Mapped: how signals travel in a living organism

In a first, researchers have imaged all of the neurons firing in a living organism - revealing how signals travel through the body in real time.

Scientists mapped the connections among all 302 of a nematode worm's neurons.

By providing a means of displaying signalling activity between neurons in three dimensions and in real-time, the wiring diagram, or 'connectome', should allow scientists to predict what the nematode will do at any point in time.

"It should allow researchers to determine the neuronal pathways that lead to a particular action," said neuroscientist Alipasha Vaziri from University of Vienna.

Vaziri and his colleagues engineered C elegans worm so that when a neuron fires and calcium ions pass through its cell membranes, the neuron lights up.

To capture those signals, they imaged the whole worm using a technique called light-field deconvolution microscopy.

It combines images from a set of tiny lenses and analyses them using an algorithm to give a high-resolution 3D image.

The researchers took as many as 50 images per second of the entire worm, enabling them to watch the neurons firing in the brain, ventral cord and tail.

They were able to capture the activity of about 5,000 neurons simultaneously (the zebrafish has about 100,000 total neurons).

The next step is to use the technique to determine, and then to model, how neurons will respond to certain stimuli, said the study that appeared in the journal Nature Methods.