Task-irrelevant filler items alter the dynamics of electrical brain activity during visual search

Area of Science:

• Cognitive Neuroscience
• Visual Perception
• Electrophysiology

Background:

• Task-irrelevant fillers are commonly used in electroencephalography (EEG) visual search studies.
• Fillers are generally assumed to be inconsequential for performance and neural activity.

Purpose of the Study:

• To investigate the impact of fillers on target and distractor processing during visual search.
• To examine how fillers influence lateralised event-related potentials (ERPs), specifically the N2pc and Ptc components.

Main Methods:

• Participants performed a visual search task with two task-relevant items (TRIs), presented with or without fillers.
• Lateralised event-related potentials (ERPs), including the N2pc and Ptc, were recorded and analyzed.
• Performance metrics were collected to assess the effect of fillers on search efficiency.

Main Results:

• Fillers enhanced and delayed attentional deployment, as indicated by N2pc modulation.
• Distractor processing, reflected by Ptc, was delayed by the presence of fillers.
• ERP modulation by fillers varied based on the distance between TRIs and the colour contrast.

Conclusions:

• Task-irrelevant fillers significantly affect lateralised electrophysiological activity during visual search.
• Fillers are not inconsequential and influence both attention allocation and distractor processing.
• The findings challenge the traditional view of fillers in EEG visual search paradigms.