Human Gender Differences in the Perception of Conspecific Alarm Chemosensory Cues

Abstract

It has previously been established that, in threatening situations, animals use alarm pheromones to communicate danger. There is emerging evidence of analogous chemosensory “stress” cues in humans. For this study, we collected alarm and exercise sweat from “donors,” extracted it, pooled it and presented it to 16 unrelated “detector” subjects undergoing fMRI. The fMRI protocol consisted of four stimulus runs, with each combination of stimulus condition and donor gender represented four times. Because olfactory stimuli do not follow the canonical hemodynamic response, we used a model-free approach. We performed minimal preprocessing and worked directly with block-average time series and step-function estimates. We found that, while male stress sweat produced a comparably strong emotional response in both detector genders, female stress sweat produced a markedly stronger arousal in female than in male detectors. Our statistical tests pinpointed this gender-specificity to the right amygdala (strongest in the superficial nuclei). When comparing the olfactory bulb responses to the corresponding stimuli, we found no significant differences between male and female detectors. These imaging results complement existing behavioral evidence, by identifying whether gender differences in response to alarm chemosignals are initiated at the perceptual versus emotional level. Since we found no significant differences in the olfactory bulb (primary processing site for chemosensory signals in mammals), we infer that the specificity in responding to female fear is likely based on processing meaning, rather than strength, of chemosensory cues from each gender.

Gender Differences in Electroencephalographic Activity in Response to the Earthy Odorants Geosmin and 2-Methylisoborneol

“…Those studies found that women and men showed different EEG activity under various conditions [32][33][34]. Radulescu and Mujica-Parodi [35] stated that women have a better olfactory sensation than men in many species and differences in their sensitivity may be based on biological meanings. Recently, Haehner et al [36] reported that women easily identified different fragrances (orange, lime, and lemon) and changed their behavior accordingly when compared to men.…”

Social Fear Learning: from Animal Models to Human Function

“…Rodent studies demonstrate that SFL in infant rats occurs through chemosignalling pathways [27, 33]. It has not been determined whether alarm chemosignaling plays a role in human infants, although recent studies suggest that olfaction may mediate social fear transmission in adults [72, 73]. Interestingly, research shows that infant SFL may occur without any increased activation of the ACC or the insular cortex which are not fully functional until later in life [33].…”

Trpc2 pseudogenization dynamics in bats reveal ancestral vomeronasal signaling, then pervasive loss

“…In mice, for example, some pheromone receptors may also be present in the main olfactory epithelium (Omura and Mombaerts 2014;Kanageswaran et al 2015), possibly explaining why some apparently pheromone-mediated behavior is maintained in species lacking the vomeronasal organ. Finally, the debate on whether humans are capable of detecting pheromones is still far from resolved, as anatomical advances are ongoing Wessels et al 2014;Vasuki et al 2016), and behavioral experiments suggest that we can perceive conspecific chemosensory cues (Radulescu and Mujica-Parodi 2013;Lübke and Pause 2015;Gelstein et al 2011). Finally, the debate on whether humans are capable of detecting pheromones is still far from resolved, as anatomical advances are ongoing Wessels et al 2014;Vasuki et al 2016), and behavioral experiments suggest that we can perceive conspecific chemosensory cues (Radulescu and Mujica-Parodi 2013;Lübke and Pause 2015;Gelstein et al 2011).…”

“…While Trpc2 has been pseudogenized in the harbor seal and river otter (Yu et al 2010), both species retain a well-developed main olfactory system and behavioral studies indicate the presence of some olfactory social communication (van Valkenburgh et al 2011;Stoffel et al 2015). Finally, the debate on whether humans are capable of detecting pheromones is still far from resolved, as anatomical advances are ongoing Wessels et al 2014;Vasuki et al 2016), and behavioral experiments suggest that we can perceive conspecific chemosensory cues (Radulescu and Mujica-Parodi 2013;Lübke and Pause 2015;Gelstein et al 2011).…”