Researchers in the US and Austria have worked out a method of visualising neuron activity in real time, in 3D. This innovative approach is likely to lead to better understanding of brain disorders.
Modelling the nervous system in 3D to the millisecond; this is the ambitious project being carried out by researchers at the MIT Media Lab in the United States and the University of Vienna. This scientific breakthrough looks set to help scientists understand how the nervous system processes information and determines behaviour. Information transmitted by the neurons contains a multitude of data which command inter alia motricity and emotions. They use electrical impulses called ‘action potentials’, which provoke calcium ions to stream into each cell as it fires. By engineering fluorescent proteins to glow when they bind calcium, scientists can visualise this electrical firing of neurons.
Targeting neural activity with light
The experiment was carried out on worms of the C. elegans type, which is the only organism for which the entire neural wiring diagram is known and is therefore widely used in molecular biology studies. The 1-millimeter worm has 302 neurons, and was studied using a light-field microscope. This is the first time this method has been used to model brain activity and create 3D images. With the light-field microscope, the light emitted by the sample being imaged is sent through an array of lenses, which refract the light in different directions. Each point of the sample generates about 400 different points of light, which can then be recombined using a computer algorithm to recreate the 3D structure. Ed Boyden, a member of the MIT Media Lab faculty who is one of the leaders of the research team, explained that “if you have one light-emitting molecule in your sample, rather than just refocusing it into a single point on the camera the way regular microscopes do, these tiny lenses will project its light onto many points. From that, you can infer the three-dimensional position of where the molecule was.”
Towards more effective treatment of brain disorders
This is the first time scientists have used this approach to looking at the nervous system. The only comparable initiative is Big Brain, a freely accessible high-resolution 3D digital atlas of the human brain, which does not, however, look at neuron activity. “The ability to survey activity throughout a nervous system may help pinpoint the cells or networks that are involved with a brain disorder, leading to new ideas for therapies,” underlined Ed Boyden. The researchers also plan to combine this technique with optogenetics, which enables neuronal firing to be controlled by shining light on cells engineered to express light-sensitive proteins. By stimulating a neuron with light and observing the results elsewhere in the brain, scientists could determine which neurons are participating in particular tasks.