Here is a recent review of over the counter supplements for memory; I was happy to see a favorable view of curcumin and lion's mane:

Over the Counter Supplements for Memory: A Review of Available Evidence - PubMed (nih.gov)

​

In lion's mane supplements, it is Erinace A, which supports nerve growth factor (NGF), that is found in the mycelium:

Lion’s Mane Mushroom Benefits* (hostdefense.com)
While both mushroom fruiting body and mycelium are beneficial, the mycelium appears to be more more important in lion's mane, chaga, agarikus, and cordyceps militaris.
Fruiting Body versus Mycelium: a misguided debate  • Sempera Organics

​

Multi-vitamin supplements have been found to be beneficial:

Multivitamin Supplementation Improves Memory in Older Adults: A Randomized Clinical Trial - PubMed (nih.gov)

​

Among curcumin supplements, one specific form has a published Alzheimer's study, and previous research done at UCLA with predementia:

Theracurmin Supplementation May be a Therapeutic Option for Older Patients with Alzheimer's Disease: A 6-Month Retrospective Follow-Up Study - PubMed (nih.gov)