Effects of task load, spatial attention, and trait anxiety on neuronal responses to fearful and neutral faces

There is an ongoing debate on how different components of the event-related potential (ERP) to threat-related facial expressions are modulated by attentional conditions and interindividual differences in trait anxiety. In the current study (N = 80), we examined ERPs to centrally presented, task-irrelevant fearful and neutral faces, while participants had to solve a face-unrelated visual task, which differed in difficulty and spatial position. Critically, we used a fixation-controlled experimental design and ensured the spatial attention manipulation by spectral analysis of the EEG. Besides the factors emotion, spatial attention, and perceptual load, we also investigated correlations between trait anxiety and ERPs. While P1 emotion effects were insignificant, the N170 was increased to fearful faces regardless of load and spatial attention conditions. During the EPN time window, a significantly increased negativity for fearful faces was observed only during low load and spatial attention to the face. We found no significant relationship between ERPs and trait anxiety, questioning the hypothesis of a general hypersensitivity toward fearful expressions in anxious individuals. These results show a high resistance of the N170 amplitude increase for fearful faces to spatial attention and task load manipulations. By contrast, the EPN modulation by fearful faces index a resource-dependent stage of the ERP, requiring both spatial attention at the location of faces and low load of the face-irrelevant task.