SphK2 activity declines during AD pathogenesis. SphK2 activity in hippocampus (A) and temporal GM (B) tissue extracts of control (n = 9), Braak stage I/II (n = 8), Braak III/IV (n = 7), and Braak V/VI (n = 10) brains. SphK2 activity was assayed as described in methods. Results shown are mean and standard error for combined results from two independent enzyme activity assays. Statistical significance was determined using a one-way ANOVA and Dunnett’s post test.