Science Discovery: A special function in the eye that explains why the day doesn't know the darkness of the night...

For decades, biology textbooks have taught us that the eye and the brain communicate through only one signaling pathway - what you see is what you get.but we all know that entering a small dark room in the daytime doesn't mean it's time to go to bed.why? In a new study published in science on May 1, Beijing time, a team from Northwestern University in the United States found that some retinal neurons chose a "rarely traveled path.".this result explains why our sensitivity to ambient lighting conditions is much lower than that of conscious visual perception.retinal ganglion cells (RGCs) transmit light signals from the retina to the brain, which were previously thought to signal only by releasing excitatory neurotransmitters.in short, excitatory signals make neurons discharge more; inhibitory signals make neurons discharge less.this new study shows that a subgroup of retinal ganglion cells (iprgc) sends inhibitory signals to the brain to drive a variety of photoinduced behaviors, including non imaging behaviors.in the sections of mouse retina, the nuclear markers were blue, the inhibitory cells were purple, and the iprgc was green.Image Source: Northwestern University researchers found that these retinal neurons are involved in subconscious behavior, such as synchronization of circadian rhythm and light intensity cycle, and synchronization of pupil contraction and strong light.by better understanding the function of these neurons, researchers can explore new ways in which light affects our behavior.co author of the study and assistant professor of Neurobiology at Northwestern University, Tiffany Schmidt, said: "these inhibitory signals prevent our circadian clock from readjusting in dim light and prevent the pupil from contracting in weak light.both signals can adapt to normal visual and daily functions.we believe that the results of this study provide a mechanism to understand why our eyes are so sensitive to light intensity while our subconscious behaviors are not."in this new study, Schmidt and her team blocked retinal neurons that inhibit signal transduction in a mouse model.when this signal is blocked, dim light can more effectively change the circadian rhythm of mice.Schmidt said: "this shows that when the ambient light changes unexpectedly, the eye sends a signal to actively inhibit the readjustment of circadian rhythm, which is unexpected.however, it makes sense, because we don't adjust the whole body's circadian clock for the tiny interference of the bright or dark cycle of the environment. Br / > will only be adjusted in the case of large-scale light . "Schmidt's team also found that mice's pupils were more sensitive to light when inhibitory signals from the eye were blocked. Takuma Sonoda, the lead author of the study and a doctoral student in interdisciplinary neuroscience at Northwestern University, said: "our working hypothesis is that this mechanism prevents the pupil from contracting in very low light. this increases the intensity of light shining on the retina, making it easier to see things in low light conditions. this mechanism at least partly explains why our pupils don't contract before light intensifies. "reference: a non-governmental investment circuit transformers behavioral sensitivity to lightdoi: 10.1126/ science.aay3152