Lion's Mane and NGF (nerve growth factor)

Nerve growth factor (NGF) is a protein that plays a significant role in the growth and protection of neurons. This is why one of the primary factors associated with neuro-degeneration is depleted levels of NGF, which decline with age especially in areas of the brain associated with memory. Age-dependent alterations in nerve growth factor (NGF)-related proteins, sortilin, and learning and memory in rats - PMC GDNF, NGF and BDNF as therapeutic options for neurodegeneration - PubMed

While NGF helps increase the production of new brain cells, it is also fascinating that it has the ability to down-regulate the inflammatory response.

Nerve Growth Factor Downregulates Inflammatory Response in Human Monocytes through TrkA | The Journal of Immunology | American Association of Immunologists

One of several therapeutic benefits of Lion's Mane Mushroom (hericium erinaceus) is that it's bioactive components (such as hericenones) are able to pass the blood-brain barrier and support the production of NGF.

Neurotrophic and Neuroprotective Effects of Hericium erinaceus - PMC Full article: Hericenones and erinacines: stimulators of nerve growth factor (NGF) biosynthesis in Hericium erinaceus