Microscopic imaging techniques have enabled scientists to delve deep into the brain of a living animal to see how visual circuitry works.
By combining two imaging methods, researchers at Harvard Medical School in Massachusetts produced time-lapse images that gave them a close-up look at the inner workings of the brain — an achievement that could improve understanding of complex illnesses such as epilepsy, Alzheimer’s and Parkinson’s disease.
“Put simply, this technique allows us to see the brain seeing,” R. Clay Reid, professor of neurobiology and the lead researcher, said Wednesday. “It’s an entirely new way of looking at brain function.”
Watching how the brain works
Reid and his team tracked for the first time the responses of neurons in the brains of rats simultaneously as they produced vision in the animals.
The scientists, who described the research in the latest edition of the journal Nature, believe the method could also be used to analyze how the brain works during other activities such as movement, learning and thinking.
“Never before have we been able to look into a brain at 100 neurons and say, ‘I know what every single one of those neurons is doing,”’ Reid said.
Neurons filled with dye
To produce the images of the brain at work, Reid and his colleagues filled neurons in an area of the brain called the visual cortex with a special dye that shines when calcium in the cell rises, which is an indication that nerve cells are firing.
The visual cortex processes neuronal input from the eye into the images we see.
The cells were then illuminated with a high-powered laser, and a sophisticated microscope was used to take the time-lapse pictures of the neurons as the animals were shown an image. The brain activity is shown on a computer screen.
What they saw was completely unexpected.
They were surprised by the degree of precision in the part of the visual cortex that is sensitive for motion. In that region, the neurons were very highly segregated, according to Reid.
“We have rodent models of Alzheimer’s disease, Huntington’s disease and Parkinson’s disease, and this imaging will be a powerful tool to dissect the cellular basis for the cognitive problems we see in these diseases,” Bradley Hyman, a researcher at Massachusetts General Hospital, who was not part of the research team, said in a statement.
