| 1. |
- Sarolidou, Georgia, et al.
(författare)
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Emotional expressions of the sick face
- 2019
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Ingår i: Brain, behavior, and immunity. - : Elsevier BV. - 0889-1591 .- 1090-2139. ; 80, s. 286-291
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Tidskriftsartikel (refereegranskat)abstract
- To handle the substantial threat posed by infectious diseases, behaviors that promote avoidance of contagion are crucial. Based on the fact that sickness depresses mood and that emotional expressions reveal inner states of individuals to others, which in turn affect approach/avoidance behaviors, we hypothesized that facial expressions of emotion may play a role in sickness detection. Using an experimental model of sickness, 22 volunteers were intravenously injected with either endotoxin (lipopolysaccharide; 2 ng/kg body weight) and placebo using a randomized cross-over design. The volunteers were two hours later asked to keep a relaxed expression on their face while their facial photograph was taken. To assess the emotional expression of the sick face, 49 participants were recruited and were asked to rate the emotional expression of the facial photographs of the volunteers when sick and when healthy. Our results indicate that the emotional expression of faces changed two hours after being made temporarily sick by an endotoxin injection. Sick faces were perceived as more sick/less healthy, but also as expressing more negative emotions, such as sadness and disgust, and less happiness and surprise. The emotional expressions mediated 59.1% of the treatment-dependent change in rated health. The inclusion of physical features associated with emotional expressions to the mediation analysis supported these results. We conclude that emotional expressions may contribute to detection and avoidance of infectious individuals and thereby be part of a behavioral defense against disease.
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| 2. |
- Axelsson, John, et al.
(författare)
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Identification of acutely sick people and facial cues of sickness
- 2018
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Ingår i: Proceedings of the Royal Society of London. Biological Sciences. - : The Royal Society. - 0962-8452 .- 1471-2954. ; 285:1870
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Tidskriftsartikel (refereegranskat)abstract
- Detection and avoidance of sick individuals have been proposed as essential components in a behavioural defence against disease, limiting the risk of contamination. However, almost no knowledge exists on whether humans can detect sick individuals, and if so by what cues. Here, we demonstrate that untrained people can identify sick individuals above chance level by looking at facial photos taken 2 h after injection with a bacterial stimulus inducing an immune response (2.0 ng kg-1 lipopolysaccharide) or placebo, the global sensitivity index being d' = 0.405. Signal detection analysis (receiver operating characteristic curve area) showed an area of 0.62 (95% confidence intervals 0.60-0.63). Acutely sick people were rated by naive observers as having paler lips and skin, a more swollen face, droopier corners of the mouth, more hanging eyelids, redder eyes, and less glossy and patchy skin, as well as appearing more tired. Our findings suggest that facial cues associated with the skin, mouth and eyes can aid in the detection of acutely sick and potentially contagious people.
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| 3. |
- Lasselin, Julie, et al.
(författare)
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Lipopolysaccharide Alters Motivated Behavior in a Monetary Reward Task : a Randomized Trial
- 2017
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Ingår i: Neuropsychopharmacology. - : Springer Science and Business Media LLC. - 0893-133X .- 1740-634X. ; 42:4, s. 801-810
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Tidskriftsartikel (refereegranskat)abstract
- Inflammation-induced sickness is associated with a large set of behavioral alterations; however, its motivational aspects remain poorly explored in humans. The present study assessed the effect of lipopolysaccharide (LPS) administration at a dose of 2 ng/kg of body weight on motivation in 21 healthy human subjects in a double-blinded, placebo (saline)-controlled, cross-over design. Incentive motivation and reward sensitivity were measured using the Effort Expenditure for Rewards Task (EEfRT), in which motivation for high-effort/high-reward trials vs low-effort/low-reward trials are manipulated by variations in reward magnitude and,probability to win. Because of the strong interactions between sleepiness and motivation, the role of sleepiness was also determined. As expected, the probability to win predicted the choice to engage in high-effort/high-reward trials; however, this occurred at a greater extent after LPS than after saline administration. This effect was related to the level of sleepiness. Sleepiness increased motivation to choose the high-effort/high-reward mode of response, but only when the probability to win was the highest. LPS had no effect on reward sensitivity either directly or via sleepiness. These results indicate that systemic inflammation induced by LPS administration causes motivational changes in young healthy subjects, which are associated with sleepiness. Thus, despite its association with energy-saving behaviors, sickness allows increased incentive motivation when the effort is deemed worthwhile.
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| 4. |
- Lasselin, Julie, et al.
(författare)
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Sleep during naturally occurring respiratory infections : A pilot study
- 2019
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Ingår i: Brain, behavior, and immunity. - : Elsevier BV. - 0889-1591 .- 1090-2139. ; 79, s. 236-243
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Tidskriftsartikel (refereegranskat)abstract
- There is strong experimental support that infections increase the drive for sleep in animals, and it is widely believed that more sleep is part of an adaptive immune response. While respiratory infections (RI) are very prevalent in humans, there is a striking lack of systematic knowledge on how it affects sleep. We recruited 100 people, among whom 28 became sick with an RI during the study period (fulfilling criteria for influenza-like illness, ILI, or acute respiratory infection, ARI). We measured sick participants' sleep at home, both objectively (actigraphy) and subjectively (diary ratings), for one week as well as four weeks later when healthy. During the week with RI, people spent objectively longer time in bed and had a longer total sleep time compared to the healthy week. During the infection, participants also had more awakenings, but no significant differences in sleep latency or sleep efficiency. While sick, people also reported increased difficulties falling asleep, worse sleep quality, more restless sleep and more shallow sleep, while they did not report sleep to be less sufficient. Most problems occurred at the beginning of the sickness week, when symptoms were strong, and showed signs of recovery thereafter (as indicated by interactions between condition and day/night of data collection for all the 10 sleep outcomes). The degree of symptoms of RI was related to a worse sleep quality and more restless sleep, but not to any of the objective sleep outcomes or the other subjective sleep variables. Having a higher body temperature was not significantly related to any of the sleep variables. This study suggests that having a respiratory infection is associated with spending more time in bed and sleeping longer, but also with more disturbed sleep, both objectively and subjectively. This novel study should be seen as being of pilot character. There is a need for larger studies which classify pathogen type and include baseline predictors, or that manipulate sleep, in order to understand whether the sleep alterations seen during infections are adaptive and whether sleep interventions could be used to improve recovery from respiratory infections.
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| 5. |
- Arshamian, Artin, et al.
(författare)
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Human sickness detection is not dependent on cultural experience
- 2021
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Ingår i: Proceedings of the Royal Society of London. Biological Sciences. - : The Royal Society. - 0962-8452 .- 1471-2954. ; 288:1954
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Tidskriftsartikel (refereegranskat)abstract
- Animals across phyla can detect early cues of infection in conspecifics, thereby reducing the risk of contamination. It is unknown, however, if humans can detect cues of sickness in people belonging to communities with whom they have limited or no experience. To test this, we presented Western faces photographed 2 h after the experimental induction of an acute immune response to one Western and five non-Western communities, including small-scale hunter-gatherer and large urban-dwelling communities. All communities could detect sick individuals. There were group differences in performance but Western participants, who observed faces from their own community, were not systematically better than all non-Western participants. At odds with the common belief that sickness detection of an out-group member should be biased to err on the side of caution, the majority of non-Western communities were unbiased. Our results show that subtle cues of a general immune response are recognized across cultures and may aid in detecting infectious threats.
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| 6. |
- Balter, Leonie J. T., et al.
(författare)
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Lipopolysaccharide-induced changes in the kynurenine pathway and symptoms of sickness behavior in humans
- 2023
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Ingår i: Psychoneuroendocrinology. - 0306-4530 .- 1873-3360. ; 153
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Tidskriftsartikel (refereegranskat)abstract
- Metabolites of the kynurenine pathway are hypothesized to be implicated in inflammation-associated depression, but there is a lack of experimental studies in humans assessing the kinetics of kynurenine metabolites in relation to experimentally-induced sickness. The aim of the present study was to assess changes in the kynurenine pathway and to explore its relation to symptoms of sickness behavior during an acute experimental immune challenge.This double-blind placebo-controlled randomized cross-over study included 22 healthy human participants (n = 21 both sessions, Mage = 23.4, SD = 3.6, nine women) who received an intravenous injection of 2.0 ng/kg lipopolysaccharide (LPS) and saline (placebo) on two different occasions in a randomized order. Blood samples (0 h, 1 h, 1.5 h, 2 h, 3 h, 4 h, 5 h, 7 h post-injection) were analyzed for kynurenine metabolites and inflammatory cytokines. The intensity of symptoms of sickness behavior was assessed using the 10-item Sickness Questionnaire at 0 h, 1.5 h, 3 h, 5 h, and 7 h post-injection.LPS induced significantly lower concentrations of plasma tryptophan (at 2 h, 4 h, 5 h, and 7 h post-injection), kynurenine (at 2 h, 3 h, 4 h, and 5 h post-injection), nicotinamide (at 4 h, 5 h, and 7 h post-injection), and higher levels for quinolinic acid at 5 h post-injection as compared to placebo. LPS did not affect kynurenic acid, 3-hydroxykynurenine, and picolinic acid. The development of the sickness symptoms was largely similar across items, with the highest levels around 1.5–3 h post-injection. Changes in plasma levels of kynurenine metabolites seem to coincide rather than precede or follow changes in subjective sickness. Exploratory analyses indicate that higher Sickness Questionnaire total scores at 1.5–5 h post-injection were correlated with lower kynurenic acid and nicotinamide levels.These results lend further support for LPS-induced changes in the kynurenine pathway, but may not, as interpreted from blood levels, causally link to LPS-induced acute symptoms of sickness behavior. Future research may consider a larger sample to further scrutinize the role of the kynurenine pathway in the sickness response.
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| 7. |
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| 8. |
- Gordon, Amy R., et al.
(författare)
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Detection of Inflammation via Volatile Cues in Human Urine
- 2018
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Ingår i: Chemical Senses. - : Oxford University Press (OUP). - 0379-864X .- 1464-3553. ; 43:9, s. 711-719
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Tidskriftsartikel (refereegranskat)abstract
- Contagious disease is a major threat to survival, and the cost of relying on the immune system to defeat pathogens is high; therefore, behavioral avoidance of contagious individuals is arguably an adaptive strategy. Animal findings demonstrate the ability to detect and avoid sick individuals by the aid of olfactory cues, and a recent study indicated that human axillary odor also becomes more aversive as a function of immune activation. By injecting healthy human participants with lipopolysaccharide (0.6 ng/kg body weight) to experimentally induce inflammation, this study demonstrates that natural daily rhythms of urine odor-its perceived dimensions and volatile profile-are altered within hours of inflammation onset. Whereas healthy human urine decreases in averseness over the course of a single day, inflammation interrupts this process and results in an increased urine odor averseness and an altered volatile composition. These results support the notion that subtle and early cues of sickness may be detected and avoided, thereby complementing the immune system in its role of keeping us alive and healthy.
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| 9. |
- Gordon, Amy R., et al.
(författare)
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Human scent as a first-line defense against disease
- 2023
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Ingår i: Scientific Reports. - : Springer Nature. - 2045-2322. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- Individuals may have a different body odor, when they are sick compared to healthy. In the non-human animal literature, olfactory cues have been shown to predict avoidance of sick individuals. We tested whether the mere experimental activation of the innate immune system in healthy human individuals can make an individuals' body odor be perceived as more aversive (intense, unpleasant, and disgusting). Following an endotoxin injection (lipopolysaccharide; 0.6 ng/kg) that creates a transient systemic inflammation, individuals smelled more unpleasant compared to a placebo group (saline injection). Behavioral and chemical analyses of the body odor samples suggest that the volatile components of samples from sick individuals changed qualitatively rather than quantitatively. Our findings support the hypothesis that odor cues of inflammation in axillary sweat are detectable just a few hours after experimental activation of the innate immune system. As such, they may trigger behavioral avoidance, hence constituting a first line of defense against pathogens of infected conspecifics.
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| 10. |
- Gordon, Amy R., et al.
(författare)
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The scent of disease
- 2015
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Ingår i: Chemical Senses. - : Oxford University Press (OUP). - 0379-864X .- 1464-3553. ; 40:3, s. 254-254
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Tidskriftsartikel (refereegranskat)abstract
- Ability to detect diseases in conspecifics would be advantageous for the individual. In line with this, rodents avoid body odors of infected individuals. Two studies (Olsson et al. 20014; in prep.) indicated that this is possible by way of human smell and human observers. T-shirts from donors (worn for 4 hours) that had received an injection of endotoxin [0.8ng lipopolysaccharide (LPS) / kg body weight], which causes systemic inflammation, smelled more unpleasant, intense, and sick than shirts from donors that had received a placebo (Saline) injection. GC/MS analysis of the shirts suggested that the change of body odor was not due to a general increase of odorous compounds in the “sick shirts” compared to “placebo shirts” but rather to a qualitative change. Study 2 (ongoing) further investigated the nature of this perception. In a first experiment, we compared the body odor of 30 endotoxin (0.6ng LPS / kg body weight) and 21 placebo (Saline) donors. Again, body odors were sampled during 4 hours using T-shirts. Observers then smelled the shirts and rated intensity, pleasantness, and disgust. In a second experiment, urine from these donors were collected and was investigated in the same way with subjective ratings. Altogether the data suggest that systemic inflammation makes body odors more aversive within a few hours.
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