Neural mechanisms underlying anxiety-related deficits of attentional inhibition: direct ERP evidence from the Pd component

Behavioral evidence shows that anxious individuals tend to be distracted by irrelevant stimulation not only for threat-related stimuli but also for non-emotional neutral stimuli. These findings suggest that anxious individuals may have a general impairment of attentional control, especially inhibition function. However, the neural mechanism underlying the anxiety-related impairment in attentional control is unclear. Here, in a visual search task with geometric stimuli, we examined attentional processing of the non-emotional neutral distractor on participants with different levels of anxiety, using the event-related-potential (ERP) indices of attentional selection (N2 posterior contralateral [N2pc]) and top-down inhibition (distractor positivity [Pd]). We found that distractor-evoked Pd amplitudes were negatively correlated with trait-anxiety scores, i.e., the higher the level of anxiety, the worse the ability of attentional inhibition. In contrast, the amplitudes of distractor-evoked N2pc did not vary with anxiety levels, suggesting that trait-anxiety level does not affect stimulus-driven attentional capture. We also observed attentional processing of target stimuli and found that the peak latency of target-evoked N2pc was delayed as anxiety levels rise, suggesting that anxiety impairs the efficiency of top-down attentional selection of the target. The present study provides direct neurophysiological evidence for general anxiety-related impairment of attentional control.