Objective. This study presents a novel methodological approach for
incorporating information related to the peripheral sympathetic response into the
investigation of neural dynamics. Particularly, we explore how hedonic contextual
olfactory stimuli influence the processing of neutral faces in terms of sympathetic
response, event-related potentials (ERPs) and effective connectivity analysis.
The objective is to investigate how the emotional valence of odors influences
the cortical connectivity underlying face processing and the role of face-induced
sympathetic arousal in this visual-olfactory multimodal integration. Approach. To
this aim, we combine electrodermal activity (EDA) analysis and dynamic causal
modeling (DCM) to examine changes in cortico-cortical interactions. Results. The
results reveal that stimuli arising sympathetic EDA responses are associated with
a more negative N170 amplitude, which may be a marker of heightened arousal
in response to faces. Hedonic odors, on the other hand, lead to a more negative
N1 component and a reduced the vertex positive potential (VPP) when they are
unpleasant or pleasant. Concerning connectivity, unpleasant odors strengthen
the forward connection from the inferior temporal gyrus (ITG) to the middle
temporal gyrus (MTG), which is involved in processing changeable facial features.
Conversely, the occurrence of sympathetic responses after a stimulus is correlated
with an inhibition of this same connection and an enhancement of the backward
connection from ITG to the fusiform face gyrus. Significance. These findings
suggest that unpleasant odors may enhance the interpretation of emotional
expressions and mental states, while faces capable of eliciting sympathetic arousal
prioritize identity processing.