MAPT and Alzheimer disease: A number of underlying pathophysiologies account for the cognitive impairment of PD; (i) abnormal reduction of neurotransmitters (dopamine, acetylcholine, noradrenaline, serotonin); (ii) the presence of cortical Lewy bodies; (iii) concomitant Alzheimer’s disease (AD) pathology (i.e. hippocampal atrophy and abnormal disposition of beta amyloid and phosphorylated tau); (iv) concomitant vascular pathology; and (v) pharmaceutical interaction in cognition.