Abstract: Disclosed is a method of estimating an arousal state of a person, the method comprising: providing one or more measurements of a physiological or behavioural variable relevant to the arousal state of the person; and updating a nonlinear physiologically based time-dependent model of arousal using the one or more measurements of the physiological or behavioural variable, thereby estimating an augmented state vector of the model, wherein the estimated augmented state vector of the model includes the arousal state of the person and one or more parameters of the model.

Abstract: A method of fitting a proposed model for electro encephalography spectra to data derived from EEG recordings, the method comprising the steps of: (a) inputting at least one spectral trace of electroencephalographic measurements; (b) inputting a series of parameters associated with the proposed model; (c) applying a non-linear fitting algorithm to the at least one spectral trace and the at least one series of parameters, wherein the non-linear fitting model preferably can include a series of constraints associated with predetermined ones of the series of parameters so as to constrain the parameters in a predetermined range.