People can remember things that hadn’t re-entered their mind for decades. It certainly happened to me a number of times (completely trauma-unrelated and not actively elicited).

A valid memory spontaneously re-entering your mind is different.

The idea of "repressed memories" was that people had hidden memories that they couldn't access, even if they tried. According to the theory, even if someone brought up the past event and tried to remind the person about it, they would be unable to recall it happening because their brain had blocked it out.

The idea was that only intervention by a therapist or some other special event could help the person "unlock" the repressed memories, making them available for remembering again.

What was really happening was that some therapists were leading people into "remembering" things that didn't happen through aggressive prompting and pushing, much like what happens when an aggressive investigator convinces a vulnerable person to falsely confess to something they didn't do.

I wouldn't be surprised if there are inaccessible, partly corrupted memories encoded in the hippocampus. I suspect most of them cannot be prompted by a therapist though, and likely there is no practical way to recover them.

I think it's all a matter of finding a trigger (or reference) to grab the memory. A therapist talking to you almost certainly wouldn't achieve that, but walking down the street and smelling an odd smell might.

I once found a recording of a lab session in high school physics. A day I completely forgot about. A moment that had no bookmarks in my brain.

Other things about that day were surfaced. How my braces felt and the fear I felt about forgetting a textbook.

All real, but unsurfaced until then.

That makes sense considering that human memory is strongly based on associations. Activating nearby memories can bring things back.

If you hear the first tones or words of a song you're much more likely to be able to tell the lyrics that follow compared to being asked to say those lyrics based on the title.

I think it depends on the stage of degradation and whether the network is still connected to something that can interpret it.

This is a more precise statement than just "you can recall things you thought you forgot".

It is specifically about trauma, and generally you don't forget traumatic events and that's often a big part of the problem. We are not talking about trivial things like the name of your maths teacher in high school, which have a tendency to come and go.

It is also specifically about therapy, that is an environment where you are actively encouraged to recall memories. We know how easy it is to make up memories, especially with the help of a third party (here, the therapist).

Combine the two: memories that are hard to forget and an environment conductive to making false memories and it becomes very likely that the "lost" memories are completely made up.

> and generally you don't forget traumatic events

That depends on how many you endured really. Only so much room in the old noggin with everything else important going on.

>It is specifically about trauma, and generally you don't forget traumatic events and that's often a big part of the problem.

Oh, of course you can.

My guess is that long term memory recovery is inherently a reconstruction from the pieces that you have retained. So it is not unlikely to include dreamed up parts.

The debunked recovered memory therapy was something different: They would use different techniques and leading questions to try to get a patient to think they remembered something that may not have happened at all.

Some of the techniques included hypnosis or even giving the patients (including children) sedative-hypnotic drugs before pressuring them with the leading questions.

If they could eventually get the person or child to claim to have some memory of the event (after asking a lot of leading questions and maybe even drugging them) they considered it to be a recovery of the memory.

This has been my experience as someone who has experienced childhood trauma, and what I've inferred from my therapist. He taught me that the memories I have are typically exaggerations of what happened and it's hard to pin down what truly happened. The only evidence I have that has any merit is my siblings can corroborate with similar experiences since it happened to all of us, and I'm sensitive to things related to these traumas. Almost every day I can feel the things that happened, and on my worst days these areas are much more sensitive.

On top of that, I have legitimate memories that were not traumatic, but still related to the same traumas because said person attempted to encourage these activities throughout my young life on rare occasions. I didn't remember what happened as a kid, but I knew something wasn't right and I wasn't comfortable. It wasn't until I was almost 30 that I had my first "flashback" which was a fractured memory, I still remember it looked like a faded photograph in my mind, and it was accompanied by an extremely uncomfortable feeling.

The re-surfacing memories aren't real in a sense, but in my case they aren't entirely fake either.

I wonder if it's possible that things can be completely imagined with absolutely no basis what-so-ever in certain circumstances, and I also wonder how difficult it is to discern that. It seems to be a difficult concept to manage.

The accuracy of recollection can certainly vary, but the point is that some information is retained long-term even when it isn’t made use of in the meantime. Of course one could argue that actually it is being made use of unconsciously, but I’m skeptical of that, given the relative irrelevance of the details that can be recollected. It’s also not that difficult to imagine that some memory-representing micro-structures in the brain just happen to be stable over decades even when they remain untapped.

Indeed. I was browsing a Nintendo fan site I made in 1998 on archive.org when I was just 11 years old. I don't remember every detail about making it, but my brain had no problem stitching all the pieces it did retain back together.

On the other hand, I do have some Gandalf "I have no memory of this place" moments for other things.

They won't remember it accurately anyways, so it's kind of a moot point.

Though you're right - a specific scent can easily call up an ancient, forgotten memory.