To verify the role of the expression of NOX4 in the DG in the cognitive impairment observed in the PD animal model, selective inhibition of NOX4 was achieved via the stereotaxic delivery of an adeno-associated virus 2 (AAV2) containing an shRNA targeting NOX4 to the hippocampal DG (Figure 6a,b,c). This evidence concerns the gene NOX4 and Parkinson disease.