Learning takes some time, so Kao expected to wait for her results. But stimulating the LMAN had an immediate impact. The tune and rhythm of the basic song did not change, but a tiny burst of electricity would show up a few notes later as a change in volume or pitch at a particular time in the song.
The variations are usually too subtle for human ears, Kao said, but sensitive recording equipment can detect them. The systematic trials were possible with the aid of a computer program that could track the bird twitters and trigger stimulations to LMAN at precise moments to elicit measurable effects on a predetermined syllable, song after song.
The researchers found that different areas of LMAN tuned the same note in different directions, one area raising the pitch of a certain note and another area lowering its frequency. The moment-by-moment influence of this brain region on song is a new observation, Brainard said.
Next, the researchers analyzed the relationship between song and the natural neural activity of LMAN during the two types of male finch song, the performance-quality song directed at females, accompanied by some posturing and feather plumping, and the experimental solo variations, called "undirected," akin to singing in the shower. The brain region showed greater activity and more variable signaling during the undirected song, suggesting that this area is generating the variations of solo song.
Finally, they showed
Source:Howard Hughes Medical Institute
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