Fixation-related potentials in visual search: A combined EEG and eye tracking study

Abstract

We report a study of concurrent eye movements and electroencephalographic (EEG) recordings while subjects freely explored a search array looking for hidden targets. We describe a sequence of fixation-event related potentials (fERPs) that unfolds during ∼ 400 ms following each fixation. This sequence highly resembles the event-related responses in a replay experiment, in which subjects kept fixation while a sequence of images occurred around the fovea simulating the spatial and temporal patterns during the free viewing experiment. Similar responses were also observed in a second control experiment where the appearance of stimuli was controlled by the experimenters and presented at the center of the screen. We also observed a relatively early component (∼150 ms) that distinguished between targets and distractors only in the freeviewing condition. We present a novel approach to match the critical properties of two conditions (targets/distractors), which can be readily adapted to other paradigms to investigate EEG components during free eye-movements.

EEG correlates of active visual search during simulated driving: An exploratory study

“…Despite the existence of a large amount of studies describing EFRPs, almost all of them are performed in well-controlled laboratory studies using simple stimuli [11]. More important, even those studies using more natural stimuli typically employ static images, avoid gaze shifts or instructed subjects to fixate during long periods (>300ms) [8], [12], [13]. This has allowed to identify discriminat late EFRP components [8], even at a single subject level [11].…”

“…The symbols were chosen because they are geometrically and saliently equivalent. The surrounding # signs are there to create a crowding effect and force the foveating in the center of the board [8]. The boards are evenly spaced by 30 m, and placed randomly on either side of the street.…”

“…Previous work has reported such correlates in visual search tasks for static and simple images with and without eye movements [6]- [8], [9]. They suggest that evoked EEG responses can be decoded to identify when a subject perceives a target image amid a sequence of other stimuli.…”

“…In these experiments, using the so called rapid serial visual protocol, the subject fixates on a screen while he/she observes images presenting at the same location [6], [7]. More recently, this type of analysis has been extended to cases where subjects are allowed to freely move their eyes to scan larger, more complex images [8], [9].…”

Quality control of geological voxel models using experts' gaze

“…Another route of improving the model would be to add information from brain signals. It has been shown that by relating EEG traces to eye fixations, it is possible to distinguish above chance whether an observer is looking at a looked-for target (which in this case would be a geological model error) or not (Brouwer et al, 2013(Brouwer et al, , 2014Kamienkowski et al, 2012).…”