The Heterobasidiae edible mushrooms are a subclass of Basidomycetes, and the the fruiting bodies of Tremella fuciformis (TF), namely White-jelly-fungus or Silver-ear, are very popular in China as a medicinal remedy with nutritive and tonic actions for treating debility and exhaustion. A variety of semi-purified polysaccharides have been isolated and characterized from the TF spore (designated as polysaccharide A and B) 1) and the fruiting bodies. 2,3) Considerable attention has recently been drawn to the immunomodulating activities exhibited by their non-starch polysaccharide components, and especially the b-glucans.4) It has been found that the fermented solution and various extracts as well as the polysaccharide from TF 1,5,6) have several pharmacological activities, 7) such as enhancing the cellular and humoral immune functions, 6,8) and they also have anti-tumor, 9,10) hypoglycemic, 11,12) hypocholesterolemic, 13,14) anti-inflammatory, 1,3) antioxidant, 15) and anti-aging effects.16) The polysaccharide fraction has been clinically used in China for cancer patients who are being treated with chemotherapy or radiotherapy to enhance their immune function 8) and also for treating chronic hepatitis patients. 17) Previous to this study, we investigated that many kinds of medicinal herbs had a neuritogenic effect in PC12h cells. Among them, the aqueous extracts of Gardenia jasminoides, Panax ginseng, Epilobium macranthum and TF significantly enhanced nerve growth factor (NGF)-induced neuritogenesis (data not shown). Since the memory-associated increase in NGF in vivo is related with the central cholinergic neurons or synaptogenesis, which are both known to enhance the memory function, 18) it is possible that these bioactive herbal medicines may help improve memory.It has been reported that NGF and other neurotrophins play important roles in the growth, differentiation and survival of neuronal cells. 19,20) They are expected to have a regenerative action on the injured tissues in neurodegenerative diseases such as Alzheimer's disease (AD) and Parkinson's disease. However, because of their inability to cross the blood-brain barrier and their vulnerability to hydrolytic enzymes, they cannot be used as a medical treatment. AD is accompanied by pronounced neurodegenerative changes in the brain. The pathological features that have been identified in the central nervous system (CNS) of AD patients are senile plagues and neurofibrillary tangles, oxidative and inflammatory processes and neurotransmitter disturbances. A consistent neuropathological occurrence associated with memory loss is a cholinergic deficit, and this has been correlated with the severity of AD. [21][22][23][24] Cholinergic neurons in the CNS are believed to be involved in learning and memory of both human and animals. 25,26) The cholinergic approach to treating AD involves counteracting this loss in cholinergic activity by pharmacological intervention to increase the cholinergic transmission. 27) Animals and human studies have suggested that one of the m...