This site names Lion's Mane specifically and ties it to nerve growth factor research — worth a standalone look at that specific claim.
This site describes it directly: a culinary and medicinal mushroom studied for nerve growth factor and for memory in small human trials of older adults — worth noting "small" is this site's own qualifier, not an omission.
This site is direct: results are promising but based on limited research — worth reading that qualifier as this site setting realistic expectations rather than overstating the evidence behind this named ingredient.