In a study published in Light: Science and Applications, noninvasive technology may now detect nerve cell firing based on shape changes. The method was developed by researchers at Stanford University, Palo Alto, California, and aims to observe neural activity in light-accessible regions of the body, such as the eye—making it possible for physicians to quantitatively monitor visual functions at a cellular level.
Image of a neuron in response to stimulation.
Credit: UCSD News
The study was funded by the NIH-National Eye Institute Audacious Goals Initiative for Regenerative Medicine. "Our task in this joint grant was establishment of the basic facts -- how fast and how much the cells move during action potential -- and to devise the best technical strategies for the system to be then used in humans," says Daniel Palanker, Ph.D. "I think this paper will be a solid reference regarding mechanical effects in cells when they fire."
The research will assist in the monitoring of the optic nerves in hopes to advance the understanding of optic nerve cell firing for better treatment strategies for ultimately restoring visual function in patients with retinal injury. "Non-invasive, all-optical, neural recording techniques like those being pioneered by Dr. Palanker and his team are very exciting because, unlike other methods, these can potentially be used in human eyes," explains the grant's principal investigator, Austin Roorda, Ph.D., University of California, Berkeley."These developments give promise for a day when we can study retinal diseases in human on a cellular scale and evaluate the treatments to cure them."
Everytime a nerve cell (neuron) fires, then there is a change in electrical potential (trans-membrane voltage). Present neural activity detection methods are invasive, which require the placement of an electrode near the nerves or certain markers that emit fluorescence to be placed inside the cell.
Watch this video below to learn more about changes that occur inside a neuron:
Now with the new technology developed by the Stanford team, it will be able to detect changes on cell structure from a side-effect of change in voltage. Specifically, nerve cells temporarily become round after it fires—these changes in shape can be detected by interferometric (phase) imaging as it senses variances in the alterations of light passing through the cell or reflected from its surface.
Signal from optical imaging (top) matches the signal from an electrode array (bottom).
Credit: Courtesy of Daniel Palanker, Ph.D., Stanford University.
"This nanometer-scale shape change is very difficult to see," said Palanker, "but with ultrafast quantitative phase imaging, it actually turns out to be visible."
Source: National Eye Institute