Neuronal Vulnerability to Brain Aging and Neurodegeneration in Cognitively Impaired Marmoset Monkeys (callithrix Jacchus).

•Higher Aβ deposit and significant astrogliosis in cognitively impaired marmosets.•Activated microglia with a more complex branching in cognitively impaired marmosets.•Increased phagocytic activity in microglial cells in cognitively impaired marmosets.•Changes in dendritic spine head size and density in cognitively impaired marmosets.•Spine morphometrics correlated with the reversal learning task performance.