Through a mouse’s eye
An injectable mesh can register the nerve impulses inside the eye of a living mouse.
Scientists have developed an injectable mesh that covers the retina of lab animals, recording the neural activity of their eyes in vivo. Initial results suggest that the mesh is safe and effective, even for providing data on the circadian rhythm of cells that process light information in the retina.
Most studies of the eye require sacrificing lab animals and analyzing their eyes post-mortem, which provides limited insights into the plasticity of cells in the eye. To date, only a few studies of the neural activity in the retinas of live, large animals have been done.
Here, Guosong Hong and colleagues at Harvard created miniature, flexible mesh devices that can be injected into the retinas of mice to monitor neural activity. Through a series of tests, they confirmed that the mesh devices conform to the retinal surface and remain localized. The devices do not impair eye movement or the processing of light.
Next, the researchers analyzed how well the devices monitor the activity of retinal ganglion cells (RGCs), which process visual information relayed by photoreceptors. They were not only able to monitor individual RGCs repeatedly over a two-week period, but they could also identify those responsible for discerning the orientation and direction of visual cues. Lastly, the researchers monitored RGCs at 4-hour intervals over several day/night cycles; the data reveal that RGCs fire on average 77% higher than during the day-time circadian phase than during the night-time phase.