Since 2014, when the first version of Add Channels was released, we have been supporting and providing high-quality software solutions for the EEG – Eye Tracking research community. The interest in eye tracking, the development of robust stationary and mobile eye tracking technologies and the positive impact of its many applications has continued to keep growing continously since then. Following this trend, an increasing demand for expanding the support for other data formats has been acknowledged. Therefore, we now support Tobii Pro Lab data and upgraded our Add Channels transform in BrainVision Analyzer accordingly.
In our collaboration with Tobii Pro AB, we have reached important milestones in the best interest of our customers:
1. Tobii Pro AB released a new eye tracking format, the Tobii Pro Lab Output Format (PLOF, v.2). This text-based format is version-numbered and rich in meta-data. It can accommodate agile changes and new features while maintaining backward compatibility with the new Add Channels implementation. For more about the data format, see Tobii Pro Lab User Manual.
2. We have released a new Add Channels pipeline for importing PLOF data with an improved user interface. Among other features, it is faster, easier to use, able to import multiple files in one go, equipped with better algorithms for synchronization and interpolation. The offline synchronization relies on common markers sent to EEG and eye tracking devices at the same time.
All formats supported by the Add Channels transform are listed below:
Note that within the PLOF file it is also possible to import data streams from other devices besides eye tracker (i.e. GSR, Accelerometer, Gyroscope, Mouse).
The new user interface provides statistical measures and a histogram of the residual synchronization error. This makes it possible to adjust parameters at an early stage without running the full integration of data and events.
The figure below illustrates an example of EEG and eye tracking (PLOF) data integration using the Add Channels transform in Analyzer 2.2.1.
Figure 1: Illustration of synchronization accuracy via the histogram and statistical measures of the synchronization error (left). Perfect alignment of EOG and Gaze channels (middle) with zero time-lag quantified by the cross-correlation plot (right).
The distribution of the residual synchronization errors (Figure 1, left) demonstrates a good level of synchronization. The histogram of sync errors shows most of the test markers are centered around zero (i.e., with a latency difference of 0.4 ms). One single blink event in the EOG channel is perfectly aligned with the same event as captured by the Tobii Pro eye tracker in the “Gaze point Y” channel (Figure 1, middle). Finally, the application of the Cross-Correlation transform provides further quantitative evidences of very good integration. The cross-correlation Cross(EOG,Gaze point Y) shows a peak centered at 0, with no time lag in the millisecond scale (Figure 1, right).