The increase in the elderly population is greatly increasing the number of patients suffering from macular degeneration. It is also called “elderly macular degeneration” in relation to age. “The macula” is the most important part of the eye’s retina, which acts as a film when it comes to photography. It is macular degeneration that causes vision impairment due to various pathological changes (deformation) in this area as you get older. Some cases lead to blindness depending on the progress. It is an important and frightening disease that takes the top cause of the elderly’s blindness.
In these macular degenerative diseases, artificial retinal devices that electrically stimulate surviving retinal nerve cells are the only way to recover vision. However, there is a problem that artificial retinal devices have significantly lower vision compared to normal vision.
Dr. Im Mae-soon’s team at the Korea Institute of Science and Technology (KIST) confirmed that high signal diversity in different optic cells is a key factor for high-efficiency visual information delivery. This theory is expected to contribute greatly to the field of artificial vision.
KIST researchers quantified visual information transfer by applying computational neuroscience and information theory to neural signals obtained from rabbit retinal nerve cells.
In particular, the research team, which noted diversity among several features of neural signals, confirmed that the higher the diversity of information patterns between different cells, the greater the amount of information.
The research team compared the visual information transfer method of normal retinal and artificial retinal devices through electrical stimulation experiments. As a result, the research team confirmed that cells involved in responses that artificial retinal users perceive more easily show higher neural signal diversity. On the other hand, cells responsible for responses that users were not aware of lost the diversity of intercellular signals seen in normal light stimuli and produced highly uniform neural signals for electrical stimuli.
This loss of neural signal diversity has led to a severe reduction in visual information transmitted. Lack of information makes it difficult for the brain of artificial retinal device users to interpret.
Dr. Lim Mae-soon previously studied mice with advanced retinal degeneration and confirmed that the consistency of signals delivered by each optic cell is an important factor in stable visual recognition.
“It means that it is difficult to successfully implement very complex visual information just by stimulating nerve cells,” said Dr. Kang Joon-ho of KIST. “If different cells create different neural signals, high-quality artificial visualization will be possible.”
“Taken together with last year’s study, it seems that different optic cells must consistently transmit various neural signals to recognize vivid visual information in our heads,” Dr. Lim Mae-soon said. “This study shows that we need to try to simulate signal diversity in complex neural networks, not just in artificial vision.”
Reference: J. H. Kang, Y. J. Jang, T. Kim, B. C. Lee, S. H. Lee and M. Im, “Electric Stimulation Elicits Heterogeneous Responses in ON but not OFF Retinal Ganglion Cells to Transmit Rich Neural Information,” in IEEE Transactions on Neural Systems and Rehabilitation Engineering, doi: 10.1109/TNSRE.2020.3048973.