Brain switch in voles makes them fall in love at first sight

31 May 2017
 
By Andy Coghlan

Talk about flipping a switch. By simply activating certain circuits in the brains of female prairie voles, researchers made them “fall in love” with specific males.

“It’s like remote control of the brain circuitry to create a pair bond,” says Robert Liu at Emory University in Atlanta, Georgia, and a member of the team using technology to play Eros.

The team chose to study pair-bonding in prairie voles because they are one of the few species that mate for life. “Pair-bonding in voles is not exactly the same as in people, but we believe that it likely shares many of the underlying neural mechanisms as falling in love in humans,” says Liu.
 
As a first test, the researchers implanted electrodes into the brains of females to identify the circuitry activated when they naturally formed a pair bond and mated. They found that connections in a specific circuit became stronger, especially after mating, and whenever the pair huddled together.

“We discovered that rhythmic oscillations of groups of neurons in the prefrontal cortex – an area of the brain involved in decision-making and executive functions – controlled the strength of oscillations in neurons of the neighbouring nucleus accumbens, an area involved in pleasure, reward and addiction,” says Liu.

The upshot, he says, is that physical features of the male, such as his odours and vocalisations, become stamped into the reward system, meaning partners become “rewards” in themselves. 

 
Activating the love circuit
Once they had identified the “love” circuit, the researchers devised a way to activate it themselves in female voles using a technique called optogenetics.

To do this, they inserted genes into neurons of the prefrontal cortex that would turn the neurons on when exposed to light. They then fed pulses of light into that brain region through a fine optical fibre to activate the genes.

To test whether the technique could make a female fall in love, they first put a lucky male in close proximity to her for a bonding period of around an hour, but without allowing them to mate.



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