Evolution doesn't try to head towards any global optima, so it is quite believable that certain things just don't work a certain way even if they sound 'obvious' to rational beings.
> Evolution doesn't try to head towards any global optima
If one even exists. I don't think you could actually say a global optima exists in a lot of cases. Since there are a lot of compounding factors and the functions aren't required to be continuous.
And teeth. And corneas. There are quite a few things that only last long enough to get you sufficiently past child bearing age.
Of course, old people can learn new things so I always thought the "neurons don't grow" thing was silly (although I guess it's possible that we have a set number of neurons and it's just our synapses that keep growing).
Do teeth regenerate? A quick search for 'tooth enamel regeneration' turns up a bunch of pages saying it can't regenerate, and a couple about some researchers who found some treatment which does let it regenerate somewhat. I hope you're right, though.
Auditory hair cells in the inner ear -the ones that allow us to hear sound- do regenerate in many animals but this mechanism fails in mammals. The surrounding cells try to replace them but something goes wrong and they die. This is why hearing loss is permanent, and exemplifies how stupid evolution can be at times.
Are there estimates of how long it would take for humans to evolve to regenerate those cells - if specifically selected for it? Are we talking thousands of years, hundreds of thousands of years, or are there likely people alive today already that have the necessary mutations?
I'm no expert, but there are many papers from 10 years ago where they identified a signaling gene whose concentration was not being raised enough for the neighboring cell to divide and replace the hair cell, and it was claimed that in 10 years hearing loss would have a cure. We seem to be more or less at the same point though, because it is not clear what goes wrong in the signaling pathway, or whether if that is the only issue. IMO too little is known to answer your questions.
Evolution, AFAIK is just a random mutations happening here and there. If they bring some advantage (which good hearing in later age definitely should, but then again it covers mostly later age), harshness of life should eventually select those individuals as better survivalists.
Apparently whatever mutation happened in the past in this regard was not good enough / human still didn't survive, or it didn't happen yet. It might be funny if we discover some remote tribe actually has this regenerative mutation.
I think its question of time (maybe very long time), look at our unique ability to process lactose in adult age.
Anything that happens after the end of an individual’s reproductive years (perhaps also the period of raising the offsprings) stops exerting any evolutionary pressure. The fact that you have a “defect” at old age no longer blocks you from transmitting it so it can propagate through generations without evolution selecting against it. Random mutations “fixing” the gene can occur but still have to compete with the overwhelming number of non mutated “defective” genes.
> Anything that happens after the end of an individual’s reproductive years (perhaps also the period of raising the offsprings) stops exerting any evolutionary pressure.
This is definitely wrong. Individuals (e.g. grandparents or just random society members) can influence survival rates of other society members.
Some species(e.g. ants) even have sterile members that definitely exert evolutionary pressure.
I think you didn't take enough time to understand my point before being so "definitive".
Sterile ants do not exert evolutionary pressure unless they would attack weak queens before they are ready to reproduce. Evolutionary pressure (by scientific definition) is caused by things that reduce reproductive success in individuals or parts of population. Like a mutation that reduces fertility. Having the old individuals around might help relieve some of the pressure by infinitesimal amounts (helping raise offsprings) but that's about it. They cannot influence the outcome of a "defective" gene so they do not really drive evolution in any meaningful way.
Take this example. A genetic disorder that causes blindness soon after birth basically eliminates the individual from the population and the genetic defect along with it. Thus evolutionary pressure (genetic defect before the reproductive age) achieves the selection.
A genetic disorder that causes blindness at old age, any time after the next generation was raised, might also eliminate the individual but this doesn't matter as much. The gene already got passed along to the next generation(s). As long as it manifests only after reproduction then it does not reduce reproductive success, so exerts no pressure.
Or perhaps you want to take something like male impotence as an example. If humans were expected to bear offspring only in our 70s I'm certain Viagra wouldn't be a thing. Only the males that are still able to perform at that age pass along their genes, to the point where the males that can't are the exception.
I hope you can appreciate the difference in magnitude (many orders) between directly applying evolutionary pressure by removing the individual from the gene pool before the gene can be transmitted, and indirect evolutionary pressure via reduced support in society (which could conceivably affect reproductive success). For one, it stands to reason that solitary species or ones that do not form real societies would be completely unaffected by this indirect evolutionary pressure.
The case in point is the sciatic nerve is massive, and prone to constant stresses and strains, yet supposedly never regenerates.
Sciatica doesn't generally show up until people are in their 40s-50s. This is long after childbearing years for most people. At that point your sciatic nerve has done its job and gotten you across the finish line. What happens next is less important.
Less important but your fitness is still relevant in terms of survival of the tribe, which is selected for since it affects the survival of any one individual.
50s you can still be pretty strong and endurant, provided no accident/degenerative disease happened. I would expect tribe of anybody but mindless savages would often protect their older if only due to their experience in survival (but maybe we were pretty much mindless savages during most of our evolution). 60s is when any remaining strength takes nose dive
Based on the data from modern hunter-gatherer populations, it is estimated that at 15, life expectancy was an additional 39 years (total 54), with a 0.60 probability of reaching 15.
I believe the cells in your eye's lens are not replaced. New cells are added around the outside but the old ones are never taken away / broken down. This is why our lenses become cloudy and more rigid in old age.
That is a compelling argument. But, if you Google for "heart cells don't regenerate", you find that it does appear to be a thing experts believe. And you find article like this that attempts to explain why heart cells can't regenerate: https://www.sciencedaily.com/releases/2011/08/110809092102.h...
Some studies on the .. axolotl ? (limb regrowing salamanders) showed that human had similar capabilities BUT with a very fast bailout mechanism that stopped the regeneration a lot earlier.
I had some nerve damage a while back and went to a neurologist. He did an EMG test (https://en.wikipedia.org/wiki/Electromyography) and confirmed the nerve was damaged. He used electrodes to show that it did not conduct electricity like it was supposed to, nor did it conduct electricity like the corresponding one on the other side of my body. (Somewhere, I have a printout showing voltage and latency numbers.)
He then told me that if the damage is not too great, nerves can repair themselves, that the repair proceeds outward from the brain toward the periphery of the body, and that it happens at a rate of roughly 1 millimeter per day. So, he said, my problem would probably resolve itself but it would be a long time, think 6 months or a year, maybe even longer to finally be back to 100%.
And it basically happened just like he said it would. 6 months later, it was a lot better, and it continued to gradually improve from there.
He also mentioned that using the affected muscles would help encourage healing. I think he meant the nerve itself would heal faster this way, not just that it would help reverse muscle atrophy.
My layman's understanding is that a nerve is kind of a bundle of fibers wrapped in an outer layer. (Perhaps it's reasonable to compare it to a stranded wire inside an insulator, though I wouldn't say for sure.)
He said that if the outer layer is intact, the inner layer can be repaired. I'm not sure if that means more nerve fibers form or that existing nerve fibers are repaired but that the repair takes place incrementally instead of all at once. Intuitively it seems to make sense that a new fiber is growing, but I'm wary of speculating based on what seems to make sense to me.
Peripheral nerves are well known to regenerate, but the spinal nerves do not (or very limited).
We do not want nerves to regenerate in most cases because it could cause even worse results. If you start regrowing a batch of nerve, you have a chance of growing out nerves that transfer pain signals into places you don't want them to be, which could cause persistent neuropathic pain (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5290455/).
I cut a nerve at the base of my middle finger one time and completely lost feeling. Feeling came back over two or three weeks as the cut healed and eventually came back 100%.
Intact I read somewhere Cannabis consumption results in Neurogenesis. I am trying to find something for citation but unable to find anything backing this claim
Cannabis's Schedule I status makes it difficult for legitimate researchers to debunk (or confirm) the ever growing volume of nonsense cannabis proponents put forward to support legalization. Which ironically, is a pretty good argument for rescheduling it at least.
Same here, and it always seemed obvious to me that the brain was regenerating considering the nearly constant barrage of destructive shit thrown at it in adulthood without becoming vegetative; alcohol.
We're built to just last long enough to procreate because that's been the optimal way to keep our species alive. Regenerating causes issues (cancer, malformations, takes energy), so if the body can build it only once and last 20-30 years, it's optimal.
There was a talk in DEFCON about different substances that could stimulate neurogenisis and potential risks. The speaker mentioned the 1986 Nobel laureate Rita Levi-Montalcini who found NGF gave herself some dosage of NGF. The lady lived to 103 years old but the remarkable thing is that she is very productive in very old age. Later I found those peptids are extremly expinsive for normal people to consume
An absolutely amazing woman. She, a Jewish woman, carried out her preliminary NGF research in a shed whilst hiding from the Nazis in occupied Florence. She won the 1968 Nobel in Medicine due to the research she carried out in that shed. Though I am not 100% certain, I believe that she got her NGF via the only source possible at the time: cobra venom. So, imagine this scene: A 34 year old Itallian-Jewish woman Doctor is milking cobras in a shed in Florence while hiding from Nazis during the day, and at night she is a mob-doctor for the Italian anti-fascist resistance.
Do not ever let anyone tell you that you do not matter.
Do not ever let anyone tell you that you can't do something.
Are you joking or are you serious? How are you going to respond to a serious discussion with a flippant fact and not point us in the right direction? Care to share where eye drops are obtained? I'm so curious
He is not joking. The speaker mentioned in the talk. Peptides are not stable substance to be put into capsule. And the Bioavailability of NGF make it not effective even by injection let alone put pills in mouth. Nasal spray and sublingual are two other ways to absorb supplements but eye drop probably is the most effective one.
Since she lived 12 years longer than her twin sister I think the calculable effect would be the NGF supplement gave her around 13.18% more benefits with the assumption that her twin sister didn't take ANY supplement. The calculation is unscientific and might not be reliable though.
It's important to note that this is talking about normal brain neurogenesis. We have long known that external stimulus such as ECT, and chemicals such as 25i-nbome are neurogenic.
So are SSRI's. They promote neurogenesis in the hippocampus via BDNF. It's theorized as one of the reasons for the therapeutic effects of SSRIs that tend to only come about after ~2-6 weeks of use.
25i-nbome is a popular ligand for 5-ht2a activation due to its high potency (low amount required for action), stability, and iodine content (can be made radioactive without altering the structure). Someone probably had a thought about 5-ht2a stimulation leading to neurogenesis and tested it in mice using 25i because it's a good compound for that. Thus the headline "25i-nbome causes brain cell growth". (The psychedelic action of 5-ht2a ligands may have been a clue that they cause neurogenesis. Until tested it's only a guess.)
Yes. There is a doctor at the University of South Florida that was investigating it, and many LSD "micro-dosers" switched to using 25i-nbome even though it is very much a research chemical with no long-term safety profile.
However, psilocybin (the active component of magic mushrooms) is also a strong neurogenic compound, although not as effective as ECT. 25i-nbome is much stronger than ECT, even in tiny doses which are far below the threshold for any noticeable changes to perception.
I mean if that's what you call getting high now then go for it. You are completely discounting any damaging effects and the associated disconnect with reality.
In the human brain the hippocampus is actually 2 hippocampuses, one for each hemisphere. They are a little curled structures like two 'C' facing each other with the top of one nested in the hollow of the other. Where the end of one C nests inside the other there's a region called the dentate gyrus. In the dentate gyrus there are small granular cells. Beneath this layer are stem cell capable of becoming neurons.
Most of the activty of the dentate gyrus birthing new neurons is in during early development and when a baby. During these times there's a stream neurons from the sub-granular zone (beneath the granular cells in the dentate gyrus in the hippocampus). The perceptions of the external environment and the internal physiological state modulate the rate of survival of these new neurons.
It's kind of open in the sub-granular zone and the stem cells are able to move freely and assume multiple intermediate cell architectures before finally becoming dentate granule neurons that migrate to and integrate with the existing hippocampal circuitry along the other parts of the two nesting C shapes. They're even somewhat glia-like during part of this intermediate development. It's a complex process that's easy to interrupt. Most of the cells die and do not become integrated into the hippocampus.
So, to get to and restate the question: how do neuroactive chemicals and things like ECT potentially alter the rate of new sub-granular zone stem cells? If the current development state of the cell has receptors or the glia around it are effected by chemicals that bind to those receptors it's easy to see how things could be thrown off.
It is not necessarily a good thing to increase the rate of cell survival of new neurons in the adult. The rate of new neurons has important effects on the ability of the neuronal circuits in the rest of the hippocampus (involving CA1, CA3, etc) to do the types of memory encoding tasks researchers call pattern separation and pattern completion. So while there are indeed chemical and electrophysiological ways to increase the the survival rate of new neurons there should be reasons to believe the balance needed to be adjusted up.
Just as a throwaway, THC is one of the chemical compounds found to increase new dentate granual neuron survival and integration.
Fascinating! Do you have any sources for those interested in reading more about these theories of neuronal growth and the process of pattern separation/pattern completion in the Hippocampus?
1) It seems to mostly be focused on neurogenesis in the hippocampus, not necessarily elsewhere in the brain.
2) It seems the key item these researchers hit on to invalidate the previous study was the method of preservation for brain tissue in deceased individuals, not study of tissue in living humans. I think new studies in that latter area in the future will put the matter to rest.
Neurogenesis has always been about the hippocampus in humans. It's been lightly suggested it might happen in the olfactory bulb (as in other animals) but not very seriously. When neuroscientists talk about human neurogenesis in adulthood it is always about the hippocampal formation and the dentate gyrus.
For an up to date review/link-set of neurogenesis in humans as compared to other mammals check out the summary write-up over at http://blogs.discovermagazine.com/neuroskeptic/2019/01/30/ne... which makes the case that human neurogenesis isn't found in adulthood because of relative lifespan differences.
I’m experimenting with Piracetam and Noopept while learning coding. With a morning coffee I feel incredibly focused in ways I normally am not with caffeine alone.
I understand that many people need medications to help tune the brain back to more of a normal range, and it's great that meds are available to help them.
A general question I've been wondering about -- ever since it seemed half of some CS departments' undergrads were on meds, at the start of the dotcom bubble -- is what are the costs to discretionary use of meds as performance enhancers, by people who don't have abnormal brain situations to start with?
I'd like to know in general, and it might be important to public health or societal direction. But this doesn't seem the kind of thing that a non-researcher/doctor can ask individuals about, since it can be extremely personal.
My understanding is at worst they don’t do anything useful, which is why nootropics are sort of in a legal grey area in the US but generally legal in other countries.
I'd always consider that in situations like this "do not do anything harmful" is very different than "have not currently been proven to do anything harmful". In nearly all scenarios we're still very much in the latter case than the former. We're still discovering new negative consequences of things such as acetaminophen and aspirin which we've been consuming for, at least in the later case, literally thousands of years.
And you have to keep in mind with any sort of pharmaceutical there's a major bias in research. There's billions of dollars to be made by showing that things are effective and safe. There's much less of an incentive to to show that things are ineffective or unsafe. Even for those who are genuinely completely altruistically motivated, there's far more interesting research to pursue and topics that don't come with lovely consequences such as making influential enemies within the industry you're dependent upon grants for.
Consider things like cigarettes, leaded fuel, or whatever else. There's invariably decades of "science" proving it completely harmless before some crisis points triggers a 'reevaluation'. And for things intended to interact with your cognitive abilities, if there are negative effects it's entirely possible we might never reach that crisis point as any negatives effects may likely manifest in ways that are rather less apparent than the effects of e.g. lead or tobacco consumption.
Indeed, there’s all kinds of reasons to want to verify received products. I’d love to have a way to test supposedly organic foods for various pesticides. If there was a book on basic chemistry needed for this kind of thing I think I’d spend a season with it as a hobby.
Hi, I am on my third week of 30mg each morning, 7-8am is when I take it, never after 8am. I was diagnosed at 23 but didn't start until 26.
Sides during first week or so: increase in blood pressure, slightly higher heart rate, decreased appetite, teeth grinding, could feel a "crash" in late afternoon, some difficulty sleeping ~1030pm
After the second week: unsure about blood pressure, body has adjusted some and I believe it to be more normal now. Heart rate still increases slightly, appetite still suppressed throughout the day (I eat a banana early and try and get ~20g protein by noon), not getting those "Crashes" that i had first week (or if anything, not so bad), I can sleep now and I am aware of the teeth grind thing but that has definately decreased.
Overall I think body adjusted to this well, may consider 40mg instead of 30mg. Don't think i'll go over 40mg personally. The focus benefit throughout the day really helps me with my productivity
Oh I should note I kept drinking coffee during all of this. When I first started (with those sides) I went from 4 to 2 cups a day. Now I'm back at around 3ish cups a day.
Vyvanse is a legally controlled substance in the US, so there is plenty of information publicly available on the subject. The most common side effects off the top of my head are reduced appetite, increased blood pressure, and sleep problems.
I've been taking Vivance for years. FWIW, I had some of those side effects when I first started taking it and they have subsided for me. I still feel like I benefit from the medication and haven't ever felt like 'abusing' it.
So what age is considered "adult"? I've read other sources that say 26 or so, but they base that on the fact that it's when the brain stops growing. Forgive me if I missed something, but nowhere in the article do they define what adult means in this context.
> Forgive me if I missed something, but nowhere in the article do they define what adult means in this context.
The two alternative conclusions presented are skepticism of any new neurons in the target area after toddlerhood and the conclusion that neuron development seems to be lifelong, though reduced in and with the progress of Alzheimer's.
Well, fundamentally, neurogenesis is just another form of cell division. The most well known disease of cell overproliferation is cancer. Most brain cancers are of the glial cells (i.e. not neurons, but their support cells). There are some exceptions (e.g. some types of medulloblastomas).
A dear family member just started getting symptomatic with a progressive condition where their body generates new motor control neurons (or nerves? I'm not clear), which aren't connected to the brain. It basically amounts to line noise on the motor control circuit, producing incredibly irritating but otherwise harmless uncontrollable motion of specific downstream body parts.
Excessive neurogenesis from supplements almost always lead to things to like glioblastomas, or brain cancer more simply put. You should always be wary of anything related to increased growth or cell division.
Glioblastomas are generally the only really common type of brain cancer precisely because your neurons aren't proliferating in adulthood, which is very much a good thing.
That's why I mentioned you should always be wary of anything that purports to increase neurogenesis, as even if it does, that can lead to significantly increased probabilities of cancer development. And brain cancer specifically, is one of if not the most difficult types of cancer to treat, with extremely limited survival outlooks.
I've been seeing articles with this title far longer than I ever heard otherwise. Even if there are still people who think you can't regrow brain cells after more than two decades of science to the contrary, it's probably time we stopped saying things like "after all" as if neuroscientists just recently figured it out.
> Llorens-Martin said she began carefully collecting and preserving brain samples in 2010, when she realized that many brains stored in brain banks were not adequately preserved for this kind of research.
I was always curious about it, and this piece shed some light over it: as death is a process where all cells undergo chemical transformation, all you add to stop the process and preserve some state also induces changes. So, depending on how you preserve something, you will also lose information and won't be able to further study something.
Interesting how we have a long road regarding preservation of bodies and how much we still can improve about it.
It's not just that paper. There are many papers from many groups that have failed to detect neurogenesis in the dentate gyrus of adult humans. Even groups who's work is based on trying to find it have concluded it probably doesn't happen. They did not want that result.
The take-away for me seemed to be that methods of preservation and preparation were destroying these cells, leading to a situation where scientists suspected they didn't exist.
This seems to explain why that situation happened, nothing more.
No it's more the case that Alzheimers and dementia are caused by other processes which reduce or end this process. And a lot of the damage isn't necessarily caused by reduce neurogenesis but by other factors.
I don't believe so, I believe there's a whole different subject matter on that. As far as I've read up on Alzheimer's, it appears to happen when too much stress is incurred on the mind or nervous system. That's just from what I've been reading on HackerNews though. There's stuff on beta Amyloid, caffeine, herpes... The list goes on but the decrease or nerogenesis doesn't appear to be related. I'm no expert.
The case in point is the sciatic nerve is massive, and prone to constant stresses and strains, yet supposedly never regenerates.