Fig. 4

Quantification of p-PERK+, p-eIF2α+ and tau+ neurons in each region at different stages of pathology. Cases were grouped based on their Braak stage, with stage 0 and stage I-II indicating normal cases with no or very minimal tau pathology respectively, stage III-VI indicating AD cases with mild, low-level tau pathology and stage V-VI indicating AD cases with advanced, high-level tau pathology. Across all regions assessed, the percentage of p-PERK+ neurons (a) and p-eIF2α + neurons (b) was increased in cases with Braak stage III-IV and V-VI pathology compared to Braak stage 0 or I-II. This increase was statistically significant only in the piriform cortex and CA1 region for p-PERK and in the AONb, entorhinal cortex and CA1 region for p-eIF2α. There was no significant difference in p-PERK+ or p-eIF2α + neurons in cases with low Braak stage AD pathology (III-IV) compared to high Braak stage AD pathology (V-VI) in any region. (c) Similar results were observed for the percentage of tau+ neurons. *P ≤ 0.05, **P ≤ 0.01, ****P ≤ 0.0001 compared to Braak stage 0 in the same region