Acute stress alters affective habituation and olfactory-limbic activity during repeated odor exposure in men

Sensory affective habituation reflects the dynamic adjustment of affective responses during repeated sensory exposure and is an important component of adaptive affective processing. Acute psychological stress may alter this process, yet its neural mechanisms remain poorly understood. The present study examined how acute stress modulates affective and neural responses during repeated exposure to two odor stimuli differing in affective valence. Twenty-four healthy young men completed the Socially Evaluated Cold Pressor Test (SECPT) and a non-stressful control condition in separate sessions, followed by an olfactory habituation functional magnetic resonance imaging (fMRI) paradigm with repeated online ratings of odor pleasantness and intensity. Behaviorally, acute stress accelerated affective habituation across repeated exposure to the two odor stimuli, with no reliable evidence that this effect differed between PEA and FMA. ROI-based fMRI analyses showed reduced overall responses under stress in the hippocampus, piriform cortex, and orbitofrontal cortex. Exploratory ROI analyses revealed that the hippocampus showed nominal stress-related alterations in response dynamics across repeated odor exposure, with no reliable evidence that this effect differed between the two odor stimuli; however, this effect did not survive correction across the predefined ROIs and requires independent replication. Together, these findings indicate that acute stress alters subjective affective habituation during repeated olfactory stimulation and modulates overall responses within olfactory-limbic regions, while providing preliminary evidence for altered hippocampal response dynamics.