Hormone important in recognizing familiar faces

Oxytocin, a hormone involved in child-birth and breast-feeding, helps people recognize familiar faces, according to new research in the January 7 issue of The Journal of Neuroscience. Study participants who had one dose of an oxytocin nasal spray showed improved recognition memory for faces, but not for inanimate objects.

“This is the first paper showing that a single dose of oxytocin specifically improves recognition memory for social, but not for nonsocial, stimuli,” said Ernst Fehr, PhD, an economist at the University of Zurich who has studied oxytocin’s effect on trust and is unaffiliated with the new study. “The results suggest an immediate, selective effect of the hormone: strengthening neuronal systems of social memory,” Fehr said.

In mice, oxytocin has been shown to be important in social recognition — remembering that another mouse is familiar. Unlike humans, who use visual cues, mice use smell to recognize and distinguish other mice.

In humans, oxytocin increases social behaviors like trust, but its role in social memory has been unclear. “Recognizing a familiar face is a crucial feature of successful social interaction in humans,” said Peter Klaver, PhD, at the University of Zurich, the senior author of the new study, which was led by Ulrike Rimmele, PhD, at New York University. “In this study, we investigated for the first time the systematic effect of oxytocin on social memory in humans,” Klaver said.

Klaver and colleagues had study participants use a nasal spray containing either oxytocin or a placebo and then showed them images of faces and inanimate objects, including houses, sculptures, and landscapes. Participants were given a surprise test when they returned the next day — they were shown some of the images they had seen the day before as well as some new ones and were asked to distinguish between images that were “new,” images that they specifically “remembered” being presented, and images they recognized (”knew”) as familiar but could not recall the presentation context.

Volunteers who used the oxytocin spray more accurately recognized the faces they had seen before than did those in the placebo group. However, the two groups did not differ in recognizing the other, nonsocial images, suggesting that oxytocin specifically improved social memory and that different mechanisms exist for social and nonsocial memory. Further analysis showed that oxytocin selectively improved the discrimination of new and familiar faces — participants with oxytocin were less likely to mistakenly characterize unfamiliar faces as familiar. “Together, our data indicate that oxytocin in humans immediately strengthens the capability to correctly recognize and discriminate faces,” Klaver said.

“The study highlights the parallels in social information processing in mice and man, and adds further support to the notion that oxytocin plays a critical role,” said Larry Young, PhD, at Emory University, an expert on oxytocin who is unaffiliated with the current study. “This has important implications for disorders such as autism, where social information processing is clearly impaired,” Young said.

Source : http://www.sfn.org/

Scientists discover an ancient odor-detecting mechanism in insects

In 1913 Theodore Roosevelt added cartographer to his resume when he and his crew ventured up an unspeakably dangerous and uncharted tributary named the River of Doubt. Now, on a charting expedition of their own, Rockefeller University scientists have completed a journey that has also defied expectation. In work to be published in the January 9 issue of Cell, the team reports the discovery of a new family of receptors in the fly nose, a finding that not only fills in a missing piece in the organizational logic of the insect olfactory system but also unearths one of the most ancient mechanisms that organisms have evolved to smell.

Vosshall, head of the Laboratory of Neurogenetics and Behavior, revamps traditional ideas regarding the roles of ionotropic glutamate receptors, proteins that reside deep in the brain at the synapses. There, they grab glutamate molecules and quickly relay messages from one nerve cell to the next, helping animals learn, move and remember. But Vosshall’s group now shows that insects do not relegate these receptors to the depths of the brain. They also put them to use elsewhere: in the nose.

“On the surface it’s a completely absurd idea,” says Vosshall, who is also a Howard Hughes Medical Institute investigator. “We know what these proteins do; they sit at the synapse and mediate fast neuronal communication. So the idea that the fly has massively expanded the number of these receptors and positioned them to interact with small molecules in the air seems very strange. But if you think about it, it makes sense. The process is the same, but rather than grabbing small molecules at the synapse, they’re grabbing small molecules from the air.”

The project began two years ago, when Vosshall and Richard Benton, then a postdoc in her lab, noticed a group of six ionotropic glutamate receptor genes while sifting through the fly genome. Although this group was recognized 10 years ago, ever since the genome was sequenced, the genes did not have a known function, in part because it was assumed they must be similar to any other ionotropic glutamate receptor deep in the fly brain. But to Vosshall and Benton, who is now at the Center for Integrative Genomics in Lausanne, Switzerland, that didn’t matter.

Vosshall and her team wondered whether these receptors could in fact represent the “missing” receptors thought to exist in the fly’s “nose” — its two antennae. Each antenna is divided into three types of smell neurons. Scientists have characterized the receptors that detect odors in two of these types but those receptors were mysteriously absent in the third, a swath of territory known as the coeloconic sensilla. “It has been shown that cells in the coeloconic sensilla detect odors,” Vosshall says. “It’s just that we didn’t know how they did it.”

The team showed that these receptors, which the Vosshall lab named ionotropic receptors, do in fact explain how cells in coeloconic sensilla detect odors. First, they showed that they are expressed in complex combinatorial patterns at the sensory end of olfactory neurons where they have access to and can scan the outside world for odors. They then showed that when these receptors are expressed in the cells in the coeloconic sensilla, the cells respond to odors. Finally, the researchers showed that when they plucked a receptor — say one that detects an odor that resembles a mix of grass and honey — out of its native cell and genetically embedded it in a different cell, the new cell would now detect that odor.

Although it is still unclear why insects have developed two sets of chemosensory receptors — olfactory receptors and ionotropic receptors — the work raises questions regarding their evolutionary origin. Ten years ago, researchers at New York University revealed that plants, which detect soil nutrients and chemicals in the air, also express glutamate receptors, suggesting that the ancestral origin of glutamate receptors may have been to detect small molecules in the air, rather than small molecules in the brain.

“In a way, these receptors were very well hidden because everyone assumed that they were extra glutamate receptors that were unlikely to be of interest,” explains Vosshall. “All we did to find them was searched for a gene family of unknown function — and left our preconceived notions aside.”

Source : http://www.rockefeller.edu/