BRAIN FUNCTION PARAMETER MEASUREMENT SYSTEM AND METHOD
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.
1 . A method of fitting a proposed model of electroencephalographic spectra to observed spectral data, the method comprising the steps of:
(a) inputting at least one spectral trace of electroencephalographic measurements;
(b) inputting a series of initial parameter values associated with the proposed model; and
(c) applying a non-linear fitting algorithm to said at least one spectral trace and said at least one series of parameters, wherein said non-linear fitting algorithm iteratively modifies parameter values to improve the quality of the fit, and includes a series of constraints associated with predetermined ones of said series of parameters so as to constrain the parameters in a predetermined range, and
(d) outputting the fitted parameters as a proposed model of the electroencephalographic spectra.
2 . A method as claimed in claim 1 wherein said non-linear fitting algorithm includes utilising a Levenberg-Marquardt type algorithm to fit the data to the algorithm.
3 . A method as claimed in claim 1 wherein the non-linear fitting algorithm includes a cost function which increases superlinearly once a constraint is passed.
4 . A method as claimed in claim 1 wherein said model includes a total subcortical signal, a corticothalamic feedback, an electromyogram component and a thalamic signal source.
5 . A method as claimed in claim 4 wherein the thalamus signal includes a specific or secondary relay component and a reticular component.
6 . A method as claimed in claim 1 wherein said constraint increases linearly whenever a constraint boundary is crossed.
7 . A method as claimed in claim 1 wherein said initial parameter values are determined by prior investigation of electroencephalographic spectra measurements.
8 . A method as claimed in claim 1 wherein said method is used to monitor the effects of a medical dose to provide a measure of one of diagnostic sensitivity and specificity, determination of disorder and subgroup, or treatment prediction and response.
9 . A method as claimed in claim 1 wherein the method is utilised to stimulate, modulate, and/or control brain activity and behaviour.
10 . A method as claimed in claim 1 wherein the derived parameters are utilised to provide information or assistance to a user.
11 . A method as claimed in claim 1 wherein said step (c) further includes the step of reducing the standard deviations of the observed spectral data in a predetermined frequency dependant manner.
12 . A system for fitting a proposed model of electroencephalographic spectra to observed spectral data, the system comprising:
an electroencephalographic measurement unit measuring a subjects electroencephalographic response and outputting a spectral trace thereof; and
a parameter modelling unit connected to said spectral trace and applying a nonlinear fitting algorithm to determine a series of parameter model values to output a quality of fit of parameter values to the spectral trace for a predetermined brain model.
13 . A system as claimed in claim 12 wherein said parameter modelling unit further includes a constraint unit which constrains predetermined ones of said series of parameter values to predetermined ranges
14 . A method as claimed in claim 1 wherein said step (c) further includes the step of applying the non-linear fitting algorithm multiple times with different initial parameter values and selecting a set of consensus final parameters from the multiple application of the non-linear fitting algorithm.
15 . A system as claimed in claim 12 wherein said model includes a total subcortical signal, a corticothalamic feedback, an electromyogram component and a thalamic signal source.
16 . A system as claimed in claim 15 wherein the thalamus signal includes a specific or secondary relay component and a reticular component.
17 . A system as claimed in claim 12 wherein said parameter modelling unit applies a frequency dependant attenuation of the standard deviations of the spectral trace.