Bachelor Thesis BCLR-2022-109

BibliographyLokman, Fadil Furkan: Data Analysis of Combined EEG/EyeTracking Timeseries: Orientation-effects.
University of Stuttgart, Faculty of Computer Science, Electrical Engineering, and Information Technology, Bachelor Thesis No. 109 (2022).
43 pages, english.

Context. There is an increasingly high demand for eye tracking experiments under free viewing conditions in which neural activity gets measured. Problem. To analyze certain effects in measured brain responses in an isolated manner, one has to discard all other effects that overlap with the effect of interest. However, our knowledge about the implications of eye movement on the measured Electroencephalography (EEG) signals is very limited and due to eye movements occurring very frequently during free viewing paradigms, their related EEG responses cause many overlaps. Objective. Dimigen and Ehinger recently researched the effect of the absolute angle of a saccade on the measured EEG signals [DE21]. I intended to replicate their experiment with new datasets to determine if their results are consistent. Furthermore, to add additional insights into the not yet well-researched field of eye motion effects on EEG data, I also analyzed whether the relative angle between two subsequent saccades has a significant effect on the EEG data after fixation onset. Method. To correct for overlaps in the measured EEG signals, I used deconvolution offered by the Unfold Toolbox by Ehinger and Dimigen [ED19], and to model the effects in the data, I used a function for regression with circular splines that I implemented myself. Moreover, I used two datasets in my research to cross-validate my results. Result. In my analysis of the absolute angle effects, I found the same results reported by Dimigen and Ehinger [DE21]. Saccades to the right cause high fixation-related potentials (FRPs) in the brain’s left hemisphere, and saccades to the left cause high FRPs in the brain’s right hemisphere. Furthermore, for the relative angle, I found a rather small negative effect in occipital electrodes for saccades with a relative angle of +-180, 200-300ms after fixation onset. Conclusion. The results of my thesis reflect and reevaluate previous findings regarding fixation effects on the EEG and open room for new discussions about the impact of the relative angle between two saccades on the FRPs.

Department(s)University of Stuttgart, Institute of Visualisation and Interactive Systems, Visualisation and Interactive Systems
Superviser(s)Ehinger, Jun.-Prof. Benedikt; Schepers, Judith
Entry dateNovember 14, 2023
   Publ. Computer Science