How the brain distinguishes memories from perceptions(quantamagazine.org)
quantamagazine.org
How the brain distinguishes memories from perceptions
https://www.quantamagazine.org/how-the-brain-distinguishes-memories-from-perceptions-20221214/
5 comments
That's a great point. Also I wonder how this pertains to flashbacks. For some reason I get flashbacks that are completely random; they occur for no particular reason (that I've identified), the memory itself can be from childhood all the way up to recent adulthood, and they have no association with any trauma or extra stimulation. For example a flashback of me in my teenage years standing at a bus stop. Fairly innocuous memory right? This issue is amplified when I consume THC; I can end up having many flashbacks while I'm high and most of them are things I haven't thought of ever since the experience occurred decades ago. I kind of appreciate them due to the nostalgia, but it's strange.
I have this strong impression that a new field, sat in between medical research and phylosophy, should be created: "introspection".
It seems to me that certain scientifical truths regarding the nature of consciousness, how we experience things, etc, can only be addressed in a subjective manner, ie. by interrogating ourselves, and reflecting ourselves, in a scientific way, on why we feel a certain way, under what circumstances, what happen if i change parameter x or y, do i still feel the same, etc...
That also sounds like heresy in terms of scientific studies but the more i read about that topic (Dennett, Penrose, etc...) the more this becomes obvious to me, that internal "thought experiments" can actually uncovered strong realities of how we think and are conscious.
It seems to me that certain scientifical truths regarding the nature of consciousness, how we experience things, etc, can only be addressed in a subjective manner, ie. by interrogating ourselves, and reflecting ourselves, in a scientific way, on why we feel a certain way, under what circumstances, what happen if i change parameter x or y, do i still feel the same, etc...
That also sounds like heresy in terms of scientific studies but the more i read about that topic (Dennett, Penrose, etc...) the more this becomes obvious to me, that internal "thought experiments" can actually uncovered strong realities of how we think and are conscious.
Always figured that was the brain clearing space for new memories and saying "hey we can delete this right?"
Not everyone suffers from PTSD (both in terms of having the triggering experience and also not developing PTSD in response to similar triggering experiences).
So while the mechanism can maybe misfire / break in some cases, I don’t see how what you’ve said counteracts the broader point here. Can you elaborate?
So while the mechanism can maybe misfire / break in some cases, I don’t see how what you’ve said counteracts the broader point here. Can you elaborate?
I was directly countering the statement that people don't get confused between them. Some people DO, and it's far more common and can be less pronounces than PTSD.
So yes, they do get confused in some cases, which supports the notion that they share a lot of wiring in the brain.
"People don't confuse this" is the part I shot down. The rest of the piece is interesting.
So yes, they do get confused in some cases, which supports the notion that they share a lot of wiring in the brain.
"People don't confuse this" is the part I shot down. The rest of the piece is interesting.
I think that’s an ungenerous interpretation that lends itself to nitpicking because it ignores the immediately preceding context.
> very strong neurological similarity between memories and experiences, we know that they can’t be exactly the same
So showing that there are cases where people do confuse the two doesn’t negate the broader point that they’re not exactly the same thing in the brain, does it?
Just to be clear, we’re talking strictly about flashbacks here, right? As I understand it that’s only one kind of symptom so I want to make sure we’re talking about the same one as others don’t seem relevant to this discussion to me but maybe you’re talking about something else.
Assuming it is flashbacks, do you know whether patients are actually unable to distinguish memory from experience structurally within the brain? Or is it more like entering an uncontrolled dream state (eg lucid dream) into a recurring nightmare? For example people have nightmares regularly of being naked in class or have a sudden exam. People while dreaming can do all sorts of complex activities like walking around. People while dreaming also have a debilitating logic and speech impediment, characteristics of PTSD flashbacks. I don’t know about whether people have actual memories appear in dreams. Still, it’s not immediately clear to me that PTSD patients confuse experience and memory vs PTSD patients have stronger memory-driven dreams on loop and are narcoleptic so enter it suddenly. In that case, It’s possible that even the one sentence you decided to focus on isn’t even wrong unless you also classify sleep with a dream pulling from memories as confusing experience and memory.
> The researchers analyzed data from the National Health and Resilience in Veterans Study, a large, long-term study of veterans of the Iraq and Afghanistan wars. They found that veterans with PTSD were nearly three times as likely as those without PTSD to report narcolepsy symptoms. When the researchers looked at brain scans of the veterans, they found that those with PTSD had significantly lower levels of hypocretin in their brains. These findings suggest that PTSD may be a risk factor for narcolepsy and that the two disorders may share a similar underlying cause.
https://sleepation.com/ptsd-may-be-a-risk-factor-for-narcole...
To me flashbacks always sounded like they probably reused dream machinery rather than actually confusing experience and memory. I believe PTSD patients are able to distinguish “I relived my trauma yesterday” from “I had the trauma happen again yesterday”.
So in summary, a) the one statement being imprecise isn’t relevant to the point being made b) it’s not actually clear to me we know that the statement is even wrong.
> very strong neurological similarity between memories and experiences, we know that they can’t be exactly the same
So showing that there are cases where people do confuse the two doesn’t negate the broader point that they’re not exactly the same thing in the brain, does it?
Just to be clear, we’re talking strictly about flashbacks here, right? As I understand it that’s only one kind of symptom so I want to make sure we’re talking about the same one as others don’t seem relevant to this discussion to me but maybe you’re talking about something else.
Assuming it is flashbacks, do you know whether patients are actually unable to distinguish memory from experience structurally within the brain? Or is it more like entering an uncontrolled dream state (eg lucid dream) into a recurring nightmare? For example people have nightmares regularly of being naked in class or have a sudden exam. People while dreaming can do all sorts of complex activities like walking around. People while dreaming also have a debilitating logic and speech impediment, characteristics of PTSD flashbacks. I don’t know about whether people have actual memories appear in dreams. Still, it’s not immediately clear to me that PTSD patients confuse experience and memory vs PTSD patients have stronger memory-driven dreams on loop and are narcoleptic so enter it suddenly. In that case, It’s possible that even the one sentence you decided to focus on isn’t even wrong unless you also classify sleep with a dream pulling from memories as confusing experience and memory.
> The researchers analyzed data from the National Health and Resilience in Veterans Study, a large, long-term study of veterans of the Iraq and Afghanistan wars. They found that veterans with PTSD were nearly three times as likely as those without PTSD to report narcolepsy symptoms. When the researchers looked at brain scans of the veterans, they found that those with PTSD had significantly lower levels of hypocretin in their brains. These findings suggest that PTSD may be a risk factor for narcolepsy and that the two disorders may share a similar underlying cause.
https://sleepation.com/ptsd-may-be-a-risk-factor-for-narcole...
To me flashbacks always sounded like they probably reused dream machinery rather than actually confusing experience and memory. I believe PTSD patients are able to distinguish “I relived my trauma yesterday” from “I had the trauma happen again yesterday”.
So in summary, a) the one statement being imprecise isn’t relevant to the point being made b) it’s not actually clear to me we know that the statement is even wrong.
>> So showing that there are cases where people do confuse the two doesn’t negate the broader point that they’re not exactly the same thing in the brain, does it?
Sure, they are different things but the author felt the need to state that they don't get confused - which is a false statement given the existence of PTSD. Since I'm bringing up psychology, I'd say ANY model of how the brain works should also account for the phenomena of transference and projection.
The author is talking about abstract (and physiological) models of how the brain works. To quote someone whom I forget "all models are wrong, but some models are useful". The EMDR model IS useful and has been used to treat millions of people. The authors model is just speculation based on some brain scans - i.e. has not been used for anything useful yet and as such I don't think we can let a falsehood like "people don't get these confused" slide.
Sure, they are different things but the author felt the need to state that they don't get confused - which is a false statement given the existence of PTSD. Since I'm bringing up psychology, I'd say ANY model of how the brain works should also account for the phenomena of transference and projection.
The author is talking about abstract (and physiological) models of how the brain works. To quote someone whom I forget "all models are wrong, but some models are useful". The EMDR model IS useful and has been used to treat millions of people. The authors model is just speculation based on some brain scans - i.e. has not been used for anything useful yet and as such I don't think we can let a falsehood like "people don't get these confused" slide.
The content of complex hallucinations reflect the person's memories and experiences. Are some hallucinations memories, perhaps composite memories, that are interpreted as sensory experiences?
i don't understand how this is relevant to the brain distinguishing memory and perception.
I believe parent is saying that PTSD is precisely a situation where memories act like perceptions; EMDR as a therapeutic modality with at least some evidence for efficacy is premised on the idea that it helps to make traumatic memories feel like memories rather than perceptions
Because the perception is triggering a memory and the memory overtakes the perception as the new reality?
>> Because the perception is triggering a memory and the memory overtakes the perception as the new reality?
Maybe more like the perception of reality is triggering emotions from a memory of a similar reality. In more extremem cases yes, it brings back the memory too. I'd argue (and this is just me) that emotions are more distinct than perceptions and memories, and are more like annotations to both. But I'm getting way outside of any clinical model I've read about. We want traumatic events to get resolved and stored without the high emotional content that distorts current perceptions.
Maybe more like the perception of reality is triggering emotions from a memory of a similar reality. In more extremem cases yes, it brings back the memory too. I'd argue (and this is just me) that emotions are more distinct than perceptions and memories, and are more like annotations to both. But I'm getting way outside of any clinical model I've read about. We want traumatic events to get resolved and stored without the high emotional content that distorts current perceptions.
> As participants recalled the images, the receptive fields in the highest level of visual processing were the same size they had been during perception — but the receptive fields stayed that size down through all the other levels painting the mental image. The remembered image was a large, blurry blob at every stage.
> [...]
> So depending on whether information is coming from the retina or from wherever memories are stored, the brain handles and processes it very differently. Some of the precision of the original perception gets lost on its way into memory, and “you can’t magically get it back,” Favila said.
This is probably more a comment on imprecise or confusing journalism than anything about the paper, but just because a larger number of early neurons were activated when recalling a memory doesn't mean the memory itself is blurry or low resolution. Perhaps the memory is just compressed (embedded) in such a way that decompressing it requires activation of a large number of early-stage neurons. This is basically how a UNet works, although UNet decoders don't (typically?) share neurons (weights) with the the encoder.
> [...]
> So depending on whether information is coming from the retina or from wherever memories are stored, the brain handles and processes it very differently. Some of the precision of the original perception gets lost on its way into memory, and “you can’t magically get it back,” Favila said.
This is probably more a comment on imprecise or confusing journalism than anything about the paper, but just because a larger number of early neurons were activated when recalling a memory doesn't mean the memory itself is blurry or low resolution. Perhaps the memory is just compressed (embedded) in such a way that decompressing it requires activation of a large number of early-stage neurons. This is basically how a UNet works, although UNet decoders don't (typically?) share neurons (weights) with the the encoder.
Ya that's the massive weakness of these studies. They always read more into their data than what's actually there.
You're basically taking a snapshot of lights in a city at night. You can't see any of the people or what they're doing, but you see a lot of lights along the waterfront. You know a shipment of freight just came in, so you make the reasonable assumption they're unloading the freighter.
But they could just as easily be dumping the tea in the harbor. There's no mechanical description of what is happening, just the observation that something appears to be happening.
You're basically taking a snapshot of lights in a city at night. You can't see any of the people or what they're doing, but you see a lot of lights along the waterfront. You know a shipment of freight just came in, so you make the reasonable assumption they're unloading the freighter.
But they could just as easily be dumping the tea in the harbor. There's no mechanical description of what is happening, just the observation that something appears to be happening.
> Could our memory of a beautiful forest glade, for example, be just a re-creation of the neural activity that previously enabled us to see it?
As one with aphantasia (and apparently a cocktail of other perceptual deficiencies), I wonder if this means that memory happens "before" perception in the pipeline? I know there's a question of whether the lack of mental imagery of aphantasia is just a "short circuit" in the brain or a complete bypass of the relevant areas, but if "memory" is just an input replay…why can I remember seeing things without activating the "I am seeing" sense?
As one with aphantasia (and apparently a cocktail of other perceptual deficiencies), I wonder if this means that memory happens "before" perception in the pipeline? I know there's a question of whether the lack of mental imagery of aphantasia is just a "short circuit" in the brain or a complete bypass of the relevant areas, but if "memory" is just an input replay…why can I remember seeing things without activating the "I am seeing" sense?
I've always wanted a more in-depth study of aphantasia beyond "we can't visualize", like whether aphantasiacs can make imagination-based value judgments even without consciously perceiving the visual. Things like "would a purple apple look appetizing? How about zebra-striped?" or "would this furniture look good in our kitchen?"
I can't usually answer these questions accurately with any confidence. Color is just something I don't care about much or remember that vividly. I have no idea which caused the other (I'd be surprised if they weren't correlated). I have preferences, but if something is the "wrong" color I usually don't mind too much as long as it serves its purpose.
I wonder if Déjà vu are in fact perceptions that get misclassified as memories.
Probably a kind of I/O virtualization.
What about PTSD? The theory behind EMDR therapy is that the experience didn't get fully processed and stored as a normal memory, but is in effect "stuck" part way where it continues to be a trigger for current inputs. The "R" is for reprocessing, which is the unstickung and storing that resolves the PTSD.