by Dr. Roland Csuhaj
Scientific Consultant (Brain Products)
The EyeLink 1000 Plus Eye Tracker of SR Research joins the ASL, SMI and Tobii devices: from now on it too is supported by the Add Channels transformation of BrainVision Analyzer 2. How can an eye tracker help your EEG research?
The Add Channels transformation of Analyzer was introduced last year. It has the remarkable capability to expand the data acquisition beyond EEG and sensors, since it imports and synchronizes co-registered data streams to EEG. The tool supported three types of eye tracker (ASL, SMI and Tobii) and we promised more devices would be added.
Brain Products now proudly announces the support of SR Research EyeLink 1000 Plus Eye Tracker data. The EyeLink 1000 Plus has some remarkable features, for example it offers ultrahigh sampling rates and recording in an MR environment. As explained in the introduction article to the Add Channels transformation, the synchronization between EEG and eye tracker data is based on common markers. It is easy to share triggers between Brain Products’ systems and the EyeLink 1000 Plus, since both handle the same type of hardware (TTL) markers. The eye tracker data is imported together with eye events like fixation, blinks, entering or leaving area of interest, and saccades. Such events appear as markers in the joint file.
The eye events are helpful in many ways during the data evaluation. Obviously they make it possible to analyze the effect on the EEG. A good example is the microsaccade, which induces gamma-band response. Similar oscillations could be generated by neurons as well, and the eye tracker helps to differentiate between the two types of signal. It is always good to know where the subject was looking. Using only trials in which the desired stimulus was the focus of attention improves the signal to noise ratio, especially if the subject is not cooperative and many trials have to be rejected. The logic could be inverted and the position of the gaze could be the basis of segment categorization, which opens new possibilities in experimental planning. Talking about experiment design, most control software is able to get the eye position online and modify the stimulus presentation accordingly. Starting the experiment only when the subject reads the instruction is just the tip of the iceberg. For more information about the possible software hardware combinations, please visit the manufacturers’ websites.
An eye tracker device is a valuable add on for practically all visual EEG experiments and the Add Channels transformation of Analyzer makes it quick and easy to merge the co-registered data files. Are you interested in the Add Channel add-on license? Contact firstname.lastname@example.org.
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