Hericium erinaceus

Hericium erinaceus (also called Lion’s Mane Mushroom, Bearded Tooth Mushroom, Satyr’s Beard, Bearded Hedgehog Mushroom, pom pom mushroom, or Bearded Tooth Fungus) is an edible and medicinal mushroom belonging to the tooth fungus group. Native to North America, Europe and Asia it can be identified by its long spines (greater than 1 cm length), its appearance on hardwoods and its tendency to grow a single clump of dangling spines.^[1] Hericium erinaceus can be mistaken for other species of Hericium, all popular edibles, which grow across the same range. In the wild, these mushrooms are common during late summer and fall on hardwoods, particularly American Beech. 

Considering the increase of degenerative conditions, scientists around the world have launched investigations on this mushroom possible anti-dementia compounds^{[citation needed]}.

Primary research has demonstrated the following:

• Stimulated animal nerve cells.^[7]
• A double-blind, parallel-group, placebo-controlled trial showed improved cognitive ability in individuals with mild cognitive impairment.^[8]
• Stimulated nerve growth factor in an in vitro experiment with human astrocytoma cells.^[2] Nerve growth factor stimulated by phenol-analogous Hericenone.^[9]
• Stimulated myelination in an in vitro experiment.^[10]
• Regenerated peripheral nerves following crush injury^[11]

Long-term safety and effects of withdrawal seem to be unknown.

(From Wikipedia on 13.9.15)

References:

Catalogue of Life  Wikipedia 
Mushroom Expert  mykoweb  nrcmushroom  Two new records of hydnoid fungi from the Western Ghats of India Article