This 2014 human study showed that:

“Item memories are weakened when they are mispredicted by their context..weakening of the synapses that support the item’s representation in memory.

Note that our use of the term “pruning” is not meant to imply that traces are being deleted completely from memory.“

Connecting the dots, two studies showed that our memories are formed within specific contexts and that our memories have contexts with specific places and times.

http://www.pnas.org/content/111/24/8997.full “Pruning of memories by context-based prediction error”