Brain activity of worms recorded in 3D

Scientists have developed a new method to record 3D footage of neural activity in nearly the entire brain of a free-moving animal, an advance that could help better understand how neurons coordinate action and perception in animals.
The researchers from Princeton University in US used the technique to capture the first 3D recordings of neural activity in the nematode Caenorhabditis elegans, a worm species 1 millimetre long with a nervous system containing a mere 302 neurons.
They correlated the activity of 77 neurons from the animal's nervous system with specific behaviours, such as backward or forward motion and turning.
Previous work related to neuron activity either focuses on small subregions of the brain or is based on observations of organisms that are unconscious or somehow limited in mobility, said Andrew Leifer, from Princeton's Lewis-Sigler Institute for Integrative Genomics.

The system provides the most detailed picture yet of brain-wide neural activity with single-neuron resolution in an animal that is free to move around, Leifer said.
Neural networks are infinitesimal arrangements of chemical signals and electrical impulses that can include, as in humans, billions of cells.

The simple nervous system of C elegans provided with a more manageable testing ground for their instrument.
It also could show information about how neurons work together that applies to more complex organisms, Leifer said.
For instance, the researchers were surprised by the number of neurons involved in the seemingly simple act of turning around.

"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," Leifer said.
"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," he said.
The researchers designed an instrument that captures calcium levels in brain cells as they communicate with one another.
The level of calcium in each brain cell tells the researchers how active that cell is in its communication with other cells in the nervous system.

The researchers induced the nematodes' brain cells to generate a protein known as a calcium indicator that becomes fluorescent when it comes in contact with calcium.
They used a special type of microscope to record in 3D both the nematodes' free movements and neuron-level calcium activity for more than four minutes.
The study was published in the journal PNAS.