NGF and Alzheimer disease: In view of the notion that, the synaptic density correlates more closely with memory/learning impairment than any other pathological lesion observable in the AD neuropathology [101] and that dysfunction of NGF/TkA signaling underlies the selective degeneration of cortical cholinergic projecting neurons in AD pathogenesis [29], septal primary cultures have been recently employed by our research group with the intent of analyzing the NGF activity and consequences, at the synaptic level, of its in vitro withdrawal.