Introduction: Emotional stimulus is processed automatically in a bottom-up way or can be
processed voluntarily in a top-down way. Imaging studies have indicated that bottom-up and
top-down processing are mediated through different neural systems. However, temporal
differentiation of top-down versus bottom-up processing of facial emotional expressions has
remained to be clarifed. The present study aimed to explore the time course of these processes
as indexed by the emotion-specifc P100 and late positive potential (LPP) event-related potential
(ERP) components in a group of healthy women.
Methods: Fourteen female students of Alzahra University, Tehran, Iran aged 18–30 years,
voluntarily participated in the study. The subjects completed 2 overt and covert emotional tasks
during ERP acquisition.
Results: The results indicated that fearful expressions signifcantly produced greater P100
amplitude compared to other expressions. Moreover, the P100 fndings showed an interaction
between emotion and processing conditions. Further analysis indicated that within the overt
condition, fearful expressions elicited more P100 amplitude compared to other emotional
expressions. Also, overt conditions created signifcantly more LPP latencies and amplitudes
compared to covert conditions.
Conclusion: Based on the results, early perceptual processing of fearful face expressions is
enhanced in top-down way compared to bottom-up way. It also suggests that P100 may re?ect an
attentional bias toward fearful emotions. However, no such differentiation was observed within
later processing stages of face expressions, as indexed by the ERP LPP component, in a topdown versus bottom-up way. Overall, this study provides a basis for further exploring of bottomup and top-down processes underlying emotion and may be typically helpful for investigating the
temporal characteristics associated with impaired emotional processing in psychiatric disorders.