EEG spatial filter and method
First Claim
1. A machine-implemented method for enhancing EEG or MEG information related to a selected behavioral activity in a subject, comprisingattaching to the subject, a two-dimensional array of at least about 16 sensors for recording EEG or MEG traces from the subject, where the sensors are spaced from one another a distance which is substantially no greater than one-half the shortest expected spatial wavelength which is related to the selected behavioral activity, and where the area of placement of the array is one in which signals related to the selected activity can be detected by each sensor in the array,recording test EEG or MEG traces by the sensors over a period in which the selected behavior is manifested,selecting a test time interval within the recording period when such activity is occurring;
- decomposing the recorded traces into a series of basis functions Bi, each of which represents a signal or clutter component which is present to various degrees in all of the traces recorded by the array sensors in the selected test interval,determining, for at least one signal basis function Bj that is related to the selected behavioral activity, an amplitude matrix Aj which represents the spatial pattern of amplitudes of that basis function, as measured by the individual sensors in the array, in the selected test interval, andrepresenting test signals Sa recorded during the test interval by the array of sensors in the form;
space="preserve" listing-type="equation">S.sub.a =Σ
.sub.j A.sub.j B.sub.j (basis functions).
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Accused Products
Abstract
Method and apparatus for producing enhanced EEG or MEG information related to a selected brain activity in a subject. The apparatus includes a two-dimensional array of at least about 16 sensors for recording EEG or MEG traces from the subject. Control and test traces recorded before and during an interval in which the brain activity is occurring, respectively, are each decomposed into a series of basis functions which may be analytic components such as temporal frequency components, generated by spectral decomposition of an ensemble average of the recorded traces, or principal components determined by principal component analysis. The control and test traces are then represented as a sum of the products of the individual basis functions times a spatial domain matrix which represents the spatial pattern of amplitudes of that basis function, as measured by the individual sensors in the array. The signals can be extracted by filtering spatially and/or temporally to remove basis function components which are not related to the selected brain activity (clutter), and to remove spatial frequencies inherent in the spatial domain matrices to optimize the contrast between control and and corresponding test matrices, for each selected basis function.
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Citations
18 Claims
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1. A machine-implemented method for enhancing EEG or MEG information related to a selected behavioral activity in a subject, comprising
attaching to the subject, a two-dimensional array of at least about 16 sensors for recording EEG or MEG traces from the subject, where the sensors are spaced from one another a distance which is substantially no greater than one-half the shortest expected spatial wavelength which is related to the selected behavioral activity, and where the area of placement of the array is one in which signals related to the selected activity can be detected by each sensor in the array, recording test EEG or MEG traces by the sensors over a period in which the selected behavior is manifested, selecting a test time interval within the recording period when such activity is occurring; -
decomposing the recorded traces into a series of basis functions Bi, each of which represents a signal or clutter component which is present to various degrees in all of the traces recorded by the array sensors in the selected test interval, determining, for at least one signal basis function Bj that is related to the selected behavioral activity, an amplitude matrix Aj which represents the spatial pattern of amplitudes of that basis function, as measured by the individual sensors in the array, in the selected test interval, and representing test signals Sa recorded during the test interval by the array of sensors in the form;
space="preserve" listing-type="equation">S.sub.a =Σ
.sub.j A.sub.j B.sub.j (basis functions). - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A machine-implemented method for enhancing EEG or MEG information related to a selected brain activity in a subject, comprising:
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attaching to the subject, a two dimensional array of at least about 16 sensors for recording EEG or MEG traces from the subject, where the sensors are spaced from one another a distance which is substantially no greater than one-half the shortest expected spatial wavelength which is related to the selected behavioral activity, and where the area of placement of the array is one in which signals related to the selected event can be detected by each sensor in the array, recording control and test EEG or MEG traces by the sensors during control and test time intervals, respectively, which occur before and during such selected brain activity, respectively, decomposing the recorded test and control signals into a series of basis functions Bi and B'"'"'i, respectively, each of which represents a signal or clutter component which is present to various degrees in the test and control traces, respectively, recorded by the array sensors in the selected test or control intervals, determining, for each Bi and corresponding B'"'"'i basis function , an Ai and Ci amplitude matrix, respectively, which represents the spatial pattern of amplitudes of the associated basis function, as measured by the individual sensors in the array during the test and control intervals, respectively, selecting from among the basis functions Bi, those signal basis functions Bj for which the associated amplitude matrix Aj shows a statistically meaningful variance with the corresponding amplitude matrix Cj. representing test signals Sa recorded by the sensors in the form;
space="preserve" listing-type="equation">S.sub.a =Σ
.sub.j A.sub.j B.sub.j (basis functions). - View Dependent Claims (14)
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15. An apparatus for providing enhanced EEG or MEG information related to a selected behavioral activity in a subject, comprising:
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a two-dimensional array of at least about 16 sensors for recording EEG or MEG traces from the subject, where the sensors are spaced from one another by a distance which is substantially no greater than one-half the shortest expected spatial wavelength which is related to the selected behavioral activity, and where the area of placement of the array is one in which signals related to the selected event can be detected by each sensor in the array, means for recording test EEG or MEG traces by the sensors during a test interval in which the selected brain activity is occurring, and means for filtering the recorded traces to remove clutter components which are unrelated to such behavioral activity, said filtering means including means for decomposing the test traces into a series of basis functions Bi, each of which represents a signal or clutter component which is present to various degrees in all of the signals recorded by the array sensors in the test interval, and means for determining, for at least one signal basis function Bj that is related to the selected brain activity, an amplitude matrix Aj which represents the spatial pattern of amplitudes of that basis function, as measured by the individual sensors in the array, thereby to generate filtered signals recorded during the test interval by the array of-sensors in the form;
space="preserve" listing-type="equation">S.sub.a =Σ
.sub.j A.sub.j B.sub.j (basis functions). - View Dependent Claims (16, 17, 18)
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Specification