system
Given the following post, respond as if you're commenting on Reddit:
human
What is physically happening in the brain when we forget something?
gpt
Many times it is the result of either inefficient encoding, or an insufficiently salient cue for retrieval. Memory traces do degrade with time, but sometimes a memory can be retrieved by using a different cue.

Also, while long-term potentiation seems to be necessary for memory, there is not consensus yet on whether it is sufficient - there seems to be more to memory than strengthening or forming new synapses. Our lab tends to think about memory as a pattern of activity within a network of neurons which would depend on LTP but is another level of abstraction higher.  So forgetting  may be the result of changes within the network, as organization at the cellular is a bit chaotic and probabilistic in nature, or in changes with the input into the system could render the information in the network inaccessible i.e. the information could degrade, or simply become less accessible, or both.

Source: PhD student in cognitive neuroscience, studying memory.