Fasting upregulates BDNF in the brain regions that are responsible for memory and learning.
Autophagy helps clearing junk from cells / promotes apoptosis of defective cells which improves overall functioning and reduces inflammation (inflammation is linked with a bunch of neurogenerative disease).
Ketosis adaptation allows the brain to function well with ketone bodies which reduces reliance on blood glucose (and prevents glucose crashes).
Prolonged fasting has been linked with production and release of DMT via the pineal gland which can have positive impacts on depression, anxiety and open mindedness.
Psychiatrist Dr. Tracy Marks talks about the antidepressant effects of IF and how it stimulates neural growth
Another book by neuroscientist kristen willeumier talks about cognitive effects of IF in her book Biohacking the Brain
And theres always google scholar and ncbi if you wanna dive directly into the scientific literature. Main thing there is learning how to read a scientific article, esp. when you dont know all the terminology and concepts. Doing so is a great learning experience though to try and process one or two articles. Just read the abstract and maybe part of the intro and results sections
Edit I think Dr. Valter Longo mentioned in his book The Longevity Diet about how prolonged fasting (e.g. 5 days) can induce stem cells in the brain. These are basically building blocks for new neurons and we lose stem cells later in life