Thanks for your comment.
There is a lot of research regarding brain regeneration.
Please feel free to look at this link here, and all the other's evident in the post.
In regards to fasting times, there is no better way to discover the benefits of fasting by trying it out for yourself. Most people decide to fast because of the fat loss benefits, but are highly surprised as to how many other benefits come about from skipping a meal.
If you would like to reference any information from a doctors perspective, Dr Jason Fung leads the way with his research and discoveries on this one. I do believe he's on Medium. But, you can read any of his books.
Another good one is Dr Gundry, although he focuses on gut health a lot more and the immune system.
I do hope this helps you, but just to give you my own findings, I fast for 17-20 hours per day, give or take according to my own lifestyle needs. : )
Have a great day.