The process that changes the brain in a fixed and stable way that establishes events in long-term memory is called

consolidation

Explanation:

Consolidation is the process by which short term memory can be converted into long term memory. It is achieved by rehearsal and meaningful association. This process stabilizes a memory after it has been acquired. It is made of two processes, synaptic consolidation and system consolidation.

Synaptic consolidation occurs first few hours after acquiring the memory. System consolidation occurs over a period of weeks to years and in this process hippocampus dependent memories become hippocampus independent.

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