Microglia--a wrench in the running wheel?

Increasing the amount of physical activity has been observed to ameliorate the progression of Alzheimer's disease (AD), as well as enhance neurogenesis. Choi et al. in this issue of Neuron report that the expression of Presenilin 1 (PS1) variants, responsible for the early onset of familial AD, are capable of mitigating the regenerative effects associated with increased activity and environmental enrichment likely through changes in resident microglia and their secreted factors.