By Penny Stern, MD
NEW YORK, Jun 26 (Reuters Health) - "The very thought of you," begins an old
love song. But scientifically inquiring minds want to know: How do you form a
memory of a loved one, or any other person that you meet? Social memory--that
is, recognizing those you've seen before--is obviously a critical component of
interacting with other people and forming relationships. US researchers now
report that this type of memory is controlled by a gene.
Specifically, social memory seems to be related to having a functioning gene
for the production of oxytocin, a hormone manufactured in the brain, according
to a report in the July issue of Nature Genetics.
Oxytocin is perhaps best known for its roles in childbirth and lactation,
but studies in animals have shown that it also plays a role in pair bonding and
mate-guarding. The hormone is found in all mammals, including humans.
Senior study author Dr. James T. Winslow from the Emory University School of
Medicine in Atlanta, Georgia, and colleagues, explain that so-called 'knock-out'
mice who lacked the gene for oxytocin "failed to develop social memory, whereas
wild-type (oxytocin-producing) mice showed intact social memory."
For mice and other rodents, their sense of smell works in concert with the
other senses enabling the animals to become familiar with their environment and
recognize elements in it.
The research team proved definitively that the apparent problem with social
memory in the mice did not originate in an olfactory (smell) defect since the
knock-out mice were able to find hidden food as successfully as the mice with
oxytocin genes.
Other experiments confirmed that the knock-out mice were able to master
mazes with as much skill as the normal mice, demonstrating that they had no
problems with spatial memory.
To determine whether social memory could be artificially induced in the
mice, Winslow and his team gave oxytocin to the animals. "Administration of
(oxytocin) completely rescued social memory in (knock-out) mice," they write.
And how might these findings apply to people? Winslow told Reuters Health
that "oxytocin receptors are found in human limbic and forebrain structures
associated with emotional behavior. So oxytocin is a good candidate for studies
of the neural systems involved in the development of social attachments in
humans."
He pointed out that diseases "such as schizophrenia and autism are
characterized by difficulties developing normal social relationships" which
suggest that oxytocin and related proteins may "represent intriguing candidates
for treatment research."
Winslow emphasized that though his team's findings are exciting, "it is also
very early in the process of understanding how the mammalian brain influences,
and is influenced by, social information and how (oxytocin) contributes to this
relationship."
For the time being, it is clear that oxytocin "is necessary for the normal
development of social memory in mice (supporting) the hypothesis that social
memory has a neural basis distinct from other forms of memory," the study
authors conclude.
