In a recent post mortem tracer binding study of second generation tau tracers [18F]PI-2620, [18F]MK-6240 and [18F]RO-948 in AD, PSP and CBD patients all tracers showed similar binding patterns in AD while only [18F]PI-2620 showed a high specificity for PSP and CBD tau pathology [33] highlighting its diagnostic utility for detecting 4R-tau. This evidence concerns the gene MAPT and red-green color blindness.