The decline of cognitive ability seen in some elderly people may not result from fewer brain cells, but from a rise in capricious connections.

Vincenzo De Paola at Imperial College London, Sen Song of Tsinghua University in Beijing and their colleagues observed the cell connections that shoot signals through the brain by fitting glass windows into the craniums of old and young mice. Although the researchers expected older mice to have fewer firing points, they found more. But these connections were erratic. In older mice, the connections had high turnover rates, and wavering firing strength. The older mice also performed less well on a memory test.

The researchers suggest that mental decline seen in ageing mice is due to disorderly wiring.

Proc. Natl Acad. Sci. USA (2013)