EEG signal analysis system

Claim 1

A method of processing an EEG signal to provide an indication of cerebral activity in response to an event, the method comprising: sampling the EEG signal to produce digital sample values representative of amplitude of the EEG signal as a function of time; providing a plurality of digitized waveforms which are based at least in part on the digital sample values, which have a first length, and each of which includes fill values surrounding the digital sample values derived from one of a plurality of epochs having different time relationships to the event, each epoch having a second length which is less than the first length; transforming each digitized waveform from a time domain to a frequency domain to produce a frequency spectrum corresponding to one of the plurality of epochs, each frequency spectrum having frequency components uniquely attributable to the digital sample values derived from its corresponding epoch; deriving a frequency value for each epoch based upon the frequency spectrum corresponding to that epoch; and providing an output indicative of cerebral activity based upon the frequency values.

Claim 2

A method of processing an EEG signal to provide an indication of cerebral activity in response to an event, the method comprising: sampling the EEG signal to produce digital sample values representative of amplitude of the EEG signal as a function of time; providing a plurality of digitized waveforms which are based at least in part on the digital sample values, which have a first length, and each of which includes fill values surrounding the digital sample values derived from one of a plurality of epochs having different time relationships to the event, each epoch having a second length which is less than the first length; transforming each digitized waveform from a time domain to a frequency domain to produce a frequency spectrum corresponding to one of the plurality of epochs, each frequency spectrum having frequency components uniquely attributable to the digital sample values derived from its corresponding epoch; deriving a frequency value for each epoch based upon the frequency spectrum corresponding to that epoch; and providing an output indicative of cerebral activity based upon the frequency values.

Claim 15

A method of processing a time-varying analog biological signal to provide a frequency value for each of a plurality of epochs which have different time relationships to an event, the method comprising: digitizing the biological signal to produce digital sample values representative of amplitude of the biological signal as a function of time; providing for each epoch, a first digitized waveform based at least in part upon the digital sample values derived from the epoch and in part upon fill values, the first digitized waveform having a length which is longer than the epoch; producing a frequency spectrum for each epoch based at least in part upon the first digitized waveform containing digital sample values derived from that epoch, the frequency spectrum having a frequency content which is uniquely attributable to the digital sample values derived from the epoch; and deriving a frequency value for each epoch based upon the frequency spectrum corresponding to that epoch.

Claim 16

A method of processing a time-varying analog biological signal to provide a frequency value for each of a plurality of epochs which have different time relationships to an event, the method comprising: digitizing the biological signal to produce digital sample values representative of amplitude of the biological signal as a function of time; providing for each epoch, a first digitized waveform based at least in part upon the digital sample values derived from the epoch and in part upon fill values, the first digitized waveform having a length which is longer than the epoch; producing a frequency spectrum for each epoch based at least in part upon the first digitized waveform containing digital sample values derived from that epoch, the frequency spectrum having a frequency content which is uniquely attributable to the digital sample values derived from the epoch; and deriving a frequency value for each epoch based upon the frequency spectrum corresponding to that epoch.

Claim 17

A method of processing a time-varying analog biological signal to provide an indication of biological activity in response to an event, the method comprising: digitizing the biological signal to produce digital sample values representative of amplitude of the biological signal as a function of time; providing a first non-averaged digitized waveform of a first length, the first digitized waveform including digital sample values derived from an epoch which has a time duration which is less than the first length and which has a time relationship to the event; providing a second non-averaged digitized waveform of a second length equal to the first length and partially overlapping in time with the first digitized waveform, but which does not include digital sample values derived from the epoch; transforming the first digitized waveform to a first frequency spectrum; transforming the second digitized waveform to a second frequency spectrum; producing a difference frequency spectrum representative of a difference between the first frequency spectrum and the second frequency spectrum; deriving a frequency value for the epoch based upon the difference frequency spectrum; and providing an output indicative of biological activity during the epoch based upon the frequency value for that epoch.

Claim 18

A method of processing a time-varying analog biological signal to provide an indication of biological activity in response to an event, the method comprising: digitizing the biological signal to produce digital sample values representative of amplitude of the biological signal as a function of time; providing a first non-averaged digitized waveform of a first length, the first digitized waveform including digital sample values derived from an epoch which has a time duration which is less than the first length and which has a time relationship to the event; providing a second non-averaged digitized waveform of a second length equal to the first length and partially overlapping in time with the first digitized waveform, but which does not include digital sample values derived from the epoch; transforming the first digitized waveform to a first frequency spectrum; transforming the second digitized waveform to a second frequency spectrum; producing a difference frequency spectrum representative of a difference between the first frequency spectrum and the second frequency spectrum; deriving a frequency value for the epoch based upon the difference frequency spectrum; and providing an output indicative of biological activity during the epoch based upon the frequency value for that epoch.

Claim 19

A method of processing an EEG signal, the method comprising: sampling the EEG signal during a time interval having a time relationship to an event to produce digital sample values representative of amplitude of the EEG signal as a function of time; producing, for each of a plurality of epochs having different time relationships to the event, a frequency spectrum based upon a digitized waveform which covers a time period longer than the epoch and which has a frequency content which is uniquely attributable to the digital sample values derived from that epoch; deriving, for each of the plurality of epochs, a frequency value based upon the frequency spectrum corresponding to that epoch; and providing an output as a function of the frequency values for the plurality of epochs.

Claim 20

A method of processing an EEG signal, the method comprising: sampling the EEG signal during a time interval having a time relationship to an event to produce digital sample values representative of amplitude of the EEG signal as a function of time; producing, for each of a plurality of epochs having different time relationships to the event, a frequency spectrum based upon a digitized waveform which covers a time period longer than the epoch and which has a frequency content which is uniquely attributable to the digital sample values derived from that epoch; deriving, for each of the plurality of epochs, a frequency value based upon the frequency spectrum corresponding to that epoch; and providing an output as a function of the frequency values for the plurality of epochs.

Claim 21

A method of processing an EEG signal to provide an indication of cerebral activity in response to an event, the method comprising: providing a plurality of tests which include: sampling the EEG signal to produce digital sample values representative of amplitude of the EEG signal as a function of time; providing first and second non-averaged digitized waveforms which are based at least in part upon the digital sample values and which represent first and second time intervals having essentially equal lengths but different time relationships to the event, wherein the first and second time intervals are staggered and are partially overlapping to define an epoch which has a time duration which is less than a the lengths of the first and second time intervals and which has a time relationship to the stimulus so that only one of the first and second time intervals includes digital sample values corresponding to the epoch; transforming the first and second digitized waveforms from a time domain to a frequency domain to produce a first frequency spectrum and a second frequency spectrum representative of amplitude of the EEG signal at selected frequencies during the first and second time intervals, respectively; subtracting the second frequency spectrum from the first frequency spectrum to produce a difference frequency spectrum which is a function of amplitude of the EEG signal at selected frequencies during the epoch; deriving a frequency value for the epoch based upon the difference frequency spectrum; averaging the frequency values for the epoch obtained from the plurality of tests to produce an averaged frequency value; and providing an indication of cerebral activity as a function of the averaged frequency value.

Claim 22

A method of processing an EEG signal to provide an indication of cerebral activity in response to an event, the method comprising: providing a plurality of tests which include: sampling the EEG signal to produce digital sample values representative of amplitude of the EEG signal as a function of time; providing first and second non-averaged digitized waveforms which are based at least in part upon the digital sample values and which represent first and second time intervals having essentially equal lengths but different time relationships to the event, wherein the first and second time intervals are staggered and are partially overlapping to define an epoch which has a time duration which is less than a the lengths of the first and second time intervals and which has a time relationship to the stimulus so that only one of the first and second time intervals includes digital sample values corresponding to the epoch; transforming the first and second digitized waveforms from a time domain to a frequency domain to produce a first frequency spectrum and a second frequency spectrum representative of amplitude of the EEG signal at selected frequencies during the first and second time intervals, respectively; subtracting the second frequency spectrum from the first frequency spectrum to produce a difference frequency spectrum which is a function of amplitude of the EEG signal at selected frequencies during the epoch; deriving a frequency value for the epoch based upon the difference frequency spectrum; averaging the frequency values for the epoch obtained from the plurality of tests to produce an averaged frequency value; and providing an indication of cerebral activity as a function of the averaged frequency value.

Claim 24

A system for processing an analog EEG signal, the system comprising: means for producing a first non-averaged digitized waveform representative of amplitude of the EEG signal as a function of time during a first time interval; means for producing a second non-averaged digitized waveform representative of amplitude of the EEG signal as a function of time during a second time interval, wherein the first and second intervals are essentially equal in length and staggered in time to define an overlapping portion when both intervals are occurring and a nonoverlapping portion in which only one of the intervals is occuring, the nonoverlapping portion having a time duration which is less than the length of the intervals; means for transforming the first digitized waveform to a first frequency spectrum representative of amplitude of the EEG signal as a function of frequency of the EEG signal during the first time interval; means for transforming the second digitized waveform to a second frequency spectrum representative of amplitude of the EEG signal as a function of frequency of the EEG signal during the second time interval; means for subtracting the second frequency spectrum from the first frequency spectrum to produce a difference frequency spectrum representative of amplitude of the EEG signal as a function of frequency of the EEG signal during the nonoverlapping portion; and means for providing an indication of frequency response during the nonoverlapping portion based upon the difference frequency spectrum.

Claim 25

A system for processing an analog EEG signal, the system comprising: means for producing a first non-averaged digitized waveform representative of amplitude of the EEG signal as a function of time during a first time interval; means for producing a second non-averaged digitized waveform representative of amplitude of the EEG signal as a function of time during a second time interval, wherein the first and second intervals are essentially equal in length and staggered in time to define an overlapping portion when both intervals are occurring and a nonoverlapping portion in which only one of the intervals is occuring, the nonoverlapping portion having a time duration which is less than the length of the intervals; means for transforming the first digitized waveform to a first frequency spectrum representative of amplitude of the EEG signal as a function of frequency of the EEG signal during the first time interval; means for transforming the second digitized waveform to a second frequency spectrum representative of amplitude of the EEG signal as a function of frequency of the EEG signal during the second time interval; means for subtracting the second frequency spectrum from the first frequency spectrum to produce a difference frequency spectrum representative of amplitude of the EEG signal as a function of frequency of the EEG signal during the nonoverlapping portion; and means for providing an indication of frequency response during the nonoverlapping portion based upon the difference frequency spectrum.

Claim 26

A system for processing EEG signals derived from a plurality of sites to provide an indication of cerebral activity as a function of time in response to a stimulus, the system comprising: means for providing a stimulus during each of a plurality of tests; analog-to-digital converter means for sampling each EEG signal; storage means for storing digital sample values produced by the analog-to-digital converter means for each EEG signal, the digital sample values being representative of amplitude of the corresponding EEG signal as a function of time; means for providing first and second non-averaged digitized waveforms, for each EEG signal and each test, which are based at least in part on the digital sample values and represent a first and a second time interval of essentially equal length, respectively, which define one of a plurality of epochs having different time relationships to the stimulus and a duration which is less than the lengths of the first and second time intervals, the first and second time intervals being staggered and partially overlapping and wherein the epoch is defined by presence of only one of the first and second time intervals; means for transforming the first and second digitized waveforms for each EEG signal from a time domain to a frequency domain to produce a first and a second frequency spectrum, respectively; means for subtracting the second frequency spectrum from the first frequency spectrum for each EEG signal to produce a difference frequency spectrum; means for deriving a frequency value for each EEG signal during each of the plurality of epochs based upon a corresponding difference frequency spectrum; and means for providing an indication of cerebral activity at each of a plurality of sites from which the EEG signals are derived as a function of the frequency values.

Claim 27

A system for processing EEG signals derived from a plurality of sites to provide an indication of cerebral activity as a function of time in response to a stimulus, the system comprising: means for providing a stimulus during each of a plurality of tests; analog-to-digital converter means for sampling each EEG signal; storage means for storing digital sample values produced by the analog-to-digital converter means for each EEG signal, the digital sample values being representative of amplitude of the corresponding EEG signal as a function of time; means for providing first and second non-averaged digitized waveforms, for each EEG signal and each test, which are based at least in part on the digital sample values and represent a first and a second time interval of essentially equal length, respectively, which define one of a plurality of epochs having different time relationships to the stimulus and a duration which is less than the lengths of the first and second time intervals, the first and second time intervals being staggered and partially overlapping and wherein the epoch is defined by presence of only one of the first and second time intervals; means for transforming the first and second digitized waveforms for each EEG signal from a time domain to a frequency domain to produce a first and a second frequency spectrum, respectively; means for subtracting the second frequency spectrum from the first frequency spectrum for each EEG signal to produce a difference frequency spectrum; means for deriving a frequency value for each EEG signal during each of the plurality of epochs based upon a corresponding difference frequency spectrum; and means for providing an indication of cerebral activity at each of a plurality of sites from which the EEG signals are derived as a function of the frequency values.

Claim 28

A system for processing a time-varying analog biological signal to provide a frequency value for each of a plurality of epochs which have different time relationships to an event, the system comprising: means for digitizing the biological signal to produce digital sample values representative of amplitude of the biological signal as a function of time; means for providing, for each epoch, a non-averaged digitized waveform based at least in part upon the digital sample values from the epoch, the digitized waveform having a length which is greater than a length of the epoch; means for producing a frequency spectrum for each epoch as a function of the digitized waveform for that epoch, the frequency spectrum having a frequency content which is uniquely attributable to the digital sample values from the epoch; and means for deriving the frequency value for each epoch based upon the frequency spectrum corresponding to that epoch.

Claim 29

A system for processing a time-varying analog biological signal to provide a frequency value for each of a plurality of epochs which have different time relationships to an event, the system comprising: means for digitizing the biological signal to produce digital sample values representative of amplitude of the biological signal as a function of time; means for providing, for each epoch, a non-averaged digitized waveform based at least in part upon the digital sample values from the epoch, the digitized waveform having a length which is greater than a length of the epoch; means for producing a frequency spectrum for each epoch as a function of the digitized waveform for that epoch, the frequency spectrum having a frequency content which is uniquely attributable to the digital sample values from the epoch; and means for deriving the frequency value for each epoch based upon the frequency spectrum corresponding to that epoch.

Claim 30

A system for processing an EEG signal, the method comprising: means for sampling the EEG signal during a time interval having a time relationship to an event to produce digital sample values representative of amplitude of the EEG signal as a function of time; means for producing, for each of a plurality of epochs having different time relationships to the event, a frequency spectrum based upon a digitized waveform which is longer than the epoch and which has a frequency content which is uniquely attributable to the digital sample values corresponding to that epoch; means for deriving, for each of the plurality of epochs, a frequency value based upon the frequency spectrum corresponding to that epoch; and means for providing an output as a function of the frequency values for the plurality of epochs.

Claim 31

A system for processing an EEG signal, the method comprising: means for sampling the EEG signal during a time interval having a time relationship to an event to produce digital sample values representative of amplitude of the EEG signal as a function of time; means for producing, for each of a plurality of epochs having different time relationships to the event, a frequency spectrum based upon a digitized waveform which is longer than the epoch and which has a frequency content which is uniquely attributable to the digital sample values corresponding to that epoch; means for deriving, for each of the plurality of epochs, a frequency value based upon the frequency spectrum corresponding to that epoch; and means for providing an output as a function of the frequency values for the plurality of epochs.

Claim 32

A method of processing an EEG signal to provide an indication of cerebral activity during an epoch, the method comprising: digitizing the EEG signal to produce digital sample values representative of amplitude of the EEG signal as a function of time, including at least one digital sample value representative of amplitude of the EEG signal during the epoch; forming a digitized waveform having those digital sample values which are representative of amplitude of the EEG signal during the epoch located at its center and having fill values surrounding those digital sample values; transforming the digitized waveform from a time domain to a frequency domain to produce a frequency spectrum; and deriving a frequency value for the epoch based upon the frequency spectrum.

Claim 33

A method of processing an EEG signal to provide an indication of cerebral activity during an epoch, the method comprising: digitizing the EEG signal to produce digital sample values representative of amplitude of the EEG signal as a function of time, including at least one digital sample value representative of amplitude of the EEG signal during the epoch; forming a digitized waveform having those digital sample values which are representative of amplitude of the EEG signal during the epoch located at its center and having fill values surrounding those digital sample values; transforming the digitized waveform from a time domain to a frequency domain to produce a frequency spectrum; and deriving a frequency value for the epoch based upon the frequency spectrum.