Hippocampal neural circuit mechanisms in Alzheimer's disease revealed by viral-genetic circuit mapping.

Alzheimer's disease (AD) is a progressive neurodegenerative disorder with growing major health impacts in countries with aging populations. Existing therapeutic approaches that have been based on neurochemical and neuropathological findings are largely ineffective. This lack of progress suggests we require a new framework for future AD therapies. The examination of neural circuit mechanisms in AD mouse models is an emerging focus for identifying new AD treatment strategies. We now know there are neural circuit-level maladaptive alterations in AD brains, some of which appear very early in the disease process before neuropathological features are detectable. Recent advancements in viral-genetic technologies allow us to quantitatively map the cell-type-specific neural circuit connections in AD mouse models. Monosynaptic rabies virus mapping reveals age-progressive changes in both long-range and local hippocampal neural circuit connectivity in AD mouse models - and provides explanations for human AD behavioral defects, such as sex differences and higher level visual deficits. These recent developments in neural circuits level concepts and technology present new opportunities for studying AD pathogenesis for early identification of the disease and for developing novel therapeutic interventions.