What’s that mouse thinking about? Scientists at California’s Stanford University can now tell you – to a limited extent. They recently had success in imaging the neural activity of mice, in real time. While the ability to “read a mouse’s mind” may not fire many peoples’ imaginations, the technology could prove very useful in researching diseases like Alzheimer's.
The researchers started by using gene therapy to cause the animals’ neurons to express a fluorescent green protein. That protein was engineered to react to the presence of calcium ions, which neurons flood with when they fire. This means that when one of the neurons was active, it would fluoresce green.
In order to see those fluorescing neurons, the scientists then implanted a tiny microscope above each mouse’s hippocampus, where it could image roughly 700 of the nerve cells. The hippocampus was chosen due to its role in spatial memory, which was part of the focus of the study.
The microscope was wired to a camera chip, which in turn transmitted a real-time image of the neurons to a computer screen. When the mice were subsequently released into an enclosure known as the arena, it was observed that the same combinations of neurons would fluoresce each time they returned to a given area. It got to the point where the scientists could tell where in the arena a mouse was, simply by looking at which of its neurons were firing. These patterns remained the same for each area, even after several months.
“The hippocampus is very sensitive to where the animal is in its environment, and different cells respond to different parts of the arena,” said associate professor of biology and of applied physics, Mark Schnitzer. “Imagine walking around your office. Some of the neurons in your hippocampus light up when you're near your desk, and others fire when you're near your chair. This is how your brain makes a representative map of a space.”
It is now hoped that such fluorescing mice could be used to develop treatments for neurodegenerative diseases. If specific neurons were observed to have stopped functioning in one of the mice, for example, the scientists could use the technology to see if a certain medication was able to restore their function when exposed to the same stimuli.
A paper on the research was recently published in the journal Nature Neuroscience. One of the mice – and its neurons – can be seen in action in the video below.
Source: Stanford University