How Task Load Modulates the Effect of State Anxiety on Working Memory and Its Neural Mechanisms: Evidence from Verbal...

The impact of state anxiety on working memory (WM) and its neural mechanisms, especially the role of task load, remain uncertain. To address this issue, we conducted two experiments to examine how state anxiety affects WM under different task loads and whether these effects are consistent across verbal and spatial modalities. State anxiety was elicited using the threat-of-shock paradigm, while participants alternately completed n-back tasks (1-back and 3-back) under safe and threat conditions, with brain activity monitored via functional near-infrared spectroscopy (fNIRS). In Experiment 1 (verbal n-back), anxiety did not affect 1-back accuracy but improved 3-back accuracy. Neurally, anxiety reduced activation in the right posterior parietal cortex (PPC) and left premotor cortex (PMC) during the 1-back task. In contrast, during the 3-back task, anxiety enhanced activation in the bilateral ventrolateral prefrontal cortex, medial prefrontal cortex, and right PPC, and increased the brain network's small-world property and normalized clustering coefficient. In Experiment 2 (spatial n-back), anxiety impaired 1-back accuracy but enhanced 3-back accuracy. Neurally, anxiety reduced left dorsolateral prefrontal cortex (dlPFC)-PMC connectivity during the 1-back, but enhanced this connectivity and bilateral dlPFC-left PPC connectivity during the 3-back, along with increased global efficiency and decreased normalized characteristic path length of brain networks. In summary, anxiety effects varied with task load, with different patterns observed in verbal and spatial WM, and their neural mechanisms involve changes in executive control network activity. These findings are interpreted through the Top-Down Emotion Control Perspective and the Two-Component Model of Anxiety.