The study, "A Topographic Map of Recruitment in Spinal Cord," published in the March 1 issue of the journal Nature, maps how neurons in the bottom of the fish’s spinal cord become active during slow movements, while cells further up the spinal cord activate as movements speed up.
By removing specific neurons in the lower spinal cord with laser beams, the researchers rendered the fish incapable of slow movements. By removing nerves further up the backbone, the fish had difficulty moving fast.
"No one had any idea that organization like this existed in a spinal cord," said Joseph Fetcho, a Cornell professor of neurobiology and behavior and an author of the study. "Now that we know the pattern, we can begin to ask how that changes in disease states."
David McLean, Cornell postdoctoral researcher in Fetcho’s laboratory, was the first person to discover the pattern of neural activation and how it was associated with speed of movement. He is the lead author on the study.
The researchers worked with 4 millimeter-long larval zebrafish (Danio rerio) because they are transparent and researchers can see their cells. Fetcho and his colleagues injected the fishes?spinal cords with a fluorescent dye, which then lit up when calcium ions flooded in as the nerve cells activated. A confocal microscope with lasers allowed the researchers to image the cells at very high resolutions. Using this set up, they watched nerve cells light up as the animals moved at different speeds.
While no one knows how this pattern relates to other vertebrates, the research opens a door
Source:Cornell University News Service