The mushroom itself seems to be beneficial, without need to resort to the synthetic ERG.
https://www.sciencedirect.com/topics/medicine-and-dentistry/ergothioneine
"Another commonly used mushroom in East Asian countries is Hericium erinaceus. It is an edible mushroom with medicinal value, which is also known as Lion’s Mane Mushroom or Hou Tou Gu in Chinese or Yamabushitake in Japanese. Polysaccharides extract of H. erinaceus has significant anticancer and immunomodulation activities. It enhanced T cells and macrophages secretion and enhanced the expression of cytokines [99]. In animal studies, H. erinaceus exerted hypolipidemic effects by reducing plasma total cholesterol, LDL, and triglyceride and hepatic HMG-CoA reductase activity [99].
Hericium erinaceus reports to have activities related to nerve and brain health. The polysaccharides of H. erinaceus can induce neuronal differentiation and promote neuronal survival. It has the ability to prevent the impairments of spatial short-term and visual recognition memory induced by β-amyloid peptide in animals [99]. Daily oral administration of H. erinaceus could promote nerve regeneration after injury in rats [100].
The neuroprotective effect on human was demonstrated. A double-blind, parallel-group, placebo-controlled trial was performed on 30 Japanese (age 50–80 years old) with mild cognitive impairment. The subjects took four Yamabushitake-containing tablets (each contained 96% of H. erinaceus) or placebo tablets three times a day for 16 weeks. The intervention group showed significantly increased scores on the cognitive function scale (Revised Hasegawa Dementia Scale (HDS-R)) compared with the placebo group (p<0.001). The scores decreased at week 4 after the termination. This study suggested the effectiveness of H. erinaceus in the prevention or the treatment of dementia and cognitive dysfunction [101]."