Beta and Theta Oscillations Differentially Support Free Versus Forced Control over Multiple-Target Search

Area of Science:

• Cognitive Neuroscience
• Visual Perception
• Human Factors

Background:

• Multiple-target visual search is crucial in various settings but poorly understood.
• Existing research lacks clarity on how attention is controlled when searching for more than one item.

Purpose of the Study:

• To investigate the behavioral and neural mechanisms of multiple-target visual search.
• To test the theory that search efficiency depends on the mode of cognitive control.
• To differentiate between proactive and reactive control mechanisms in visual search.

Main Methods:

• Combined electroencephalography (EEG) and eye tracking.
• Participants searched for two targets in either a proactive (both targets present, free prioritization) or reactive (only one target present, imposed prioritization) control context.
• Analyzed EEG power spectral densities in beta (15-35 Hz) and delta/theta (2-8 Hz) bands.

Main Results:

• Proactive control showed pre-stimulus beta-band power suppression predicting target selection switches.
• Reactive control showed post-stimulus delta/theta band power enhancement predicting oculomotor switch costs.
• Distinct neural signatures were identified for proactive and reactive cognitive control during multiple-target search.

Conclusions:

• Multiple target representations are differentially prioritized during visual search.
• Distinct neural mechanisms underlie proactive and reactive control of multiple-target search.
• Findings provide the first clear evidence for two control modes in multiple-target search with unique EEG signatures.