We also explored the impact of tau overexpression on motor performance using the rotarod test. Remarkably, already at 1.5 months after injection the AAV-P301S group showed a significant decrease in latency to fall from the rod rotating at 35 rpm when compared to the AAV-maxFP control group (Fig. 2b). At 7 months, the effect of tau was even more pronounced, as the latency to fall was 14.0 ± 1.8 sec in the AAV-P301S group, and 31.3 ± 5.2 sec in the AAV-WT group, both significantly different from the control group (52.5 ± 3.2 sec). In particular, expression of P301S tau worsened the motor performance of the mice, which was found to be significantly lower than the two other groups (Fig. 2b). Whereas the deficits caused by WT tau remain stable, the P301S mutant tau leads to a time-dependent deterioration of the motor phenotype, indicating a progressive pathology.