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Practical Facts about the Human Brain (leowid.com)
396 points by LeonW 27 days ago | hide | past | web | favorite | 71 comments



I wish people would be more skeptical about their recall of memories.

In particular I wish people would stop thinking their memories are especially accurate if they were especially "vivid".

https://en.wikipedia.org/wiki/Flashbulb_memory


I agree. Memory biases may either enhance or impair the recall of memory, or they may alter the content of what we report remembering.

There are many memory biases including the humor effect, positivity effect and the generation effect.

The humor effect states that humorous items are more easily remembered than non-humorous ones.

Positivity effects states that older adults favor positive over negative information in their memories.

Generation effect states that self-generated information is remembered best.


How universal are these biases? Anecdotally, I feel as though i have a stronger recall of negative experiences than equivalently good ones. If that is a thing, i wonder if it might be due to, or perhaps a cause of, depression.


> Anecdotally, I feel as though i have a stronger recall of negative experiences than equivalently good ones.

It is the same for me, but I noticed I was the odd one, almost all around me follow the 'rule': they forget about most of the hardship, remember the good parts, and even assimilate the good parts for the whole experience.

It was especially noticeable a couple of years after school. My student mates and I started studies through a tough school (very intensive, exhausting, an unbelievable amount of work, not a minute of rest, rough teachers and discipline, lots of pressure), and we went through the same thing. But like 5 years after we escaped from there, they spoke of it only as a great experience, which was lots of fun. That sounded incredible to me. They had forgotten about all the bad times, which happened 10 times more often than the good ones. The 'great experience' I could understand a bit (it's normal when you have finally overcome something difficult to feel proud of it, and it also made you stronger, if it didn't break you); but 'lots of fun' it really wasn't. Ever. And I couldn't understand either that all the negative points had vanished in their mind.

I was about to add that I have always been more (now) or less (20 years ago, in those student years) on the depressive side, and that it could be related, but I read that you made the exact same theory in your next sentence! So it seems we are in this same bag:

> If that is a thing, i wonder if it might be due to, or perhaps a cause of, depression.

I came to think that depression make you see the world as it is, and not the version the world which is numbed by the 'drugs' which a normal body/brain produces and which blur the vision as rose-tainted spectacles do (anecdote: I have rose/orange-tainted cycling glasses and that's exactly the feeling some days when I take them on/off!) .


biases generality is a great question to ask. I rely on smarter people than me quoting repeated and repeatable research. The best I've ever read is in the book Thinking Fast and Slow, and a beautiful representation of it can be seen on designhacks.co (the latter is on my wall as a reminder of how fallible the mind can be).


I think the better question to ask is, what kind of memory? Research I cannot conveniently find at the moment shows that raw declarative memory is improved under trauma. For example, most people who were old enough, nationwide, can recall where they were and what they were doing on 9/11. Other kinds of memory, like skill automating (e.g. playing the chords effortlessly on a guitar or mastering the core grammar of a language) are much harder to do when you're under stress.


Interestingly, though, it often turns out that recalling "where they were and what they were doing on 9/11" is very often wrong. And that when you're wrong, you're more certain you're right.

Malcolm Gladwell did a very interesting podcast episode on that: http://revisionisthistory.com/episodes/24-free-brian-william...


Indelible in the hippocampus


Hi everyone, Leo here. I feel grateful for the HN community's response to this post. I only emerged recently to the "real world" again and feel still some hesitation and fear around showing a much more vulnerable part of myself with the work I do now. (Building marketing software was fun too!) So yeah, just want to say thanks and would love to discuss anything this sparks.


1) "80% of your body’s signals are sent to the brain from the body and only 20% the other way around."

This is pretty interesting. The idea of not attempt to "command" the body but work with the body and unconscious process is common in a wide variety of martial arts and healing art modalities (Alexander Technique, Qigong, hypnosis, etc).

2) "When your amygdala is active, you can’t have empathy for others"

Unfortunately, this statement seems to suffer from the weakness of popular psychology expositions - a series of fairly pat cause-and-effect statement when the causes of virtually all behavior is more complex and much less certain.

The human brain is fantastically complex thing. Neurologists and psychologists have done many experiments on it. The "replication crisis" is a good indicator how difficult is to go from experiments on a few particulars to a general understanding of how the brain works. I think the criticism of "functional areas" that Luria made in The Working Brain should be read carefully.

The thing about this is: neurological research is great to add if what you're looking for is "what might be", using methods that possibly have scientific and seem effective. But if you operate in terms of "how things absolutely are", then one risks going into the realm of pseudo-science. And there's a lot of supposedly neurologically based new age quackery out there - much of it based things that "the latest findings" whenever said quack happened to get their start.


Thank you.

There is some stuff in post that is somewhat useful, but the conviction of the statements is a bit much. Nothing in the brain is simple, and most of neuroscience is in it's infancy today. Dandy-Walker syndrome is an especially extreme, but illustrative, case of how strange the brain can be on the inside, yet present as normal on the outside[0].

[0] https://en.wikipedia.org/wiki/Dandy%E2%80%93Walker_syndrome


In the majority of individuals with Dandy–Walker malformation, signs and symptoms caused by abnormal brain development are present at birth or develop within the first year of life

Doesn't seem like "normal" presentation to me.


https://en.wikipedia.org/wiki/Hydrocephalus#Exceptional_case

"The person was a married father of two children, and worked as a civil servant, leading an at least superficially normal life, despite having enlarged ventricles with a decreased volume of brain tissue. "What I find amazing to this day is how the brain can deal with something which you think should not be compatible with life", commented Dr. Max Muenke, a pediatric brain-defect specialist at the National Human Genome Research Institute. "If something happens very slowly over quite some time, maybe over decades, the different parts of the brain take up functions that would normally be done by the part that is pushed to the side.""


2) I enjoy the truism that we cannot act lovingly when we are on the defensive. It's more abstracted from the biology, but perhaps that helps it capture the nuances of reality.


Its very interesting to me that you have achieved the financial success that many dream of, which could allow you to retire and do what the heck you like for the rest of your life. But somehow it didn't bring total happiness, so you have actively gone on a mission to seek that out.

Maybe that is a warning sign for many people aspiring to make money, that even fully loaded you still have to deal with your own brain. Knowing how your own brain works and how to make yourself happy is a very important skill.


Couldn't have said it better myself, that's exactly been my experience and what I'd like to share with others both experientially in sessions and through my writing. And I'm having a lot more fun just being with all aspects of life from a human connection perspective leaving the striving, money, etc., on the side (even though it's hard and creeps back in).


To quote Rodney Dangerfield when asked if becoming successful has made life better: "You've still got the same head"


This post resonates a lot with me, in particular items 7 and 2. I subscribed to your newsletter and am looking forward to future content!

That being said: in my personal experience, having an intellectual understanding of something (like emotional triggers being unintegrated memories) provides some brief relief, but rarely helps me make behavioral or emotional changes in the long run. From your point of view, what is the relation of knowing vs experiencing in making progress towards emotional resilience, and what techniques can you recommend for the experiencing aspect?


Thanks for the support!

Yes, I try to strike a balance with that. To me, knowing about it brings me a lot of safety, so I know what I'm getting into when I'm doing a session, crying, contorting, reliving old memories, etc. Ultimately, I agree with you, we can talk about how to ride a bike with as much detail and scientific evidence as we want, eventually we need to ride one to see what its like.

The most effective methods I've experienced were Somatic Experiencing, a body-based psychotherapy practice I've also trained in as a therapist. There's also an empathy resonance approach by a woman called Sarah Peyton that I find very effective (her book "Your resonant self" is great). Of course I believe in my own methodology of emotional resilience which is sort of a mix of the two above, I'd be glad to offer a free session to you anytime to experience it.

Ultimately there're lots of methods, like meditation, yoga, therapy modalities that try to accomplish what we're intellectually talking about when we say emotional resilience or inner healing. In my experience this is only effective whenever the practitioner has studied and experienced this on their own body and nervous system to offer it to you effectively. And that's hard to know when it's the very thing you're looking for and you only know it intellectually. A bit of a catch 22. And it's not really a requirement when you go to therapy school for example. So it can be a mixed bag. Trial and error, which can be painful when you open yourself up to these aspects inside yourself is your friend too I believe (I tried talk therapy, various meditation practices and a few others and settled on what was both most effective in my personal experience and had the most scientific backing, like the methods I described above).

Finally, I think we're all equipped as humans to offer co-regulation and empathic presence to each other to heal from whatever difficult or stressful experience we've had. Most of us just have unlearned it very young or there's not enough emphasis in our environment to practice that with each other.

Hope some of that is helpful, let me know if you have any more questions!


Loved your post, would love it even more if you included some citations to back up the Neuroscience claims.


thanks! Yeah, I tried my best to link throughout the post. I can see how having the citations neatly at the end may be helpful too if that's what you're saying!


> 80% of your body’s signals are sent to the brain from the body and only 20% the other way around.

So whenever we are afraid or anxious and we feel that thing in our bellies, is it the brain sending messages to the belly or the belly reacting and sending messages to the brain?


Most of the time its a mix, it creates a positive feedback loop, which isn't really so positive, but it can be! Say your gut is tight, it sends a signal to your brain saying "I'm tight", now the brain receives this and reinforces it (the other 20%) by saying, "the gut is tight, we need to keep it tight!", which makes it tighter and the cycle continues. Does that make sense?

If we're in a grounded, reflected and self-connected place (i.e. if we have empathy or warm accompaniment from ourselves or someone else), we can interrupt this cycle. The signal "the gut is tight" from the gut can be discerned "ah, interesting, I wonder if it needs to be tight or if I should change the topic or watch a different movie or leave this room", etc.,


Right, but how does the gut know it has to get tight?


Yes, this happens through a process that Porges calls "neuroception" (easy to google). Essentially the subconscious part of your nervous system, especially the brainstem constantly scans your environment for threats of any kind (it takes in incredible detail, some say 1000s of times per second without it ever bubbling up to your conscious mind).

Here's an example: You see a tiger in the forest. Your eyes send that signal through their nerves to the brainstem, which makes your stomach tight and activates your legs to run away. The tight stomach and running legs then send their signals of movement and clenching back up through to limbic system ("I'm scared!") and the neocortex (your conscious brain, "I'm running away from the tiger!") to tell it to run. Because all of this happens so fast, our experience is this: We saw the tiger and therefore we're scared and are running away. That's not really what's happening under the hood, we're scared BECAUSE we're running and have a tight gut, the tiger was just a trigger for the brainstem/gut/legs. Makes sense?


My current understanding of this, combining thoughts on subsumptive robotics and embodied cognition:

Emotional states aren't reified in the brain; they're reified in our physiology. When you're happy, or sad, or scared, or whatever else, that's not a fact about your brain; your brain is just perceiving a fact about your body. (A fact that it worked together with the body to create, but still.)

Think of the brain as the CPU and the body (muscular contraction levels, etc.) as RAM. The brain-as-CPU has registers (informational state held directly in the brain), but your emotions are not held directly in such registers. Emotional states are, instead, patterns of information in the body-as-RAM, that the brain-as-CPU (statelessly) perceives [loads from, polls] in an ongoing way. If the body-as-RAM is polled and shows a certain recognizable pattern of activations, then that is interpreted by the brain as a certain emotional state.

Both the brain-as-CPU and various body parts (devices on the bus) can write to the body-as-RAM. The brain-as-CPU will then notice that the "emotional state" that it reads from the body-as-RAM has changed, and may do something about it (reinforce the change, counteract it, etc.)

What you experience as the qualia of emotion, is the brain's perception of the body-as-RAM, the same one it uses to decide whether to "do something about it."


Thanks I'll check that out!


Hi LeonW, I was born in Bozen, I use your software, and I practice meditation every day. I work at a startup where we try to keep stress low in a friendly environment.

Wanted to say thanks, nice article, and you are very brave to open up that way ;)


Thanks man! Feel the love over here in the woods. If I can support you or your company with anything, please reach out! (l.widrich@gmail.com)


I found the article very very nice. Concise form but new content (medical field is so vast it takes ages to gather integrated knowledge).

Thanks a ton.

ps: it's on reddit a few times (I found it so useful I pushed it to a very large one)


Hi, not a neurologist here, but it doesn't take more than 5 seconds to realize that everything you wrote in here is wrong. Have you considered deleting it?

Edit: Specifically, vagus nerve as cause of emotion, amygdyla+empathy, synapses vs skills, everything about "feigning death", everything about "triggers"...


“What is my body trying to tell me with that tight stomach, sunken heart, clenched shoulders?”

I have been reading Radical Acceptance by Tara Brach and this is one of the themes that keeps repeating in that book and in general in meditation. To understand one's mind and the root cause of an emotion one need to focus the attention on how one's body feels and what it's trying to say. While meditation is now widely accepted as beneficial, I have generally been less accepting or even dismissive of the surrounding teachings and method. I think it's time to revisit my views and be more open to it.


I’ve had a similar experience. I think the reason is that there’s a lot of noise in the field. A ton of low quality thought and half baked ideas or pure nonsense.

But that really should not close one off to reputable sources like Tara Brach (highly recommend people start with her guided sessions which are available free on her site) who have a well of experience honed over the years.

One time in India, some family members took me to an astrologer. I was extremely skeptical but this person was famous in town and well known regionally as well. And when I voiced my concerns that the whole field was all hocus pocus, one of my relatives said that may well be true for many individual practitioners in the field, but if you think about it as a person communicating to you using their own finely tuned heuristic for outcomes, it’s a different story. Maybe the more reputable sources in these fields should be thought of in that way, where you shouldn’t expect perfect accuracy but you should use their thoughts and knowledge as a rough guide to a kind of knowledge we have very few tools to directly explore rather than pure truths.


Pure truths one of the most important tools in developing self-knowledge. IMO going to an astrologer is akin to using a prostitute blindfolded.

You want to understand yourself, spirituality or even the universe? Study the laws of nature, the 112 names of Shiva, the 72 names of God, 613 Mitzvot of the Torah, the 4 worlds and 125 degrees of Kabbalah etc. etc. etc.

Heck, study the alphabet and how to write and pronounce it. Ladders abound. Just pick one that seems like a challenge, and then pick a fun method of studying it. I like to mix calligraphy and pronunciation practice in.


I'm not familiar with Tara Brach, but I don't think your comparison is doing her much good.


Yes, I'm a big fan of Tara Brach's work too! My experience has been that many of us live in such a cognitively focused world that the sensations and feelings of our bodies take a huge back-seat.


On Amazon, I'm seeing 'Radical Acceptance: Awakening the Love that Heals Fear and Shame' from 2003 and 'Radical Acceptance: Embracing Your Life With the Heart of a Buddha' from 2004. Is the newer edition much different, apart from a presumably more fashionable subtitle?


"While meditation is now widely accepted as beneficial"

No offense but your claim is absurd. Other than placebo effect, there are no accepted benefits of "meditation" (whatever that means) within the scientific community.

However in the new age, gluten-free communities...



Based on the descriptions there, it doesn't seem to me like the mentioned studies actually show meditation causing a clear benefit. That's not surprising to me, since most studies on meditation (like most lifestyle studies) fall into one of:

1) only describe observational correlations, not causation (such studies are useful for guiding further research, but are a poor basis for recommending lifestyle changes)

2) describe an intervention leading to a statistically significant change, but one whose practical significance is negligible, unsubstantiated, or an unclear mixture of benefits and drawbacks

3) quality too poor to draw any firm conclusion at all (too small, no control group, neglect of known likely confounders, blatant p-hacking, etc.)


I’m sure medication is very helpful for some people, maybe it’s great for everyone. But posting a Wikipedia link that anyone could edit, not exactly hard hitting science. Maybe find one of the referenced papers and read it to see if it makes your point?


You seem pretty defensive for someone that can be proven wrong by a 30 second Google.


I upvoted because I like to see popularizations of results from neuroscience, but I would also caution against cherry picking papers and placing interpretations atop them.


> caution against cherry picking papers and placing interpretations atop them

I worry about this every time I read a "practical" article about the brain. Can anyone tell if the main points in this article is generally accepted in the scientific community?


I'd save yourself the trouble and throw it all in the garbage.

>Feeling heart-broken? Feeling angry and frustrated? Feeling sunken and collapsed? Feeling energized and happy? All of these feelings will have had their origin as sensations from vagus nerve.

This is a fundamental misunderstanding of everything to do with neurology. There is simply no way to write a point by point rebuttal of how much is wrong in this article.


Wow.. I had read through diagonally and missed this one, otherwise I would’ve been a bit more negative.

The real shame is that reading about the different systems that do give rise to these feelings is actually really interesting.


The "active amygdala = no empathy" point does not jibe with my lay understanding of the physical phenomenon of empathy.

That's the only one that I don't believe models our physiology in a useful way. The rest match up with some of the stuff I've read/watched.

Watch some videos by Robert Sapolsky on YouTube. He's a neurostuff prof at Stanford. Good presentations.

There's "Why Zebras Don't Get Ulcers" https://www.youtube.com/watch?v=D9H9qTdserM

Also an actual academic lecture on the Limbic System which contextualizes & clarifies some of the other assertions in the OP blog post. https://www.youtube.com/watch?v=CAOnSbDSaOw

There are more but hopefully YouTube's algorithm helps you out there. The Stanford lecture series is very interesting though Sapolsky doesn't deliver all the lectures.

edit: The only plausible, good faith explanation of the amygdala-empathy claim I can think of is that there are facial recognition studies designed to activate the amygdala https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4979579/ that showed some correlation between anxiety levels and ACC-amygdala connectivity. The ACC, or anterior cingulate cortex, is held to be responsible for empathy. So it may be an interpretation of that knowledge the author is talking about. I know that facial recognition tests are used for evaluation of empathy, sexual attraction and so on. This is probably the kernel of accuracy in the claim.

Or there may be other science on the topic that reaches a conclusion closer to what the author said.

The linked study is extremely interesting read.


Yes, take for instance: "2.) When your amygdala is active, you can’t have empathy for others"

Leo provides no source for it, and most importantly it sounds like an overly simple model ("your amygdala takes over, and you can't feel any empathy until it's no longer active"), and overly simple models tend to be very wrong when we're trying to describe such complex mechanisms as that of our brains.

Taking research papers and drawing conclusions and interpretations without formal training, in an authoritative manner, can lead to a lot of inaccurate beliefs about the world that people might carry to their grave because they think they're backed by science.


Also...

>When a synapse strengthens, its neighbors weaken

Again, author draws nonsense conclusions based on this about skill learning. A synapse is not a skill.


Same here.


My simplified main takeaway from this post is: chronic stress seems to be at least as bad as chronic alcoholism [1] and therefore we really really need to be masters at the art of relaxation.

The two forms of evidence that stood out to me: (1) the effect of an overactive amygdala and (2) the negative effect of stress on the neocortex.

[1] Alcoholism isn’t mentioned in the post, that’s my own interpretation of the potential damage it can go. I’m going to do an online search for it to see whether that comparison has any merit.


I'd caution against taking anything in this article as truth. This is written by a self help guru, not a neurologist.


I know, fortunately I know enough neuroscience to know to what extent I should believe this.


I am also a believer in getting out of crappy situations, for example a bad job. Sure you can meditate to calm yourself down every day, but sometimes the situation needs to change.


> Feeling heart-broken? Feeling angry and frustrated? Feeling sunken and collapsed? Feeling energized and happy? All of these feelings will have had their origin as sensations from vagus nerve.

I thought emotions can from the limbic system?


Emotions come from the entire body, as interpreted by the insular cortex (internal sensation) and cingulate cortex (internal motor planning).

I'd have to check the source, but I'm pretty damn skeptical on all interoceptive information flowing through the vagus nerve. I'm pretty sure my adviser has told me that's Just Plain Wrong.


I wonder how it is determined which neurons send signals "to" vs. "from" brain. This 80/20 to/from split is surprising.

The reason I'm asking is because sending electrons up a wire isn't the only way to signal with electricity. When the output that was high-impedance suddenly opens up, allowing you to send electricity through, that actually can be a signal to you, that something on the other end has changed.


Neurons can be understood to be fairly directional. There is no direct electrical connection between neurons: there's actually a small gap between the upstream neuron and the downstream neuron. When the electrical signal reaches this gap, the up-stream neuron releases a chemical signal, which is processed by the down-stream.

So the state of the up-stream neuron depends very little on the down-stream neuron: if the down-stream neuron is in it's refractory period and can't process the chemical signal, the up-stream neuron can still fire all day, and the chemicals it releases will essentially fall on deaf ears.

That is a somewhat simplified view, and there is such a thing as retrograde signaling (chemical messaging from the post-synaptic neuron to the pre-synaptic neuron), but it's believed these signals have less to do with the primary flow of information in the brain, and probably relate to slower processes like modifying the strength of the chemical signal in the affected synapse.


"When your amygdala is active, you can’t have empathy for others"

This is an excellent example of those aspects of our existence that are deterministic. No matter your willpower, you may be bound by biology to act a certain way. Part of being a good person is to recognize these deterministic effects and plan your life accordingly.

For example, if you get "hangry" often, keep a food item on hand at all times so that you can address your hunger before you say something mean to your partner et al.


bound may be too strict, plasticity allows for reshaping your emotions, senses, how you process them


I suppose that falls under "Part of being a good person is to recognize these deterministic effects and plan your life accordingly."

The type of "reshaping" you're referring to would go beyond willpower in a single moment. Probably something like cognitive behavioral therapy?


Yeah CBT is in that box and it's indeed not a oneshot effort more like a year-scale (if not decade) process. The ideas aren't that complex, but like music .. it's subtle and requires life experience.


> 2.) When your amygdala is active, you can’t have empathy for others

I'm curious is this is a mechanism behind social anxiety. In some social situations I very clearly lose the ability to think - all thats left is an empty mind and my body going through the motions. Its completely different than my regular way of living (from my perspective, maybe not from other people's perspective) but definitely makes it more difficult to connect with others and build friendships.


> When your amygdala is active, you can’t have empathy for others

Do being late for something and driving in traffic activate the amygdala? I think I can feel that combination drain my empathy. I'm trying to actively avoid those two things. Anecdotally, it sure seems to have a similar effect on quite a few others too.


> I went to live in buddhist monasteries for a few years. There I was able to turn my focus away from outside of myself towards my own body, feelings and inner world.

That's from their Main Story.

I'm trying to tell myself that I can think effectively as long as I'm in focus.


Would have been better form to more substantially attribute Stephen Porges' work here, only a small mention is placed under his chart.


Great point, I feel incredibly indebted to Stephen Porges', both for my own internal well-being and the lessons I've learned and can share with others.


So, 2. + 5. + 6. might be the sources of bipolar disorders? Brain chemistry out of balance means that activation patterns are being modulated differently than before, and stress causes that in one way or another. Changed modulation might trigger changing/cycling states of peace or alertness, shrinking or widening associative activation. But why are some people more susceptible to stress than others? What is different?


Bipolar is not related to stress disorders. Please don't try to use this article as a primary source, because it misinterprets everything and tries to put a "self-help" spin on it, which is just going to confuse you more.


Why are you patronizing? And what are "stress disorders"?


Haven't read it completely, but hoping it has something related to guts' connection with brain




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