Are memory updates local in mammals?
LTP and LTD are processes that operate on single synapses. We don't know how "memories" (there are several types of "memory") are encoded in the human nervous system. As a consequence, we don't yet understand the explicit link between some group of synaptically connected neurons, and a given memory.

So the short answer is "we don't know". Take a look at some of the other questions about memories in human brains: 1, 2