In a scientific first that could help us better understand how
signals travel in the brain, a researcher of natural sciences at
Harvard has created neurons that light up as they fire.
Despite the fact that almost every science
animation ever created has shown neurons to light up, in
reality there is no obvious visual cue to indicate their electrical
activity. The genetically-altered neurons use a gene from a
Dead Sea microorganism that produces a protein that fluoresces when
exposed to the electrical signal in a neuron, allowing researchers
to visually trace how signals are transmitted through
The research was lead by Adam Cohen, Associate Professor of
Natural Sciences, and was published in Nature Methods.
Cohen said of the research: "It's very exciting. In terms of
basic biology, there are a number of things we can now do which
we've never been able to do. We can see how these signals spread
through the neuronal network. We can study the speed at which the
signal spreads, and if it changes as the cells undergo changes. We
may someday even be able to study how these signals move in living
In order to create the snazzy neurons, the team cultured brain
cells in the lab and then infected them with a genetically-altered
virus that contained the protein-producing gene. Once the cells
were infected, they started to manufacture the protein themselves,
which allowed them to light up.
A neuron has an active membrane around the whole cell and
normally the inside of the cell is negatively-charged relative to
the outside. However, when the neuron fires, the voltage reverses
briefly (for around 1/1,000th of a second). This brief spike
in voltage travels down the neuron and then activates other neurons downstream. The genetically-altered protein sits in the
membrane of the neurons and light up as the pulse passes through
The research could aid our understanding of how electrical
signals move through the brain and around the body, Cohen
He explained: "Before, the best way to make a measurement of the
electrical activity in a cell was to stick a little electrode into
it and record the results on a volt meter. The issue, however, was
that you were only measuring the voltage at one point, you weren't
seeing a spatial map of how signals propagate. Now, we will be able
to study how the signal spreads, whether it moves through all
neurons at the same speed, and even how signals change if the cells
are undergoing something akin to learning."
Using electrodes can also kill the cells relatively quickly, so
it's hard to perform longer studies. The new technique could allow
researchers to study cells for much longer.
The research could also prove useful for the development of
drugs, many of which target ion channels --
proteins that play an important role in governing the activity of
the heart and brain. Currently, if researchers want to test a
compound designed to activate or deactivate an ion channel, they
have to test it with an electrode, then add the drug and see what
happens - a process that takes a few hours for every data
point. The ability to see how neurons are firing could
radically speed up the testing process.
You can read the full study, titled Optical recording of action potentials in mammalian neurons using a
microbial rhodopsin here.