Single trial detection in encephalography

Abstract

An EEG cap ( 8 ) having 64 or 128 electrodes ( 10 ) is placed on the head of the subject ( 11 ) who is viewing CRT monitor ( 14 ). The signals on each channel are amplified by amplifier ( 17 ) and sent to an analog-to-digital converter ( 20 ). PC ( 23 ) captures and records the amplified signals and the signals are processed by signal processing PC ( 26 ) performing linear signal processing. The resulting signal is sent back to a feedback/display PC ( 29 ) having monitor ( 14 ). An EEG cap ( 8 ) having 64 or 128 electrodes ( 10 ) is placed on the head of the subject ( 11 ) who is viewing CRT monitor ( 14 ). The signals on each channel are amplified by amplifier ( 17 ) and sent to an analog-to-digital converter ( 20 ). PC ( 23 ) captures and records the amplified signals and the signals are processed by signal processing PC ( 26 ) performing linear signal processing. The resulting signal is sent back to a feedback/display PC ( 29 ) having monitor ( 14 ).

We claim: 
     
         1 . A method for interpreting sampled brain activity signals of a subject subjected to at least a first stimulus and a second stimulus, comprising:
 (a) identifying, using a processing arrangement, one or more sets of samples from the sampled brain activity signals corresponding to a first response to the first stimulus;   (b) identifying one or more sets of samples corresponding to a second response to the second stimulus; and   (c) determining two or more spatial weighting coefficients such that a linear response maximally discriminates between the one or more sets of samples corresponding to the first response and the one or more sets of samples corresponding to the second response.   
     
     
         2 . The method of  claim 1 , wherein the sampled brain activity signals comprise two or more sensor signals generated by two or more corresponding members of an array of brain activity sensors in proximity to a head of the subject. 
     
     
         3 . The method of  claim 2 , further comprising amplifying each of the two or more sensor signals. 
     
     
         4 . The method of  claim 3 , further comprising converting each of the two or more sensor signals using an analog-to-digital converter. 
     
     
         5 . The method of  claim 2 , wherein determining two or more spatial coefficients comprises applying a linear classifier to each of the two or more sensor signals. 
     
     
         6 . The method of  claim 1 , wherein the first response comprises a motor response of the subject. 
     
     
         7 . The method of  claim 1 , wherein the first response comprises a right button push and a second response comprises a left button push. 
     
     
         8 . The method of  claim 1 , wherein the one or more samples corresponding to the first response comprise:
 a first sample corresponding to a first instance of the first response; and   a second sample corresponding to a second instance of the first response.   
     
     
         9 . The method of  claim 1 , wherein the one or more samples corresponding to the first response comprise, for each sample, a predetermined number of samples prior to the first response. 
     
     
         10 . The method of  claim 1 , wherein the one or more samples corresponding to the first response comprise, for each sample, a predetermined number of samples following the first stimulus. 
     
     
         11 . The method of  claim 1 , wherein determining two or more spatial weighting coefficients comprises using a linear discrimination method. 
     
     
         12 . The method of  claim 1 , further comprising:
 obtaining a set of samples following a stimuli;   weighting the set of samples using the two or more spatial weighting coefficients; and   generating an output signal based on the weighted set of samples having a high correlation to one of the one or more sets of samples corresponding to the first response and the one or more sets of samples corresponding to the second response.   
     
     
         13 . The method of  claim 12 , wherein generating an output signal comprises linearly integrating the weighted set of samples. 
     
     
         14 . A system for interpreting sampled brain activity signals of a subject subjected to at least a first stimulus and a second stimulus, comprising:
 an input adapted to receive sampled brain activity signals; and   a data processor, coupled to the input, programmed to:
 receive the sampled brain activity signals from the input; 
 identify one or more sets of samples from the sampled brain activity signals corresponding to a first response to the first stimulus; 
 identify one or more sets of samples corresponding to a second response to the second stimulus; and 
 determine two or more spatial weighting coefficients such that a linear response maximally discriminates between the one or more sets of samples corresponding to the first response and the one or more sets of samples corresponding to the second response. 
   
     
     
         15 . The system of  claim 14 , further comprising an array of brain activity sensors coupled to the input. 
     
     
         16 . The system of  claim 15 , wherein the array of brain activity sensors are positioned on a cap. 
     
     
         17 . The system of  claim 16 , wherein the cap comprises an EEG cap. 
     
     
         18 . The system of  claim 15 , wherein the array of brain sensors comprises a plurality of silver chloride electrodes. 
     
     
         19 . The system of  claim 14 , further comprising an amplifier coupled to the input. 
     
     
         20 . The system of  claim 14 , further comprising an analog-to-digital converter coupled to the input.