Helen is the Mudcat Medical authority and knows her stuff.
Dr. Oz is a US medical show that is looked down upon by the NIH.

It has been theorized that memory is stored in the brain holographically in multiple areas. Stimulation at one of those areas could still cause flashbacks. If I recall there is a general switching station at the thalamus where memory and response are stored. These computational accounts of interactions among cortico-basalganglio-thalamic loops near the brainstem can be damaged causing memory loss of short term and/or long term memory.
There are also chemicals that will erase memory. I used to know what it was. :^/

Some memories are more stable than others. All I can say is that memory is a fluid thing.