Little is known about the biological mechanisms underlying childhood attachment. But now, scientists in Prof. Ofer Yizhar’s laboratory at the Weizmann Institute of Science have developed a noninvasive research method to investigate the role oxytocin has in shaping the social behavior of mice.
Once thought to simply promote sociability in adults, we now know that oxytocin can intensify emotions far removed from love, such as anxiety or aggression – and that the number of oxytocin receptors peaks during early childhood. Some studies have even linked oxytocin deficiency to childhood autism.
To shed light on the subject, a team led by Dr. Daniel Zelmanoff, a physician-scientist in Yizhar’s lab, developed a technique to encode a light-sensitive protein that, when exposed to light, “turns off” the nerve cell.
“This new method allows us to peek inside the brain without disturbing the [mouse] pups’ everyday lives,” Yizhar explains. “Our method lets us switch off the oxytocin system on demand, only during the exact situation we want to study.”
The researchers focused on oxytocin’s role during the temporary separation of a mouse pup from its mother and their reunion a few hours later. The scientists observed increased oxytocin activity in the pup’s brain during separation, which returned to normal after reunion. Pups with an active oxytocin system during the separation gradually adapted to being alone. In contrast, pups whose oxytocin system was silenced did not adapt. These findings show that oxytocin also plays a critical role in coping with loneliness.
In the next stage, the researchers explored whether oxytocin’s role differs between the sexes. They found that female pups with an active oxytocin system responded more when reunited with their mothers than females with silenced oxytocin systems, whereas the calls of male pups were unaffected by the status of their oxytocin systems. “This is the first sex difference observed in oxytocin system activity at such an early stage of development,” Yizhar notes. “It may offer a clue as to why males and females diverge in their social behaviors and emotional worlds long before puberty.”
“Most known functions of oxytocin are shared by all mammals,” Yizhar concludes. “Still, future studies must check whether the hormone affects the development of social behavior, emotional maturity, and maternal attachment in the brains of children. If so, this could help us better understand what can go wrong in emotional and social development – as in autism spectrum disorder, for example – and how to intervene at an early stage.”
