Using transgenic Drosophila models of Alzheimer’s disease, this study compared the effects of Tau and Amyloid‑β on behavioural function, autophagy gene expression and oxidative stress. Both aggregates induced behavioural deficits, autophagy gene dysregulation and oxidative stress. Treatment with the antioxidant thymoquinone improved behavioural outcomes, reduced oxidative stress and prevented Tau aggregation in vitro. The findings suggest that Tau toxicity operates largely through oxidative stress, whereas Amyloid‑β may involve additional pathways, and that thymoquinone ameliorates adverse effects of both proteins.