EEG Signal Dynamics in Unrestricted Natural Visual Search

EEG signal dynamics in unrestricted natural visual search: By Alexander Varatharajah. Visual search is a skill that if not mastered, would leave you considerably unfit for Darwin’s idea of survival. Prior knowledge of the cognitive processes involved in visual search stemmed from modelling and behavioural studies collecting subjects’ reaction times, their eye movements, or EEG target signatures under fixed-gaze. To further understand these concepts, progression has to be made with the collection of data. Recent co-registration of EEG and Eye-Tracking has further enhanced this understanding by allowing brain responses to be seen in the form of fixation-Related Potentials (fRPs). To date, only a handful of studies have investigated brain correlates of visual search paradigms involving eye-movements. In this research, subjects search for targets in natural images, resembling the children’s game; “Where’s Waldo?” Results show early and late target detection effects. Also presented is a novel full trial analysis, that has allowed investigation into local and global fRPs driving characteristics, which were related to classical concepts of expectancy and surprise. Additionally, potential pitfalls from commonly used techniques are highlighted.