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Proc Natl Acad Sci U S A. 2017 Jun 13;114(24):6400-6405. doi: 10.1073/pnas.1617357114. Epub 2017 May 22.

Behavioral and neural correlates to multisensory detection of sick humans.

Author information

Division of Psychology, Department of Clinical Neuroscience, Karolinska Institutet, 171 77 Stockholm, Sweden;
Department of Psychiatry, Psychotherapy and Psychosomatics, Medical School, Rheinisch-Westfälische Technische Hochschule Aachen, 52074 Aachen, Germany.
Jülich Aachen Research Alliance - BRAIN Institute 1: Structure Function Relationship, Jülich Aachen Research Alliance, 52425 Juelich, Germany.
Division of Psychology, Department of Clinical Neuroscience, Karolinska Institutet, 171 77 Stockholm, Sweden.
Stress Research Institute, Stockholm University, 106 91 Stockholm, Sweden.
Institute of Medical Psychology and Behavioral Immunobiology, Universitätsklinikum Essen, 45147 Essen, Germany.
Department of Psychology, Stockholm University, 106 91 Stockholm, Sweden.
Monell Chemical Senses Center, Philadelphia, PA 19104.
Department of Psychology, University of Pennsylvania, Philadelphia, PA 19104.


Throughout human evolution, infectious diseases have been a primary cause of death. Detection of subtle cues indicating sickness and avoidance of sick conspecifics would therefore be an adaptive way of coping with an environment fraught with pathogens. This study determines how humans perceive and integrate early cues of sickness in conspecifics sampled just hours after the induction of immune system activation, and the underlying neural mechanisms for this detection. In a double-blind placebo-controlled crossover design, the immune system in 22 sample donors was transiently activated with an endotoxin injection [lipopolysaccharide (LPS)]. Facial photographs and body odor samples were taken from the same donors when "sick" (LPS-injected) and when "healthy" (saline-injected) and subsequently were presented to a separate group of participants (n = 30) who rated their liking of the presented person during fMRI scanning. Faces were less socially desirable when sick, and sick body odors tended to lower liking of the faces. Sickness status presented by odor and facial photograph resulted in increased neural activation of odor- and face-perception networks, respectively. A superadditive effect of olfactory-visual integration of sickness cues was found in the intraparietal sulcus, which was functionally connected to core areas of multisensory integration in the superior temporal sulcus and orbitofrontal cortex. Taken together, the results outline a disease-avoidance model in which neural mechanisms involved in the detection of disease cues and multisensory integration are vital parts.


body odor; disease avoidance; endotoxin; lipopolysaccharide; sickness cues

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