Non-Target Suppression Supports the Formation of Representational Prioritization Under High Working Memory Load.

Target enhancement and non-target suppression are two critical mechanisms underlying representational prioritization in visual working memory (VWM). However, it remains unclear how VWM load modulates these prioritization mechanisms. Using EEG combined with a retro-cue paradigm, this study investigated how representational prioritization emerges under low (Experiment 1) and high (Experiment 2) memory load conditions. Behavioral results showed that under low load, both target and non-target items benefited from retro-cue. ERP analyses revealed significantly larger P2 and P3b amplitudes in response to valid compared to neutral retro-cues, whereas no significant contralateral delay activity (CDA) component was observed. Under high load, cueing benefits were restricted to target items, whereas non-target items suffered impaired performance. ERP analyses again showed enhanced P2 and P3b amplitudes for valid compared to neutral retro-cues, but a significant CDA component was also observed. Time-frequency analyses further revealed frontal theta synchronization (ERS) and posterior alpha desynchronization (ERD) under both load conditions. Notably, theta-alpha phase-amplitude coupling (PAC) was significantly stronger for valid than neutral retro-cues under low load, whereas under high load, PAC did not significantly differ between cue conditions. Together, these findings suggest that target enhancement serves as a stable mechanism for representational prioritization, whereas non-target suppression critically depends on resource availability. VWM load systematically shapes representational prioritization through modulation of oscillatory timing characteristics and inter-regional neural coordination.