A breakthrough in nanotechnology has enabled doctors accurately to measure the levels of crucial chemicals in living brain cells in real time and at the level of a single cell.

Scientists at Stanford University and the Carnegie Institution's Department of Plant Biology claim to be the first successfully to apply genetic nanotechnology using molecular sensors to view changes in brain chemical levels.

The sensors alter their three-dimensional form on binding with the chemical, which is then visible via a process known as fluorescence resonance energy transfer, or Fret.

A newly published study from the scientists reveals how the nanosensors were introduced into nerve cells to measure the release of the neurotransmitter glutamate, the major brain chemical that increases nerve-cell activity in mammalian brains.

It is involved in everything from learning and memory to mood and perception. Too much glutamate is believed to contribute to conditions such as Alzheimer's and Parkinson's, the report stated.

"The fluorescent imaging technique allows us to see living cells do their jobs live and in colour," explained Sakiko Okumoto, lead author of the study at Carnegie.

"Fret is like two musical tuning forks which have the same tone. If you excite one, it gives a characteristic tone. If you bring the second fork close to the first one, it will also start to give you a tone even though they do not touch. This is resonance energy transfer."

Wolf Frommer, leader of the Fret team at Carnegie, added: "This is a tremendously exciting technology. I'm anxious to see what we can learn about the vast complexities of the brain over the coming years."