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Brain responses to olfactory and trigeminal exposure in idiopathic environmental illness (IEI) attributed to smells: An fMRI study
Umeå University, Faculty of Social Sciences, Department of Psychology.
Umeå University, Faculty of Social Sciences, Department of Psychology.
Umeå University, Faculty of Medicine, Department of Integrative Medical Biology (IMB), Physiology. Umeå University, Faculty of Medicine, Department of Radiation Sciences, Diagnostic Radiology.
Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Dermatology and Venerology.
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2014 (English)In: Journal of Psychosomatic Research, ISSN 0022-3999, E-ISSN 1879-1360, Vol. 77, no 5, 401-408 p.Article in journal (Refereed) Published
Abstract [en]

OBJECTIVE: Idiopathic environmental intolerance (IEI) to smells is a prevalent medically unexplained illness. Sufferers attribute severe symptoms to low doses of non-toxic chemicals. Despite the label, IEI is not characterized by acute chemical senses. Theoretical models suggest that sensitized responses in the limbic system of the brain constitute an important mechanism behind the symptoms. The aim was to investigate whether and how brain reactions to low-levels of olfactory and trigeminal stimuli differ in individuals with and without IEI. METHODS: Brain responses to intranasally delivered isoamyl acetate and carbon dioxide were assessed in 25 women with IEI and 26 non-ill controls using functional magnetic resonance imaging. RESULTS: The IEI group had higher blood-oxygenated-level-dependent (BOLD) signal than controls in the thalamus and a number of, mainly, parietal areas, and lower BOLD signal in the superior frontal gyrus. The IEI group did not rate the exposures as more intense than the control group did, and there were no BOLD signal differences between groups in the piriform cortex or olfactory regions of the orbitofrontal cortex. CONCLUSIONS: The IEI reactions were not characterized by hyper-responsiveness in sensory areas. The results can be interpreted as a limbic hyperreactivity and speculatively as an inability to inhibit salient extemal stimuli.

Place, publisher, year, edition, pages
Elsevier, 2014. Vol. 77, no 5, 401-408 p.
Keyword [en]
idiopathic environmental intolerance, chemical intolerance, multiple chemical sensitivity, fMRI, olfactory, trigeminal
National Category
Psychology Psychiatry
URN: urn:nbn:se:umu:diva-97003DOI: 10.1016/j.jpsychores.2014.09.014ISI: 000344718200010OAI: diva2:769486
Available from: 2014-12-08 Created: 2014-12-08 Last updated: 2015-12-16Bibliographically approved

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Andersson, LinusClaesson, Anna-SaraNyberg, LarsStenberg, BerndtNordin, Steven
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