How do our eyes work? How do they transform the scenes around us into neural signals that our brains interpret and act upon? Neuroscientists like Joshua Sanes, Professor of Molecular and Cellular Biology and Director of the Center for Brain Science at Harvard, study the retina because they believe it may be the first part of the mammalian brain for which we can fully address the mysteries of how neural circuits develop and process information.

Over the years, studies of retinal neurons have yielded many answers, from new insights on how synapses assemble and how neuronal subtypes are specified to how we detect motion or how our brains encode maps of physical space. However, neuroscientists wishing to track the firing patterns of individual neurons in the retina have not been able to record in vivo in awake, behaving animals the way they can for many other parts of the brain. Until recently, they’ve had to dissect out the retina, separating it from the rest of the body, in order to carry out their recordings.

But a groundbreaking new technology from the lab of Charles Lieber, Professor and Chair of the Department of Chemistry and Chemical Biology at Harvard has changed all this. Lieber’s team, led by postdoctoral fellow Guosong Hong and former graduate student Tian-Ming Fu, has developed tiny, ultraflexible mesh electronics that can be injected into the mouse retina. These electronics integrate into the tissue without causing damage—allowing for non-invasive long-term recordings of neural activity, gathered simultaneously from a number of individual retinal ganglion cells.

Working with Sanes and Mu Qiao, a former graduate student in his lab, they’ve already demonstrated the biological value of this incredible new tool for retinal research. Tracking retinal ganglion cells in healthy mice going about their business for a period of two weeks, the researchers explored circadian rhythms in the firing patterns of these cells—learning things which they simply could not be if they were working with the retina ex vivo.

“Now we can do things that were a dream before,” Lieber said in a news story for the Chemistry and Chemical Biology website. “Since the 1970s, the only way to measure this fundamental sensory input has been with invasive, surgical procedures to remove the eye from the animal, (so) I think this opens up completely new opportunities for vision research.”

“This was a very satisfying set of results,” said Sanes. “We were able to confirm some things we suspected, learn some new things, and set the stage for finding out what happens during the early phases of diseases like macular degeneration and glaucoma. Diagnosis of these blinding diseases often comes too late for effective treatment.  Maybe the new technology will help us find a way to change that.”

To learn more:
“Revolutionizing retinal studies”, a story on the Chemistry and Chemical Biology website
“A method for single-neuron chronic recording from the retina in awake mice”, the original journal article in Science

Thumbnail image and video link above provided by Lieber lab at Harvard.