What goes on in the brain of a worm?

After capturing 3D footage of neural activity in an area covering nearly the entire brains of these tiny worms, researchers at Princeton University now know.

And, they say the information could help further understanding of neuron activity in all brains, including humans'.

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Researchers studied the nematode Caenorhabditis elegans, a species that is just 1 millimetre long and has a nervous system containing 302 neurons. With the images, the team was able to trace specific behaviours, like backward or forward motion, to the activity of 77 neurons in the nervous system

HOW THEY DID IT Researchers studied the nematode Caenorhabditis elegans, a species that is just 1 millimetre long and has a nervous system containing 302 neurons. With the images, the team was able to trace specific behaviours, like backward or forward motion, to the activity of 77 neurons in the nervous system. To capture the footage, researchers designed an instrument that records calcium levels in the brain as they communicate, and tracked the activity. Using a calcium indicator, a protein that the researchers induced in the cells, the researchers were able to see when cells came in contact with calcium by a fluorescent glow. Then, they used a special microscope to capture the 3-D footage of free movements and neuron level calcium activity for more than four minutes. Advertisement

The recordings taken by Princeton scientists are the first to examine nearly the entire brain of a free-moving animal.

Researchers studied the nematode Caenorhabditis elegans, a species that is just 1 millimetre long and has a nervous system containing 302 neurons.

With the images, the team was able to trace specific behaviours, like backward or forward motion, to the activity of 77 neurons in the nervous system.

Earlier research has only focused on small subregions of the brain, or observation of an unconscious or limited-mobility organism, according to Princeton.

'This system is exciting because it provides the most detailed picture yet of brain-wide neural activity with single-neuron resolution in the brain of an animal that is free to move around,' said Andrew Leifer.

Leifer is an associate research scholar in Princeton's Lewis-Sigler Institute for Integrative Genomics, and corresponding author of the paper.

'Neuroscience is at the beginning of a transition towards larger-scale recordings of neural activity and towards studying animals under natural conditions,' he said.

'This work helps push the field forward on both fronts.'

In the human nervous system, billions of cells make up the networks which dictate chemical signals and electrical impulses.

With its simpler nervous system, C. elegans allowed researchers to test new recording methods, while sill revealing information about the behaviours of neurons that could be applied on a larger scale.

To capture the footage, researchers designed an instrument that records calcium levels in the brain as they communicate, and tracked the activity.

The upper left panel shows the position of the nuclei in all the neurons in an animal's brain, while the upper right panel recorded neural activity indicated by a fluorescent dye. The lower left shows the animal's posture on the microscope plate. At bottom right is a low-magnification fluorescent image of a nematode brain

Using a calcium indicator, a protein that the researchers induced in the cells, they were able to see when cells came in contact with calcium by a fluorescent glow.

Then, they used a special microscope to capture the 3D footage of free movements and neuron level calcium activity for more than four minutes.

'One reason we were successful was that we chose to work with a very simple organism,' Leifer said.

'It would be immensely more difficult to perform whole-brain recordings in humans. The technology needed to perform similar recordings in humans is many years away.

'By studying how the brain works in a simple animal like the worm, however, we hope to gain insights into how collections of neurons work that are universal for all brains, even humans.'

Now, the researchers are working to understand how neural activity and behaviour correlate. In their next steps, Leifer says they will use mathematical and computer models to test how neural activity changes behaviour.