MAPT and Alzheimer disease: A significant reduction in the total Layer 5 neuronal population was seen in all FTD donors compared to controls (F[4] = 3.53, p = 0.01; FTLD‐TDP: p = 0.03, FTLD‐tau: p = 0.04, FTLD‐FUS: p = 0.01 and AD: p = 0.66); however, when grouped based on genetic status, only tau‐MAPT donors and those with FUS pathology reached significance (p = 0.05 and p = 0.01, respectively) (Figure 2E,F).