APOE and Cognitive impairment: In addition, neuronal taxa (excitatory and inhibitory neurons) with high ApoE expression are strongly associated with pre-disease (i.e., mild cognitive impairment stage), while this correlation decreases after disease (i.e., AD dementia stage), and as the disease progresses, a large number of ApoE-expressing neurons decrease with disease progression (Ignatius et al., 1986).