Both monoamine oxidases A and B have been involved in the altered aminergic neurotransmitter levels seen in AD.53 Activated MAO-A/B can destroy cholinergic neurons, induce amyloid β peptide production and accumulation, formation of neurofibrillary tangles and subsequent cognitive dysfunction.54 Selegiline, an MAO inhibitor used to treat Parkinson’s disease, has been tested for the treatment of memory impairment in AD. The gene discussed is MAOA; the disease is memory impairment.