Stanford scientists have demonstrated a technique for observing hundreds of neurons firing in the brain of a live mouse, in real time, and have linked that activity to long-term information storage. The unprecedented work could provide a useful tool for studying new therapies for neurodegenerative diseases such as Alzheimer’s.
The researchers first used a gene therapy approach to cause the mouse’s neurons to express a green fluorescent protein that was engineered to be sensitive to the presence of calcium ions. When a neuron fires, the cell naturally floods with calcium ions. Calcium stimulates the protein, causing the entire cell to fluoresce bright green.
A tiny microscope implanted just above the mouse’s hippocampus — a part of the brain that is critical for spatial and episodic memory — captures the light of roughly 700 neurons. The microscope is connected to a camera chip, which sends a digital version of the image to a computer screen.
The computer then displays near real-time video of the mouse’s brain activity as a mouse runs around a small enclosure, which the researchers call an arena.
The neuronal firings look like tiny green fireworks, randomly bursting against a black background, but the scientists have deciphered clear patterns in the chaos.