Acute silencing uncovers multiple forms of activity-dependent neuronal survival in the mature entorhinal cortex

Neurodegenerative diseases are characterized by selective vulnerability of distinct cell populations; however, the cause for this specificity remains elusive. Many circuits that degenerate in disease are shaped by neural activity during development, raising the possibility that mechanisms governing early cell loss may be misused when activity is compromised in the mature brain. Here we show that electrical activity and synaptic transmission are both required for neuronal survival in the adult entorhinal cortex, but these silencing methods trigger distinct means of degeneration in the same neuronal population. Competition between active and inactive cells drives axonal disintegration caused by synaptic inhibition, but not axon retraction due to electrical suppression. These findings suggest that activity-dependence may persist in some areas of the adult brain long after developmental critical periods have closed. We speculate that lifelong plasticity required to support memory may render entorhinal neurons vulnerable to prolonged activity changes in disease. ### Competing Interest Statement The authors have declared no competing interest.