As we age, we begin to lose the connections that wire up our brains-and neuroscientists aren't sure why.

Ageing slows neuronal protein degradation in mice, leading to widespread accumulation and aggregation of long-lived proteins, particularly at synapses. As neuronal clearance declines, microglia selectively accumulate synaptic proteins, suggesting a compensatory but potentially strained proteostasis pathway in the ageing brain.