Distinguishing between target and nontarget fixations in a visual search task using fixation-related potentials

Area of Science:

• Cognitive Neuroscience
• Neuroscience
• Human-Computer Interaction

Background:

• The P300 event-related potential (ERP) is a known neural marker for target detection.
• Current P300 applications typically require participants to maintain eye fixation during stimulus presentation.
• Investigating alternative EEG-based methods for analyzing visual attention during naturalistic eye movements is crucial.

Purpose of the Study:

• To explore the use of fixation-related potentials (FRPs) for differentiating target from nontarget fixations during a visual search task.
• To determine if single FRPs, synchronized to fixation onset, can be classified above chance.
• To establish a foundation for real-time monitoring of observer interest and support for search tasks.

Main Methods:

• Participants performed a visual search task involving Landolt Cs, systematically scanning displays.
• Electroencephalography (EEG) epochs were synchronized to fixation onset, creating fixation-related potentials (FRPs).
• FRPs were analyzed to distinguish between fixations on target stimuli and nontarget stimuli.

Main Results:

• A P300-consistent FRP component was identified, reliably differentiating target from nontarget fixations.
• Single FRPs were classified as target or nontarget with an average accuracy of 62%, significantly above the 50% chance level.
• These findings demonstrate the feasibility of using FRPs to decode visual attention during eye movements.

Conclusions:

• Fixation-related potentials (FRPs) offer a viable method for inferring visual attention during naturalistic eye movements.
• This technique advances beyond traditional P300 paradigms by not requiring sustained fixation.
• The results pave the way for applications in covert attention monitoring and eye-movement-based assistance in search tasks.