Meanwhile, Parnetti et al. (2014) found that PDD patients have significantly higher CSF t-tau levels than that of PD patients without cognitive impairment (Andersson et al., 2011), and the PD patients who have higher concentrations of CSF t-tau and p-tau are more likely to suffer from impairment of memory and visuospatial dysfunction. This evidence concerns the gene MAPT and Cognitive impairment.