Washington: Researchers have used powerful new brain imaging technologies to reveal how anxiety or stress can rewire the brain, linking centers of emotion and olfactory processing, to make typically benign smells malodorous.
A team led by Wen Li, a professor of psychology at the University of Wisconsin-Madison Waisman Center, reports that the brains of human subjects experience anxiety induced by disturbing pictures and text of things like car crashes and war transform neutral odors to distasteful ones, fueling a feedback loop that could heighten distress and lead to clinical issues like anxiety and depression.
Li conducted the study with UW-Madison colleagues Elizabeth Krusemark and Lucas Novak, and Darren Gitelman of Northwestern University's Feinberg School of Medicine.
Li said that people experiencing an increase in anxiety show a decrease in the perceived pleasantness of odors. It becomes more negative as anxiety increases.
Using behavioral techniques and functional magnetic resonance imaging (fMRI), Li's group looked at the brains of a dozen human subjects with induced anxiety as they processed known neutral odors.
In the course of the experiment, the team observed that two distinct and typically independent circuits of the brain - one dedicated to olfactory processing, the other to emotion - become intimately intertwined under conditions of anxiety.
Subsequent to anxiety induction and the imaging process, subjects were asked again to rate the panel of neutral smells, most assigning negative responses to smells they previously rated as neutral.
Li said that in typical odor processing, it is usually just the olfactory system that gets activated but when a person becomes anxious, the emotional system becomes part of the olfactory processing stream.
The study has been published in the Journal of Neuroscience.