Newly discovered node in brain could help explain social communication disorders
Noise or sounds, such as a giggle, a cry, or a scream, and the emotional range it conveys is vital for effective social communication, said Dr. Lisa Stowers, a neuroscientist and professor at Scripps Research based in California, US. Most research on noise production in the brain has focused on language development, but identifying how the brain decides on these responses is the first step to understanding where things can go wrong in social behavioural disorders such as autism and depression.
A group of scientists, led by Scripps Research, have just discovered a node in the brains of male mice that modulates the sounds they make in social situations – it could help identify similar locations in the human brain so as to be prepared for when human behaviour goes awry. “It’s giving us clues to how information is organised in the brain, and how different features of information can be separated out in different brain regions,” said Stowers.
Usually, male mice produce complicated whistles or “songs” as part of their courtship behaviour; these are too high for the human ear to detect, are louder and longer when the female mouse is nearby or when her scent is stronger.
The scientistsquickly identified a specific type of neuron in a part of the hypothalamus called the lateral preoptic area that controls the emotional regulation of these sounds, and by directly stimulating the right nodes from these neurons, could trigger the whole array of noises that go into a mouse song. Varying the level of stimulation allowed them to control how enthusiastic those sounds were.
“The hypothalamus and the rest of the limbic system control body functions such as hunger, thirst and temperature regulation, as well as the basic features of emotional behaviour like sex and fear,” Stowers explained. “It is fitting that the emotional aspect of these social noises are generated in this region of the brain.”
When the scientists blocked these nodes, male mice encountering a female would attempt to court her in silence (female mice responded by kicking the males and running away). If they then bypassed these nodes and activated the next node downstream, the male mice only made long, loud noises.
“They’re basically just shouting, but finding these neurons tells us that this part of the brain is doing this emotional scaling and persistence. If you take that away, then you lose all of that affect, all of that emotional range, and the ability to have effective social communication.”
“We are starting to get a detailed look at where in the brain different types of computations are being made. Now that we know that this simple behaviour is regulated in the hypothalamus, we can study whether others behaviours are also using similar circuits and if so, perhaps find a common mechanism—and drug target—for when emotions are not generated appropriately,” Stowers concluded.
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