  Brains consume metabolic energy to process information, but also to store
memories. The energy required for memory formation can be substantial, for
instance in fruit flies memory formation leads to a shorter lifespan upon
subsequent starvation (Mery and Kawecki, 2005). Here we estimate that the
energy required corresponds to about 10mJ/bit and compare this to biophysical
estimates as well as energy requirements in computer hardware. We conclude that
biological memory storage is expensive, but the reason behind it is not known.
