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Paper Review:
Noureddin et. al.
Online Removal of Eye Movement and Blink EEGArtifacts Using a High-Speed Eye Tracker
Presented ByMd Kafiul Islam
A0080155M
Outline• Introduction
Motivation
• Paper Summery Main Contribution: Eye Tracker based OA Removal
Performance Evaluation
Results
• Conclusion• Q & A
Motivation OA Removal from EEG
• High Speed Eye tracker• Both Eye Blink and Eye Movement• No Requirement of EOG electrodes• Online Removal for S-EEG based BI
Limitations of EOG Electrodes – Also contain brain waves– Not suitable for practical daily applications
Eye TrackerEOG Lead Locations
Simultaneous EEG + EOG
Eye Blink Artifacts
Eye Movement Artifacts
Eye Tracking and OA Removal
General approach to OA removal
Overall operation of eye tracker for every image captured.
Areas of eye tracker images used for extracting blink signal
Example of Eye Tracking
Eye tracking versus EOG during (a) simultaneous horizontal (left) and vertical (up) saccade, and (b) blink. Sample eye images are shown above and EOG and eye tracking signals below, with arrows pointing to the time instant each
image was captured. In (a), the x shows the current pupil position, and the dot shows the pupil position at the start of the saccade. In (b), the ellipse shows the area where the intensity value is tracked during the blink.
Performance EvaluationTwo Algorithms for Adaptive Filter:
1) RLS (fast convergence)2) H ∞ (better accuracy)
Reference Inputs (X)1) EOG2) f-EEG3) ET + f-EEG
Z -> BPF (0.5-30 Hz) -> BET
‘R’ Metric for Evaluation
Results (Cont…)
Logarithm of mean R values for (a) RLS and (b) H∞ algorithms during small upward saccades. Electrodes where the difference between means is significant are highlighted with boxes. Amplitudes are scaled the same in both (a) and (b)
to show the relative performance of the algorithms at each electrode.
RLS H∞
Conclusion
First use of a high-speed eye tracker for online OA removal (blink +
movement)
Eliminating EOG electrodes attached to the face is important for practical
daily applications (Combined EEG + Eye tracking for other applications, e.g. saccade-
and fixation-related potentials, fixation control, HCI, fatigue/saliency detection, etc.)
A new algorithm (BSG) for extracting a blink’s time course from eye
tracker images (Calibration-free method)
The performance is tested on real EEG for both RLS and H∞ algorithms
using 1) EOG; 2) f-EEG; and 3) ET with f-EEG and resulted better than conventional
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