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Hankyung Choi Professor, Department of Brain Science, Daegu Gyeongbuk Institute of Science and Technology |
Light affects us more than we can see objects or text. To understand this process, we need to think about the eye for a moment.
Humans perceive light with their eyes. The ‘cone cells’ and ‘rod cells’ we learned from textbooks occupy the majority of retinal cells and form images by sensing light, darkness, or color.
There are also ‘photosensitive ganglion cells’ that are different from these. These cells only sense the light and darkness around them. Cone and rod cells contribute to vision formation along a relatively limited path, but photosensitive ganglion cells are involved in functions other than vision by forming a neural circuit directly to various areas of the brain. For example, the biological clock is used to adapt to jet lag and to change mood according to the surrounding brightness.
Research on the function of photosensitive ganglion cells has been almost conducted in adults, ie, adults, and it is not well known how they affect the development of children. Unlike other cells in the retina, photosensitive ganglion cells have the potential to have a greater impact on the development process because they fully function right after birth. Tian Shu, a professor at the China University of Science and Technology, and colleagues studied the problem using mutant mice.
Cone and rod cells sense light through a protein called ‘rhodopsin’. On the other hand, photosensitive ganglion cells sense light through a protein called melanopsin. Noting that the genes involved in these proteins are different, Professor Shu and his team studied mice in which only melanopsin was removed. These mice have normal visual function, but cannot detect brightness through photosensitive ganglion cells.
The research team examined the auditory cortex, somatosensory cortex, and prefrontal cortex, which are independent of light, in the brains of mice that had been deprived of melanopsin by birth. Then, the number of synapses was reduced, and the neural activity was also low. These results can be interpreted as the light-sensing function of melanopsin has an important effect on synapse formation.
Synapses are places of communication between neurons, and they play a particularly important role in learning and memory. If so, does the difference in synaptic structure or activity seen depending on the activation of photosensitive ganglion cells in the early stages of life affect the learning ability of adults? There is a need to investigate the possibility that damage to photosensitive ganglion cells may lower the brain’s ability to study.
The researchers tested the learning ability of adult mice through simple behavioral experiments. It was to see if mice could learn the simple rule that food would come out when they heard a high sound and no food was given when they heard a low sound. This action does not require any use of ambient light sensing capabilities.
However, the mutant mice, which lost melanopsin by birth, did not perform this behavior properly. On the other hand, melanopsin was normal in childhood, but learning ability was normal in the special mutant mice, which lost their function after becoming adults. The learning ability of animals required the normal function of photosensitive ganglion cells during the growth period.
The study did not specifically address which lights are suitable for brain development and which ones are bad. Accordingly, it is too early to make specific suggestions for lighting in children’s rooms. However, considering that research on photosensitive ganglion cells is giving inspiration for designing building lighting or electronic device screens in a healthier direction, there is a lot of thought about what kind of lighting to provide for children as well as adults in the future. it seems necessary
Hankyung Choi Professor, Department of Brain Science, Daegu Gyeongbuk Institute of Science and Technology
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