Researchers at Duke Uni­ver­si­ty have iso­lat­ed a clus­ter of neu­rons in a mouse’s brain that are cru­cial to mak­ing the squeaky, ultra­son­ic ‘songs’ a male mouse pro­duces when court­ing a poten­tial mate.

In fact, they now under­stand these neu­rons well enough to be able to make a mouse sing on com­mand or to silence it so that it can’t sing, even when it wants to impress a mate.

This lev­el of under­stand­ing and con­trol is a key advance­ment in the ongo­ing search for the mech­a­nisms that allow humans to form speech and oth­er com­mu­ni­ca­tion sounds. The researchers are broad­ly inter­est­ed in the brain’s pro­duc­tion of speech and have worked with song­birds and mice as mod­els for humans.

“We were inter­est­ed in under­stand­ing how mice pro­duce these ‘love songs,’ as we call them in the lab,” said Kather­ine Tschi­da, who led the research as a post-doc­tor­al fel­low in both the Richard Mooney and Fan Wang labs at Duke neu­ro­bi­ol­o­gy.

For this study, Tschi­da and her col­leagues focused on a part of the mid­brain called the peri­aque­duc­tal gray, or PAG for short, because they knew from pre­vi­ous work by oth­ers that it would be a key play­er in the vocal­iza­tion cir­cuit, she said.

With tech­nol­o­gy devel­oped by Wang’s lab, they were able to locate and iso­late the spe­cif­ic neu­rons involved in the PAG’s cir­cuit­ry and then exper­i­ment on them.

By turn­ing the neu­rons on selec­tive­ly with a light-based method called opto­ge­net­ics, the researchers found they could make a mouse imme­di­ate­ly begin singing, even though it was alone.

On the oth­er hand, silenc­ing the activ­i­ty of the PAG neu­rons ren­dered court­ing male mice inca­pable of singing, even while they per­sist­ed in all of their oth­er courtship behav­iors.

The females turned out to be less inter­est­ed in the silent types, which also shows that the singing behav­ior is key to mouse sur­vival.

Both exper­i­ments firm­ly estab­lish that this “sta­ble and dis­tinct pop­u­la­tion of neu­rons” is the key con­duit between behav­ior and vocal com­mu­ni­ca­tion, Tschi­da said. The work will appear in the Aug. 7 edi­tion of Neu­ron, but was pub­lished ear­ly online in mid-June.

“These neu­rons are act­ing as a base for vocal­iza­tion. But they don’t deter­mine the indi­vid­ual parts of the song,” Tschi­da said. “It’s a ‘gate’ for vocal­iza­tion.”

Tschi­da, who will join the Cor­nell Uni­ver­si­ty fac­ul­ty next year, said the research will now trace PAG’s con­nec­tions to neu­rons down­stream that com­mu­ni­cate with the voice­box, lungs and mouth, for exam­ple. And they’ll work toward the behav­ioral cen­ters upstream that tell the mouse there is a female present and he should start singing.

The researchers hope to form a more com­plete pic­ture of why mice pro­duce dif­fer­ent syl­la­bles in dif­fer­ent con­texts. “We know they do it, but don’t know yet what parts of the brain dri­ve the behav­ior,” Tschi­da said.

This research was sup­port­ed by the Nation­al Insti­tutes of Health (MH103908, DC13826, MH117778).

Sto­ry Source:

Mate­ri­als pro­vid­ed by Duke Uni­ver­si­ty. Orig­i­nal writ­ten by Karl Leif Bates. Note: Con­tent may be edit­ed for style and length.

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