“What are Pheromones?” From Rishi Desai MD, of the Khan Academy.
He also did a great one on Olfaction:
These videos are presented here to help aid understanding, not to endorse any product.
Since humans don’t have an accessory olfactory epithelium or bulb, what is the mechanism by which we process pheromones? Do they still case signals to pass through the amygdala?
There was a project about a decade ago that was trying to figure out how pheromones are processed in humans. They think it’s the hypothalamus that gets activated when exposed to them, through the olfactory mucosa (I’ll have to keep reading how they followed up with that after 10 years)…
Brain response to putative pheromones in homosexual men. - PubMed - NCBI
"In a majority of animals, pheromone signals are transferred to the hypothalamus from the vomeronasal organ via the accessory olfactory nerve (5). Because our vomeronasal pit lacks neuronal connections to the brain (5, 6), the occurrence of pheromone transduction has long been questioned in humans. Several recent observations, however, suggest that this type of chemical communication cannot be ruled out. Sex steroid-derived compounds such as 4,16-androstadien-3-one (AND) and, less consistently, estra-1,3,5(10),16-tetraen-3-ol (EST) have been reported to induce sex-specific effects on the autonomic nervous system, mood, and context-dependent sexual arousal (7-12 ). The exact effects of AND and EST vary with the administered dose and experimental design, but, nevertheless, they seem to be sex-differentiated (especially with respect to AND), and thus to differ from the effects of ordinary odors. Studies with positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) have shown that smelling both AND and of EST activates the human brain (13-15), even in nonodorous concentrations (14, 15 ). AND is a derivative of testosterone and is primarily produced in male sweat (16), whereas EST is an estrogen-resembling steroid that has been detected in the urine of pregnant women (17). Male sweat has recently been reported to alter the pulsative hypothalamic release of luteinic hormone in females in an ovulation-promoting way (18). Thus, although it is premature to classify AND and EST as pheromones, the data suggest that they may function as chemosignals.
In a previous PET study of regional cerebral blood flow (rCBF) in heterosexual subjects (13), we found that smelling AND and EST caused a sex-differentiated activation of the anterior hypothalamus. In women, AND activated the preoptic area and ventromedial nuclei, whereas, in men, activation by EST involved an area covering the paraventricular and dorsomedial nuclei. In contrast, when men smelled AND and women EST, activations were found only in amygdala plus piriform cortex, anterior insular cortex, orbitofrontal cortex, and anterior cingulate cortex. These areas are reported to process the signals of common odors (19, 20, 21), and were possibly recruited by the odor components of AND and EST. Our interpretation of this sex-differentiated pattern of activation was that the two steroid compounds may act bimodally, both as pheromones and odors. We proposed the hypothesis that the anterior hypothalamus primarily processed signals from the pheromone-like component of AND and EST, whereas the olfactory brain primarily mediated the signals of their odor component. Depending on the sex of the responder in relation to the specific compound (AND or EST), one pathway dominated, whereas the other was suppressed. This hypothesis was based upon observations of a similar phenomenon in studies of other bimodal odorants (for example, acetone) (22)."
Very vivid video on the various original functions of Pheromones. Knowing better about it. BTW, the drawing is simple but convincing.
Great info here.