Limits...
Chemosensory cues to conspecific emotional stress activate amygdala in humans.

Mujica-Parodi LR, Strey HH, Frederick B, Savoy R, Cox D, Botanov Y, Tolkunov D, Rubin D, Weber J - PLoS ONE (2009)

Bottom Line: In an fMRI experiment and its replication, we showed that scanned participants showed amygdala activation in response to samples obtained from donors undergoing an emotional, but not physical, stressor.An odor-discrimination experiment suggested the effect was primarily due to emotional, and not odor, differences between the two stimuli.A fourth experiment investigated behavioral effects, demonstrating that stress samples sharpened emotion-perception of ambiguous facial stimuli.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Engineering, Stony Brook University School of Medicine, Stony Brook, New York, United States of America. lmujicaparodi@gmail.com

ABSTRACT
Alarm substances are airborne chemical signals, released by an individual into the environment, which communicate emotional stress between conspecifics. Here we tested whether humans, like other mammals, are able to detect emotional stress in others by chemosensory cues. Sweat samples collected from individuals undergoing an acute emotional stressor, with exercise as a control, were pooled and presented to a separate group of participants (blind to condition) during four experiments. In an fMRI experiment and its replication, we showed that scanned participants showed amygdala activation in response to samples obtained from donors undergoing an emotional, but not physical, stressor. An odor-discrimination experiment suggested the effect was primarily due to emotional, and not odor, differences between the two stimuli. A fourth experiment investigated behavioral effects, demonstrating that stress samples sharpened emotion-perception of ambiguous facial stimuli. Together, our findings suggest human chemosensory signaling of emotional stress, with neurobiological and behavioral effects.

Show MeSH

Related in: MedlinePlus

On Likert Scales, participants rated both conditions as mild and neutral; there were no significant differences between their ratings between conditions.A separate forced-choice discrimination experiment additionally indicated that participants were unable to distinguish between the two odors. Together, these suggest that the amygdala activation seen in response to the STRESS, but not EXERCISE, sweat was due to engagement of emotional processing rather than perception of distinct odors.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2713432&req=5

pone-0006415-g004: On Likert Scales, participants rated both conditions as mild and neutral; there were no significant differences between their ratings between conditions.A separate forced-choice discrimination experiment additionally indicated that participants were unable to distinguish between the two odors. Together, these suggest that the amygdala activation seen in response to the STRESS, but not EXERCISE, sweat was due to engagement of emotional processing rather than perception of distinct odors.

Mentions: While the fMRI experiments indicate that participants' amygdala were able to distinguish between the sweat of stressed and non-stressed colleagues, it was important to establish whether this activation might be attributable to odor differences between the two conditions [31], [32]. As shown in Figure 4, subjects rated both odors, using Likert scales ranging from zero (“undetectable”/“pleasant”) to ten (“very strong”/“unpleasant”) as equivalently mild (Stress: μ = 2.6, s.d. = 2.3, Exercise: μ = 2.6, s.d. = 2.3; Wilcoxon sign-ranks test: Z = 1.11, p = 0.28, N = 26) and neutral (Stress: μ = 4.5, s.d. = 1.1, Exercise: μ = 4.8, s.d. = 0.8; Wilcoxon sign-ranks test: Z = 1.56, p = 0.12, N = 26). To investigate whether the conditions had odors that were qualitatively distinct, we also conducted a double-blind forced-choice odor discrimination experiment, in which 16 participants (50% female) identified whether 16 test and control pairs (50% different), randomly presented, were identical or different; participant ratings were not significantly different than chance (one-sample t-test: t = 0.64, p = 0.53, N = 16). The data suggest that participants were not able to consciously distinguish between test and control odors, and therefore rule out simple odor discrimination as an explanation for amygdala activation in response to the STRESS−EXERCISE contrast.


Chemosensory cues to conspecific emotional stress activate amygdala in humans.

Mujica-Parodi LR, Strey HH, Frederick B, Savoy R, Cox D, Botanov Y, Tolkunov D, Rubin D, Weber J - PLoS ONE (2009)

On Likert Scales, participants rated both conditions as mild and neutral; there were no significant differences between their ratings between conditions.A separate forced-choice discrimination experiment additionally indicated that participants were unable to distinguish between the two odors. Together, these suggest that the amygdala activation seen in response to the STRESS, but not EXERCISE, sweat was due to engagement of emotional processing rather than perception of distinct odors.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2713432&req=5

pone-0006415-g004: On Likert Scales, participants rated both conditions as mild and neutral; there were no significant differences between their ratings between conditions.A separate forced-choice discrimination experiment additionally indicated that participants were unable to distinguish between the two odors. Together, these suggest that the amygdala activation seen in response to the STRESS, but not EXERCISE, sweat was due to engagement of emotional processing rather than perception of distinct odors.
Mentions: While the fMRI experiments indicate that participants' amygdala were able to distinguish between the sweat of stressed and non-stressed colleagues, it was important to establish whether this activation might be attributable to odor differences between the two conditions [31], [32]. As shown in Figure 4, subjects rated both odors, using Likert scales ranging from zero (“undetectable”/“pleasant”) to ten (“very strong”/“unpleasant”) as equivalently mild (Stress: μ = 2.6, s.d. = 2.3, Exercise: μ = 2.6, s.d. = 2.3; Wilcoxon sign-ranks test: Z = 1.11, p = 0.28, N = 26) and neutral (Stress: μ = 4.5, s.d. = 1.1, Exercise: μ = 4.8, s.d. = 0.8; Wilcoxon sign-ranks test: Z = 1.56, p = 0.12, N = 26). To investigate whether the conditions had odors that were qualitatively distinct, we also conducted a double-blind forced-choice odor discrimination experiment, in which 16 participants (50% female) identified whether 16 test and control pairs (50% different), randomly presented, were identical or different; participant ratings were not significantly different than chance (one-sample t-test: t = 0.64, p = 0.53, N = 16). The data suggest that participants were not able to consciously distinguish between test and control odors, and therefore rule out simple odor discrimination as an explanation for amygdala activation in response to the STRESS−EXERCISE contrast.

Bottom Line: In an fMRI experiment and its replication, we showed that scanned participants showed amygdala activation in response to samples obtained from donors undergoing an emotional, but not physical, stressor.An odor-discrimination experiment suggested the effect was primarily due to emotional, and not odor, differences between the two stimuli.A fourth experiment investigated behavioral effects, demonstrating that stress samples sharpened emotion-perception of ambiguous facial stimuli.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Engineering, Stony Brook University School of Medicine, Stony Brook, New York, United States of America. lmujicaparodi@gmail.com

ABSTRACT
Alarm substances are airborne chemical signals, released by an individual into the environment, which communicate emotional stress between conspecifics. Here we tested whether humans, like other mammals, are able to detect emotional stress in others by chemosensory cues. Sweat samples collected from individuals undergoing an acute emotional stressor, with exercise as a control, were pooled and presented to a separate group of participants (blind to condition) during four experiments. In an fMRI experiment and its replication, we showed that scanned participants showed amygdala activation in response to samples obtained from donors undergoing an emotional, but not physical, stressor. An odor-discrimination experiment suggested the effect was primarily due to emotional, and not odor, differences between the two stimuli. A fourth experiment investigated behavioral effects, demonstrating that stress samples sharpened emotion-perception of ambiguous facial stimuli. Together, our findings suggest human chemosensory signaling of emotional stress, with neurobiological and behavioral effects.

Show MeSH
Related in: MedlinePlus