MAPT and Parkinson disease: The PD brains also had significantly increased insoluble levels of 0N3R and 1N4R tau isoforms compared to controls in ctx-fg (0N3R tau: 4.2 ± 0.4 vs. 2.6 ± 0.5, F (1.22) = 4.99, P = 0.036); 1N4R tau: 3.6 ± 0.9 vs. 2.3 ± 0.3, F (1.22) = 4.60, P = 0.043), but not in the ctx-cbl (Fig. 5, Table 5).