This site cites this specific source directly: PubMed, Hericium erinaceus and cognitive function research.
Worth noting this source uses the mushroom's scientific name, Hericium erinaceus, rather than the common name Lion's Mane — worth searching under both terms if you want the fullest picture of available research.
Like the Bacopa PubMed link, this is a search-results page surfacing multiple peer-reviewed studies — worth browsing directly rather than relying solely on this site's own summary of the research.