Fixation-locked measurement of brain responses to stimuli

A method of single-trial detection of significant cognitive responses to stimuli, comprising:

• measuring EEG data of an operator's brain activity to stimuli from a plurality of electrodes placed on the operator's scalp;
• tracking the operator's free eye movement to determine fixation events;
• applying a fixation-locked window to the EEG data to generate a time segment of EEG data for each said fixation event, wherein the fixation-locked window comprises a pre-fixation window including EEG data before the fixation event and a post-fixation window including EEG data after the fixation event;
• extracting one or more features from each time segment of EEG data;
• for each said fixation event, presenting said one or more features to a classifier to generate a fixation-locked cue indicative of whether the operator exhibited a significant cognitive response to a presented stimulus;
• and
• outputting a sequence of the cues with a time code of the associated fixation event.

A method of single-trial detection of significant cognitive responses to stimuli, comprising:

• measuring EEG data of an operator's brain activity to stimuli from a plurality of electrodes placed on the operator's scalp;
• providing a time-code for the stimuli;
• tracking the operator's free eye movement to determine fixation events;
• applying a fixation-locked window to the EEG data to generate a time segment of EEG data for each said fixation event;
• extracting one or more features from each time segment of EEG data;
• for each said fixation event, presenting said one or more features to a classifier to generate a fixation-locked cue indicative of whether the operator exhibited a significant cognitive response to a presented stimulus;
• outputting a sequence of the cues with a time code of the associated fixation event;
• and
• correlating the time-code of the output cues with the time code of the stimuli.

An apparatus for single-trial detection of significant cognitive responses to stimuli, comprising:

• a plurality of electrodes configured to be placed on the operator's scalp that measure EEG data of the operator's brain activity to stimuli;
• an eye-tracking device that tracks the operator's free eye movement and generates eye movement signals;
• a fixation processor that processes the eye movement signals to generate time-code fixation events;
• a signal processor that applies a pre-fixation window to generate a time segment of EEG data before the fixation event and a post-fixation window to generate a time segment of EEG data after the fixation event to the EEG data for each said fixation event;
• and
• a cognitive response processor comprising a feature extractor that extracts one or more features from the EEG data in each of the pre-fixation and post-fixation windows for each time segment of EEG data and presents said one or more features to pre-fixation and post-fixation locked classifiers, respectively, to generate pre-fixation and post-fixation cues that are presented to a fusion classifier to generate a sequence of fixation-locked time-coded cues indicative of whether the operator exhibited a significant cognitive response to a stimulus.

An apparatus for single-trial detection of significant cognitive responses to stimuli, comprising:

• a plurality of electrodes configured to be placed placed on the operator's scalp that measure EEG data of the operator's brain activity to stimuli;
• an eye-tracking device that tracks the operator's free eye movement and generates eye movement signals;
• a fixation processor that processes the eye movement signals to generate time-code fixation events;
• a signal processor that applies a fixation-locked window to the EEG data to generate a time segment of EEG data for each said fixation event, wherein said signal processor subdivides the time segment EEG data into a plurality of time sub-segments each with a different offset to the fixation-event;
• and
• a cognitive response processor comprising a feature extractor that extracts one or more features from each said time sub-segment of EEG data and presents the extracted features to a respective plurality of spatial sub-classifiers trained to detect spatial patterns of said extracted features during different time sub-segments and to generate first level outputs indicative of the occurrence or absence of a significant brain response, said plurality of first level outputs presented to a temporal classifier trained to detect temporal patterns across the different time sub-segments relating to the evolution of the non-stationary brain response to task-relevant stimulus and to generate a second level output as a sequence of fixation-locked time-coded cues indicative of the occurrence or absence of the significant non-stationary brain response to a stimulus.

A method of training a classifier for single-trial detection of significant cognitive responses to pre-fixation and post-fixation stimuli, comprising:

• monitoring a subject's EEG signals and eye-movement;
• displaying a pattern of targets and non-targets to the subject;
• highlighting in sequence a different one of the targets or non-targets causing the subject's eyes to saccade to the highlighted target or non-target;
• monitoring subject input indicating subject detection of a highlighted target;
• processing the subject's eye-movement to determine a fixation-event for each highlighted target or non-target;
• applying a fixation-locked window to the EEG data to generate a time segment of EEG data for each fixation-event;
• extracting one or more features from said time segment of EEG data;
• and
• for each said fixation event, presenting said one or more features and a target/non-target supervised output to train the classifier to generate a fixation-locked cue indicative of whether the subject exhibited a significant cognitive response to a target.