MicroRNAs in Learning and Memory and Their Impact on Alzheimer's Disease.

Learning and memory formation rely on the precise spatiotemporal regulation of gene expression, such as microRNA (miRNA)-associated silencing, to fine-tune gene expression for the induction and maintenance of synaptic plasticity. Much progress has been made in presenting direct evidence of miRNA regulation in learning and memory. Here, we summarize studies that have manipulated miRNA expression using various approaches in rodents, with changes in cognitive performance. Some of these are involved in well-known mechanisms, such as the CREB-dependent signaling pathway, and some of their roles are in fear- and stress-related disorders, particularly cognitive impairment. We also summarize extensive studies on miRNAs correlated with pathogenic tau and amyloid-β that drive the processes of Alzheimer's disease (AD). Although altered miRNA profiles in human patients with AD and in mouse models have been well studied, little is known about their clinical applications and therapeutics. Studies on miRNAs as biomarkers still show inconsistencies, and more challenges need to be confronted in standardizing blood-based biomarkers for use in AD.