Evidence Found Of Human Brain Detection Of Pheromones
Pheromones are chemical signals secreted by one individual and received
by another individual of the same species, in which they trigger a
specific behavior or developmental process.Animals use such chemical signals to communicate messages ranging from attraction to aggression and territorial marking. One
of the classical hallmarks of pheromone signaling is that both
production of pheromones and the responses to them are gender specific.
There are many well-documented cases of pheromonal communication in
rodents and other mammals. One
of the hottest debates in the study of chemical senses is whether
humans can produce and detect pheromones, and if so, whether they can
use pheromone signaling to drive behavioral responses. The
strongest behavioral data supporting pheromone-based communication in
humans have come from work on menstrual synchrony. It has been shown,
for example, that female college roommates begin to menstruate at the
same time. Interestingly,
this synchronization effect may be achieved solely by wiping underarm
sweat from "donor" women onto the upper lips of "recipient" women,
strongly suggesting that human pheromones may be contained in sweat. But
there has been little to no evidence to date directly assaying how it
is that humans detect pheromonal signals. Furthermore, in other mammals
there is a separate accessory olfactory system that is the primary
pathway for processing pheromones, and there is only limited evidence
that this pathway functions in adult humans. Now
Ivanka Savic and colleagues at Stockholm's Huddinge University Hospital
have found definitive evidence for gender-specific activation of the
hypothalamus (a region of the brain that is known to be involved in
pheromone detection in rodents) in response to synthetic forms of
steroid hormones. The team
took PET scans of people smelling compounds closely related to both
testosterone and estrogen. PET scans measure the blood flow in
different regions of a subject's brain. They
found that an estrogen-like compound produced increased blood flow in
part of the hypothalamus in men, but not in women. Likewise, an
androgen related to testosterone produced increased blood flow in the
same part of the hypothalamus in women, but not in men. This
gender-specific activation of the hypothalamus is very different from
the pattern of brain activation observed in response to ordinary odors.
These results, which
convincingly demonstrate that the synthetic steroid hormones can act as
pheromonal signals and that the human brain is capable of detecting
them, are published in the August 30th issue of the journal Neuron. In a related preview in the same issue of Neuron,
Noam Sobel and Windy Brown of the University of California at Berkeley
discuss the Savic results in light of what is known about pheromonal
production and detection in other mammals, and outline the next
important questions in the study of human pheromonal communication.
[Contact: Ivanka Savic, Noam Sobel]
27-Aug-2001 |
