Which term refers to the hypothetical brain changes associated with the formation of a long-term memory?

Answer is memory trace or engram. These are theorized way by which our memories are being stored through biochemical changes in the brain usually in response to the external stimuli. The presence of engrams shows how memory persists and stored in the brain. This strengthens the connection of each group of neurons The result of transient or enduring changes in the brains are engrams. This is considered as the representation of memories in our brain. A cue in retrieval can induce a pattern of activity. If this is similar pattern to the previous one you can remember the event.