The evidence

Last updated 14 September 2026

The EEG trace, the spectrogram, the spectral edge and the index are all generated by a model, and every behaviour of that model is drawn from the published work listed below. The papers set the direction and the ordering of every effect; the absolute magnitudes on screen are teaching values, calibrated by eye against reference spectrograms and real monitor captures. The model's own numbers are not published; the sources they are calibrated to are, and each entry links to the open-access text where one exists. The model represents adult patients; paediatric EEG, which changes markedly with age, is outside its scope.

Corrections, feedback and suggested reading are gratefully accepted via contact@brainwaveneurosim.com.

The anaesthetic EEG

The awake reference, and the frontal signatures of the GABAergic agents.

  1. Purdon PL, Sampson A, Pavone KJ, Brown EN. Clinical electroencephalography for anesthesiologists: Part I: background and basic signatures. Anesthesiology. 2015;123(4):937–960. PMC4573341
  2. Brown EN, Lydic R, Schiff ND. General anesthesia, sleep, and coma. N Engl J Med. 2010;363(27):2638–2650. PMC3162622
  3. Kim MC, Fricchione GL, Brown EN, Akeju O. Role of electroencephalogram oscillations and the spectrogram in monitoring anaesthesia. BJA Educ. 2020;20(5):166–172. PMC7807831
  4. Purdon PL, Pierce ET, Mukamel EA, et al. Electroencephalogram signatures of loss and recovery of consciousness from propofol. Proc Natl Acad Sci U S A. 2013;110(12):E1142–E1151. PMC3607036
  5. Mogianos K, Persson AKM. Anesthesia depth monitoring during opioid free anesthesia – a prospective observational study. BMC Anesthesiol. 2025;25:37. PMC11761756

Propofol and sevoflurane dosing

The clinical doses each step of the propofol and sevoflurane controls is anchored to.

  1. Eleveld DJ, Colin P, Absalom AR, Struys MMRF. Pharmacokinetic–pharmacodynamic model for propofol for broad application in anaesthesia and sedation. Br J Anaesth. 2018;120(5):942–959. doi:10.1016/j.bja.2018.01.018
  2. Yang N, Zuo MZ, Yue Y, et al. Comparison of C50 for propofol–remifentanil target-controlled infusion and bispectral index at loss of consciousness and response to painful stimulus in elderly and young patients. Chin Med J (Engl). 2015;128(15):1994–1999. PMC4717953
  3. Nickalls RWD, Mapleson WW. Age-related iso-MAC charts for isoflurane, sevoflurane and desflurane in man. Br J Anaesth. 2003;91(2):170–174. doi:10.1093/bja/aeg132
  4. Fragen RJ, Dunn KL. The minimum alveolar concentration (MAC) of sevoflurane with and without nitrous oxide in elderly versus young adults. J Clin Anesth. 1996;8(5):352–356. PMID 8832444

Dexmedetomidine

The sleep-like spindle-over-slow-wave pattern, its depth dependence, and the infusion rates the steps are anchored to.

  1. Akeju O, Pavone KJ, Westover MB, et al. A comparison of propofol- and dexmedetomidine-induced electroencephalogram dynamics using spectral and coherence analysis. Anesthesiology. 2014;121(5):978–989. PMC4304638
  2. Xi C, Sun S, Pan C, et al. Different effects of propofol and dexmedetomidine sedation on electroencephalogram patterns: wakefulness, moderate sedation, deep sedation and recovery. PLoS One. 2018;13(6):e0199120. PMC6007908
  3. Seo KH, Kim K, Lee SK, Cho J, Hong JH. Changes in electroencephalographic power and bicoherence spectra according to depth of dexmedetomidine sedation in patients undergoing spinal anesthesia. Int J Med Sci. 2021;18(10):2117–2127. PMC8040410
  4. Ramaswamy SM, Weerink MAS, Struys MMRF, Nagaraj SB. Dexmedetomidine-induced deep sedation mimics non-rapid eye movement stage 3 sleep: large-scale validation using machine learning. Sleep. 2021;44(2):zsaa167. PMC7879420
  5. Fujita Y, Inoue K, Sakamoto T, et al. A comparison between dosages and plasma concentrations of dexmedetomidine in clinically ill patients: a prospective, observational, cohort study in Japan. J Intensive Care. 2013;1(1):15. PMC4336125

Ketamine

The biphasic, theta-led dose response, the gamma burst, and what ketamine does to a propofol plane and to the monitor.

  1. Akeju O, Song AH, Hamilos AE, et al. Electroencephalogram signatures of ketamine anesthesia-induced unconsciousness. Clin Neurophysiol. 2016;127(6):2414–2422. PMC4871620
  2. Vlisides PE, Bel-Bahar T, Lee U, et al. Neurophysiologic correlates of ketamine sedation and anesthesia: a high-density electroencephalography study in healthy volunteers. Anesthesiology. 2017;127(1):58–69. PMC5478453
  3. Sleigh J, Pullon RM, Vlisides PE, Warnaby CE. Electroencephalographic slow wave dynamics and loss of behavioural responsiveness induced by ketamine in human volunteers. Br J Anaesth. 2019;123(5):592–600. PMC6871266
  4. Linassi F, Troyas C, Kreuzer M, et al. Effect of ketamine on the bispectral index, spectral edge frequency, and surgical pleth index during propofol–remifentanil anesthesia: an observational prospective trial. Anesth Analg. 2025;140(6):1276–1285. PMC12063679
  5. Tanaka R, Kaneko M, Takekoshi M, Tanaka S. Effect of the addition of a low-dose of ketamine to propofol anaesthesia on the phase–amplitude coupling features of an electroencephalogram. BJA Open. 2025. PMC12767687
  6. de la Salle S, Choueiry J, Shah D, et al. Effects of ketamine on resting-state EEG activity and their relationship to perceptual/dissociative symptoms in healthy humans. Front Pharmacol. 2016;7:348. PMC5037139
  7. Garwood IC, Chakravarty S, Donoghue J, et al. A hidden Markov model reliably characterizes ketamine-induced spectral dynamics in macaque local field potentials and human electroencephalograms. PLoS Comput Biol. 2021;17(8):e1009280. PMC8405019
  8. Chamadia S, Gitlin J, Mekonnen J, et al. Ketamine induces EEG oscillations that may aid anesthetic state but not dissociation monitoring. Clin Neurophysiol. 2021;132(12):3010–3018. PMC8629941

When agents combine

The response-surface approach and the direction of each pairwise interaction.

  1. Schumacher PM, Dossche J, Mortier EP, et al. Response surface modeling of the interaction between propofol and sevoflurane. Anesthesiology. 2009;111(4):790–804. doi:10.1097/ALN.0b013e3181b799ef
  2. Diz JC, et al. Analysis of pharmacodynamic interaction of sevoflurane and propofol on bispectral index during general anaesthesia using a response surface model. Br J Anaesth. 2010;104(6):733–739. doi:10.1093/bja/aeq081
  3. Fragen RJ, Fitzgerald PC. Effect of dexmedetomidine on the minimum alveolar concentration (MAC) of sevoflurane in adults age 55 to 70 years. J Clin Anesth. 1999;11(6):466–470. PMID 10526824
  4. Dutta S, Karol MD, Cohen T, Jones RM, Mant T. Effect of dexmedetomidine on propofol requirements in healthy subjects. J Pharm Sci. 2001;90(2):172–181. PMID 11169534
  5. Hendrickx JFA, Eger EI, Sonner JM, Shafer SL. Is synergy the rule? A review of anesthetic interactions producing hypnosis and immobility. Anesth Analg. 2008;107(2):494–506. doi:10.1213/ane.0b013e31817b859e

Age and frailty

How the anaesthetic EEG weakens, slows and suppresses more readily with age and comorbidity.

  1. Purdon PL, Pavone KJ, Akeju O, et al. The Ageing Brain: age-dependent changes in the electroencephalogram during propofol and sevoflurane general anaesthesia. Br J Anaesth. 2015;115(Suppl 1):i46–i57. PMC4501918
  2. Hight DF, Voss LJ, Garcia PS, Sleigh J. Changes in alpha frequency and power of the electroencephalogram during volatile-based general anesthesia. Front Syst Neurosci. 2017;11:36. PMC5446988
  3. Kratzer S, Schneider M, Obert DP, et al. Age-related EEG features of bursting activity during anesthetic-induced burst suppression. Front Syst Neurosci. 2020;14:599962. PMC7744408
  4. Fang PP, Shang ZX, Xu J, et al. Contribution of intraoperative electroencephalogram suppression to frailty-associated postoperative delirium: mediation analysis of a prospective surgical cohort. Br J Anaesth. 2023;130(2):e263–e271. doi:10.1016/j.bja.2022.11.002
  5. Schwerin S, Schneider G, Kreuzer M, Kratzer S. Impact of age on the occurrence of processed electroencephalographic burst suppression. Anesth Analg. 2024;139(5):1027–1037. doi:10.1213/ANE.0000000000007143

The aperiodic background

The broadband floor under the spectral peaks, its shape, and how it moves with depth and age.

  1. Leroy S, Major S, Bublitz V, Dreier JP, Koch S. Unveiling age-independent spectral markers of propofol-induced loss of consciousness by decomposing the electroencephalographic spectrum into its periodic and aperiodic components. Front Aging Neurosci. 2022;14:1076393. PMC9889977
  2. Widmann S, Ostertag J, Zinn S, et al. Aperiodic component of the electroencephalogram power spectrum reflects the hypnotic level of anaesthesia. Br J Anaesth. 2025;134(2):392–401. PMC11775845

Epileptiform activity

The morphology and timing of spikes, sharp waves, spike-and-wave and an evolving seizure.

  1. Kane N, Acharya J, Beniczky S, et al. A revised glossary of terms most commonly used by clinical electroencephalographers and updated proposal for the report format of the EEG findings. Revision 2017. Clin Neurophysiol Pract. 2017;2:170–185. PMC6123891
  2. Hirsch LJ, Fong MWK, Leitinger M, et al. American Clinical Neurophysiology Society's standardized critical care EEG terminology: 2021 version. J Clin Neurophysiol. 2021;38(1):1–29. PMC8135051
  3. Sadleir LG, Farrell K, Smith S, Connolly MB, Scheffer IE. Electroclinical features of absence seizures in childhood absence epilepsy. Neurology. 2006;67(3):413–418. doi:10.1212/01.wnl.0000228257.60184.82
  4. Schomer DL, Lopes da Silva FH, eds. Niedermeyer's Electroencephalography: Basic Principles, Clinical Applications, and Related Fields. 7th ed. New York: Oxford University Press; 2018.

Natural sleep

The scoring rules for each sleep stage on a frontal montage, sawtooth waves, and how sleep changes with age.

  1. American Academy of Sleep Medicine. The AASM Manual for the Scoring of Sleep and Associated Events: Rules, Terminology and Technical Specifications. Version 3. Darien, IL: American Academy of Sleep Medicine; 2023. aasm.org
  2. Mander BA, Winer JR, Walker MP. Sleep and human aging. Neuron. 2017;94(1):19–36. PMC5810920
  3. Campos-Beltrán D, Marshall L. Changes in sleep EEG with aging in humans and rodents. Pflügers Arch. 2021;473(5):841–851. PMC8076123
  4. Frauscher B, von Ellenrieder N, Dolezalova I, et al. Rapid eye movement sleep sawtooth waves are associated with widespread cortical activations. J Neurosci. 2020;40(46):8900–8912. PMC7659451

Muscle, artefact and the monitor

Scalp muscle and movement artefact, and the sedation monitor whose spectrogram layout, suppression and artefact marking the display follows.

  1. Muthukumaraswamy SD. High-frequency brain activity and muscle artifacts in MEG/EEG: a review and recommendations. Front Hum Neurosci. 2013;7:138. PMC3625857
  2. Masimo Corporation. SedLine® Sedation Monitor operator's manual. Density spectral array estimation, time base, suppression and artefact marking, and the asymmetry definition.

Agents not modelled

Cited for what the simulator deliberately leaves out as yet: there is no opioid, nitrous oxide or benzodiazepine, so a real opioid-based anaesthetic will not match the presets step for step.

  1. Pavone KJ, Akeju O, Sampson AL, et al. Nitrous oxide-induced slow and delta oscillations. Clin Neurophysiol. 2016;127(1):556–564. PMC4675698

The educational-use disclaimer sets out what follows from all of this: the simulator is a teaching tool, not a medical device, and nothing it displays is to be used for patient care.

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