Neurons Work Like Dominoes

A team of MIT researchers have identified a 'chain reaction' in neurons, very similar to a cascade of falling dominoes, that controls the timing of the song of the zebra finch and which could be similar to human brain activity regulating the precise timing demanded by complex tasks.

The reason for which the team focused on the zebra finch, is because its song is stereotypical, each one lasting for about a second and containing many syllables, perfectly timed in every performance.

Michale Fee, senior author of the study, member of the McGovern Institute for Brain Research, and colleagues had shown in a previous research that the tempo of the song is controlled by a brain area called HVC – High Vocal Center.

This new study allowed them to see that during the very short song (1 second), the individual neurons in HVC had a short burst of activity at a very precise moment within the song.

As different neurons fire at different times, the researchers identified a pattern and concluded that the activity of these neurons sends instructions to the vocal organs at every moment of the song.

Once the perfect timing discovered, the scientists wandered where did it come from and after studying several theories, they opted for the “synfire chain” reaction, which is that of falling dominoes.

The team tested this theory by using intracellular recordings – recording small voltage differences within individual HVC neurons.

They used the latest technology to be able to do these recordings while the birds moved freely around its cage, because the goal was to record the natural behavior of singing.

The conclusion of the experiment was that the falling dominoes model does apply, as when individual neurons fire, they do it as if they were hit by the preceding neuron.

Fee said that “this is the first time we've been able to understand the generation of a learned behavioral sequence.

“We predict that similar mechanisms probably exist in other brains, including our own.”

The new study was published in the October 24 online issue of Nature.