APOE and Alzheimer disease: These findings were supported by mediation analyses, including apolipoprotein E ε4 AD risk variant as a co-variate, which found bidirectional mediation of SST and AD pathology on cognitive performance proximal to death (pperm < 0.0001), but no mediation of the relationship between pathology and cognition by IT neurons (pperm = 0.31), or of IT neurons and cognition by pathology (pperm = 0.35) (results in Supplementary Table 2).