using a reciprocal scale labelled for ease of interpretation with latencies rather than their reciprocals: longer latencies lie to the right). If the LATER model is correct, the data should then lie on a straight line. The lines are best-fit straight lines, subject to the constraint of parallelism. Note that the use of a probit scale tends to throw the tails of the distribution into prominence: the deviations at longer latencies in some cases are not statistically significant. British Journal of Anaesthesia 2003 91, 175-183DOI: (10.1093/bja/aeg158) Copyright © 2003 British Journal of Anaesthesia Terms and Conditions

Fig 3 Reciprocal median simple latency (±1 se) plotted as a function of sevoflurane dose (MAC) for each subject, with fitted regression lines. Note that the latency axes are chosen to be appropriate for each subject. British Journal of Anaesthesia 2003 91, 175-183DOI: (10.1093/bja/aeg158) Copyright © 2003 British Journal of Anaesthesia Terms and Conditions

Fig 4 Reciprocal median stop-signal reaction time (±1 se) plotted as a function of sevoflurane dose (MAC) for each subject, with fitted regression lines. Note that the SSRT axes are chosen to be appropriate for each subject. British Journal of Anaesthesia 2003 91, 175-183DOI: (10.1093/bja/aeg158) Copyright © 2003 British Journal of Anaesthesia Terms and Conditions

Fig 5 The LATER model. When reaction times are plotted as cumulative distributions on a probit scale as a function of the reciprocal of latency (a reciprobit plot), in general they are found to yield a straight line (a), implying that the reciprocal of latency is distributed as a Gaussian. The line intersects the P=50% ordinate at the median latency, and the t=infinity axis at a point I. This behaviour can be explained by a simple mechanism (the LATER model) in which a decision signal, S, initially at a level S0, rises linearly on presentation of a stimulus until it reaches a threshold, ST, at which point a response is initiated. On different trials, r varies randomly about a mean μ in a Gaussian manner, such that the distribution of latency is skewed (shaded area) and the reciprocal of latency is Gaussian, as observed. British Journal of Anaesthesia 2003 91, 175-183DOI: (10.1093/bja/aeg158) Copyright © 2003 British Journal of Anaesthesia Terms and Conditions