Summary: Researchers have identified a new type of retinal ganglion cell.
source: Northwestern University
Northwestern Medicine researchers have identified a new type of retinal ganglion cell, the retinal neurons that encode the visual environment and transmit information back to the brain, according to a study published in neuron.
A specific feature of this cell, called a “flow suppressed in contrast” (bSbC) retinal ganglion cell (RGC), overturns a decades-old assumption about the relationship between cell input from photoreceptors and output to the brain, according to Gregory Schwartz, PhD, professor of ophthalmology by Derek T. . Phil is the study’s senior author.
“The classic view was that these ganglion cells simply integrate excitatory and inhibitory inputs, and that will tell you how the cell responds to visual stimuli,” said Schwartz, who is also a professor of neuroscience.
“Our findings reveal that these cells have their own self-accounts, which have interesting implications for things like retinal prosthetics.”
There are more than 40 types of RGCs that convey information about specific and complex characteristics of a visual scene, including movement, direction, orientation, and color. For example, the ‘OffsA’ type RGC has a base rate of firing, but when the light increases, the cell signal to the brain decreases and vice versa.
In the study, the researchers compared the responses of the ganglion cell types OFFsA and bSbC to different visual stimuli, recording the resulting signals that would be sent to the brain. The study authors discovered that bSbC has a peculiar mechanism: the cell has a base rate of signaling toward the brain, but both increases and decreases in light lead to decreased signaling, a one-way signaling pattern.
“The signal can only go down,” Schwartz said.
Furthermore, the researchers tested the classic view of how ganglion cells integrate with input. These cells receive excitatory and inhibitory signals from photoreceptors in the retina, and the prevailing theory dictates that these inputs combine to reach a certain threshold causing a change in signal output.
To test this, Schwartz and his collaborators swapped the inputs into OFFsA and bSbC ganglion cells with each other, and found that the output signal in this experiment was identical to normal activity.
“This means that they have their own ion channels that influence the output, and their own set of electrical conductors that contribute to the output,” Schwartz said.
The findings have implications for devices such as retinal prosthetics, which are intended to stimulate adjacent stem cells that no longer respond to light. Current prosthetics can only produce blunt vision, and Schwartz believes part of the problem is that prosthetics send the wrong signals to the wrong types of cells.
“You can’t turn on the light to check the type of retinal ganglion cells because the receptors are damaged — it’s a problem 22,” Schwartz said.
Alternatively, investigating the intrinsic computations in each cell type can help scientists determine which cells, even without the correct photoreceptor insertion.
“If you can get detailed information about these onboard calculations, you might be able to send the right signals for each cell type,” Schwartz said.
About this research in visual neuroscience news
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“Differences in spike generation rather than synaptic input selectively determine the advantage of the two types of retinal cellsWritten by Sophia Weinbar et al. neuron
Differences in spike generation rather than synaptic input selectively determine the advantage of the two types of retinal cells
- Distinguishes the type of contrast-suppressed retinal ganglion cell in the mouse
- It goes into a depolarizing block in response to negative contrast stimuli
- Depolarizing mass of low sodiumFifth Conductivity, AIS is shorter, and less than NaFifth1.6
Retinal ganglion cells (RGCs) are the spinous projective neurons of the eye that encode various features of the visual environment.
Circuits providing synaptic inputs to different types of RGC to drive feature selectivity have been studied extensively, but there has been little research aimed at understanding intrinsic properties and how they affect feature selectivity.
We present the type of RGC in the mouse, a Bursty Suppressed-by-Contrast (bSbC) RGC, and compare it to OFF continuous alpha (OFFsA).
The differences in their contrast response functions arose from differences not in synaptic inputs but in their intrinsic properties. Spike’s generation was the main intrinsic characteristic behind this functional difference; bSbC RGC undergoes mass depolarization while OFFsA RGC maintains a high spike rate.
Our results demonstrate that differences in intrinsic properties allow these two types of RGC to detect and relay hallmarks of a similar visual stimulus to the brain.