Brain's chemical signals seen in real time

Scientists have developed a new technique that allows them to see what happens in the brains of live animals in real time, an advance that may eventually lead to a greater understanding of how we learn, develop and fight addictions.
"We developed cell-based detectors called CNiFERs that can be implanted in a mouse brain and sense the release of specific neurotransmitters in real time," said Paul A Slesinger, of the Icahn School of Medicine at Mount Sinai in the US.
Scientists used the technique to what happens in the brains of mice while revisiting a famous experiment that was conducted by Russian physiologist Ivan Pavlov more than a hundred years ago, in which he conditioned dogs to salivate at the ringing of a bell.

Neurotransmitters are the chemicals that transmit messages from one neuron to another. CNiFERs stands for "cell-based neurotransmitter fluorescent engineered reporters."
These detectors emit light that is readable with a two-photon microscope and are the first optical biosensors to distinguish between the nearly identical neurotransmitters dopamine and norepinephrine.
These signalling molecules are associated respectively with pleasure and alertness.

Researchers conditioned mice by playing a tone and then, after a short delay, rewarding them with sugar. After several days, the researchers could play the tone, and the mice would start licking in anticipation of the sugar.
"We were able to measure the timing of dopamine surges during the learning process," Slesinger said.

"That's when we could see the dopamine signal was measured initially right after the reward. Then after days of training, we started to detect dopamine after the tone but before the reward was presented," he said.
Researchers also studied the first biosensors that can detect a subset of neurotransmitters called neuropeptides.
Ultimately, Slesinger said they would like to use this sensing technique to directly measure these neuromodulators, which affect the rate of neuron firing, in real time.