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Why the brain’s connections to the body are crisscrossed
- Waterluvian 4y agoTangentially related to this is when I installed a patio in my yard two summers ago. Okay, let me explain: I had a sugar maple about 3 feet away from where I had to dig the foundation for the patio. An arborist said that it’s a bit close but the maple is strong and it should recover fine. I cut out a bunch of roots and within a month the exact sections of the canopy corresponding to the roots I cut went brown. It was incredible to me how the roots relate directly to the canopy. I always kinda thought it was one big circulatory system, where everything supports everything. I expected the whole tree to struggle a bit. Next season the tree was fully recovered. The neurological system seems to work the same way? It’s a directed graph where one root supports a very specific set of branches? I guess the circulatory system is like that too if you separate the two sets. Nature doesn’t really like cyclic graphs, does it?
- rolph 4y agoi think of it like a plinko ball setup, in analog. neural convergence, and divergence, produce logic arrays that integrate many parameters to one integrated decision, vice versa
- Waterluvian 4y agoIf your model includes a tiny Bob Barker commentating on the transmission of neural signals, I’m on board.
- PartiallyTyped 4y ago> Nature doesn’t really like cyclic graphs, does it? I had a course in computational neuroscience as part of my bachelor's and one of the things that we covered was that the timing of fires is important, in that depending on how soon before or after a neighbouring neuron fires, the connection may be weakened or strengthened. This is called Spike-timing-dependent plasticity: > Under the STDP process, if an input spike to a neuron tends, on average, to occur immediately before that neuron's output spike, then that particular input is made somewhat stronger. If an input spike tends, on average, to occur immediately after an output spike, then that particular input is made somewhat weaker hence: "spike-timing-dependent plasticity" From [1]. The implication of that, I believe, is that it prevents short cyclic graphs, for the sole reason of avoiding feedback loops that can cause the brain to go haywire (lol) due to the feedback loop. It sounds like an evolutionary adaptation to prevent short-circuiting. From Hebbian Learning, we have that the cycles would become easier to trigger, meaning that it is a feedback loop that increases efficiency, however, without a mechanism to prevent this cyclical feedback loop, the brain could be filled with cycles that eventually turn to just rings, which is probably not a desirable property. If anyone knows more about this please tell me. If it's a new idea, please remember to add my name :') [1] https://en.wikipedia.org/wiki/Spike-timing-dependent_plasticity https://en.wikipedia.org/wiki/Spike-timing-dependent_plastic...
- rolph 4y agojust keep inmind, this, and other phenomenon dont happen in all neurons, or in any particular neurons 100% of the time. neurons change functional, and structural state, depending on past events [hysterisis] and will shut down/modify state activities depending on feedback from post synapic neurons. also neurons will get tired and handoff activity to similar neurons in a cohort.
- domrally 4y agosome old classmates of mine published a paper related to feedback loops: https://www.frontiersin.org/articles/10.3389/fncom.2011.00028/full https://www.frontiersin.org/articles/10.3389/fncom.2011.0002...
- IIAOPSW 4y agoIts very much not a directed graph. We do have brain loops. That's where brain waves come from, circular paths of neurons activating themselves in a circular firing squad.
- ciconia 4y ago> I cut out a bunch of roots and within a month the exact sections of the canopy corresponding to the roots I cut went brown. Root systems in general (for trees at least) mirror what's happening above ground. Pruning trees is a beneficial intervention, as it causes the corresponding roots to die and decompose. This not only makes precious biomatter available for recycling by the microorganisms in the soil, but also releases chemical signals that cause the tree itself and neighbouring plants to send out new growth.
- derf_ 4y ago> I guess the circulatory system is like that too... I have some news for you: https://en.wikipedia.org/wiki/Circle_of_Willis https://en.wikipedia.org/wiki/Circle_of_Willis
- foobarbecue 4y agoWhen I worked for the park service, my botanist boss told me that the reason junipers and that sort of scrubby, stress-tolerant tree have twisty trunks is so that if they lose a section of roots they don't lose a sector of sunlight in the canopy. Because sunlight can be focused on one side of a tree (especially if growing on a steep slope), a twisting trunk can save a tree in the case of root damage on one side.
- deleted 4y ago[deleted]
- xwdv 4y agoWill you get different thoughts and ideas if you read a book with one eye closed vs the other?
- gibolt 4y agoThis is a mind blowing question. If so, does that mean your dominant eye is the default path?
- carapace 4y agoI do. Try it, YMMV. - - - - Normally when you look into your own eyes in a mirror they are each looking into themselves. If you cross your eyes and get the distance just right, you can look into each eye from the other. For me it causes a strange effect, or seems to. I would be interested to hear reports from others of their subjective experience of doing that? - - - - Edit to add: Reading aloud also has different effects than reading silently. I surmise that the extra feedback loop from voice to ear has something to do with it. A common proofreading trick is to read your writing aloud. You catch errors that are [negative hallucination?] elided by, uh, non-external loops.
- svnt 4y agoYour auditory memory is a different space than other forms of memory, so when you read aloud to yourself it permits you to buffer additional information and get to it later, in addition to mapping it through different perceptual space as you’ve noted. So at least the perceptual circuit and the time constraints are changed by doing so. I find that it no longer works very well for me though: I often read aloud without experiencing or remembering anything I’ve read at all. It’s the same autopilot that takes over driving.
- m3kw9 4y agoI think it evolved to be crisscrossed, likely non crisscrossed ones were just eliminated, I’m guessing for redundant reasons. Having it cross covers a bigger area and may serve to cover issues if part of the other side get severed.
- anonymouskimmer 4y ago> While there are lots of solutions to this wiring problem, the most elegant is to have two bilaterally symmetrical systems of wiring between the brain and the body, with the connections from each side of the body crossing the midline. Wouldn't a 3-D brain mapping also solve this issue? Do we just have this flipped symmetry because neural nets started out non-3-D in simple organisms, and we have all just inherited the 2-D structure as our brains have grown? Were there ever 1-D neural networks, and if so, how did they work?
- rolph 4y agothe problem is mirror image one, when mapping sensory field stimlus, to cortical field state. as far as 1-d networks are concerned, electrical excitation is not an absolute property of neurons. unicellular organisms employ variations of electrical potential to initiate, coordinate, and buffer functions, and future changes of state.
- anonymouskimmer 4y ago> the problem is mirror image one, when mapping sensory field stimlus, to cortical field state. For 3-D mapping onto 3-D I don't understand what you're saying. Except for vision, for which I understand there are optical properties that require image flipping and inversion.
- rolph 4y agolight bounces off objects and travels through the lens of the eye. when light exits the lens it is inverted, so things to your right are projected on the left side of the retina, the left retinae then communicate contralaterally to the right optical cortex. sensory field is the snapshot state of each neuron in a 2-d array. cortical field is same but it is now destined for processing. left and right fields differ by paralax and this difference is used, to construct a 3-d percept
- anonymouskimmer 4y ago
- bookofjoe 4y agohttps://news.ycombinator.com/item?id=35647341 https://news.ycombinator.com/item?id=35647341
- rhn_mk1 4y agoAs much as I like Quanta Magazine, they dropped the ball on this one. I didn't understand anything of the summary of the paper. I hope they attach some images to the next piece about topology...
- d--b 4y agoThis doesn’t explain why the left brain controls the right side of the body and vice versa, does it?
- rolph 4y agothis would be dependency of new structure, on founding structure, and methods. a plan is developed early,and departure from that initial architechture, is a scorched earth style revision, versus patching old proven fixes,on new hardware. its a tendency of biological systems to innovate one step at a time, as persistence is a demand, so the system is not overhauled large scale, that would be tantamount to major negative selection, thus non-persistent properties.
- makeitdouble 4y ago> The nervous system is cross-wired [...] I asked my doctor last week why this should be, all I got was a shrug. So I asked Catherine Carr, a neuroscientist at the University of Maryland, College Park. “No good answer,” she replied. After reading the piece, as he's proposition a potential theory based on mathematics and elegance of the solution, her reply still feels totally apt. That makes the title slightly misrepresent what he's trying to convey. We don't get the why, just a maybe. Otherwise I'm not sure 3d mapping simplicity is enough of an answer when the brain can also adapt to way more complicated configurations when receiving partial damage for instance. It also feels like we have very few organs that developped along the most simple solution
- kibwen 4y ago> Letters on your T-shirt appear reversed for the same reason that the name “Quanta” would appear flipped, as “Quanta” if you wrote it with your finger on a frosty window and then went outside to look at it. I'm amused at the audacity of the author for asking the webdevs to manually wire up a unique HTML span with a custom CSS transform solely to make a single word appear to be rendered as though seen in a mirror. :)
- pbhjpbhj 4y agoIt's the inline style is in a hidden div at the end of the story and within #postbody, I suspect the author did it -- it's part of the story content at least -- and so didn't need the webdevs to do anything different. It's a nice touch.
- deleted 4y ago[deleted]
- amelius 4y agoIf this is true, then perhaps we should wire motherboards in a way such that the connections are crisscrossed too.
- rolph 4y agothis may be effective, when the time comes to allow a synthetic, to have a mobile body, that must model its sensory input to a common format to parse against a stored data array, in order to decide what scheme to employ when negotiating a physical, 3+d world using 2-d arrays of neuromime excitation.
- khana 4y ago[dead]
- venk12 4y agoI understand that 2d brain to 3d brain connection requires an intersection (criss-cross) I drew that on a piece of paper. But I didn't really get why that has to be the case with 3D brain to 3D brain mapping. I am able to connect them without a need for an intersection. Are there easier examples to understand the intuition behind this hypothesis?
- N659 4y agoThere's a theory that says an ancestor of all vertebrates just flipped its head around and it stayed that way. (Source: https://arxiv.org/abs/1003.1872 https://arxiv.org/abs/1003.1872). Can someone who knows more about animal physiology explain this paper? Thanks.
- Shorel 4y agoBut that issue is related to the fact that insects have their nerves in the inferior part of their bodies, and the digestive tract on top, while we have our nerves in the back (protected by bones), and the digestive tract on the front, which would be the lower part if we were still walking with four limbs. The issue described here is left-right symmetry, and it also applies to insects, so it is more general.
- N659 4y agoSo far I have read that these are related theories and the "somatic twist" theory is an expansion on the earlier theory of inversion. And there seems to be another related but separate theory called the axial twist theory (explained in the linked paper).
- hackernewds 4y agoI think instead of inferior and top and back, It's easier to visualize as referring to them as anterior and posterior chain
- jiggawatts 4y agoThis should be the top comment here: a reference to an actually scientific analysis that uses an argument that is plausible from an evolutionary perspective. E.g.: someone else here was arguing that maybe the mirroring helps the brain keep processing inputs from the side that was hit. Evolution does not work this way! Flipping doesn’t “just” happen, that’s a huge morphological change. It had to have evolved incrementally, with each intermediate step having an immediate benefit. The paper explains how and why this may have occurred.
- 4y ago
- squillion 4y agoAfter an explanation that without L/R crossing the body map in the brain would be flipped upside down, comes this revealing passage: "To make sense of the sensation [...] your brain would have to switch from one somatotopic map to another one with the opposite z-axis orientation". This a textbook example of the "Cartesian theater" fallacy. It assumes a little person inside the brain who has to deal with an image projected upside-down. Of course that doesn't make sense.
- squillion 4y agoThe pictures with the finger at the end are even more confusing. They conflate the mapping from body parts to cerebral cortex (the cortical homunculus) with the mapping from the homunculus to some other part of the brain were the 3D environment is allegedly mapped. They don't make sense to me.
- refactor_master 4y agoSlightly related: there’s a YouTube video [1] of a guy teaching himself how to ride a bicycle “in reverse”, i.e. you turn left, and it goes right. It takes some practice but in the end it just “clicks”. So now he’s balancing and moving completely opposite to perception. So you’re right about the little man. I struggle to see why some arbitrary axis transform is “too hard”. [1] https://youtu.be/MFzDaBzBlL0 https://youtu.be/MFzDaBzBlL0
- KMag 4y agoI vaguely remember reading about some similar experiments with goggles that mirrored vision. As I remember, after a few days, people can mostly overcome the difficulties of having their vision reversed.
- Brusco_RF 4y agoI also have a vague memory of this but can't find any sources for it. I wonder if we're both hallucinating?
- hackernewds 4y ago
- gus_massa 4y agoI still don't buy it. Once you cut a person vertically in two half with a guillotine, you get two topological disks of skin. Each disk can be mapped into the 2D surface of the brain. It doesn't matter if the parts of the skin are in the same plane or rotated 90°. Obviously some parts of the skin are stretched, so a 2D map will cause a lot of deformation. Also some parts of the skin are more sensitive than other and will need more brain surface. But this is what is happening, there are a few maps in the brain https://en.wikipedia.org/wiki/Cortical_homunculus https://en.wikipedia.org/wiki/Cortical_homunculus and they are quite deformed, and they even have a few cuts here and there. Once you decide to cut the map in two parts, each part can be projected in both orientations without geometric problems.
- schiffern 4y agoMaybe related, maybe not, but I noticed this quote is incorrect: > Odd things happen when we [project 3D space onto a 2D surface]. On a 2D map, an airplane taking the most direct path between two cities appears to travel in an arc, and satellites orbiting the globe appear to oscillate in a sinusoidal path If you use the Gnomonic projection then all great circles become straight lines.[0] The only "catch" is that you need to cut the Earth into two hemispheres. [0] https://en.wikipedia.org/wiki/Gnomonic_projection https://en.wikipedia.org/wiki/Gnomonic_projection
- Jeff_Brown 4y agoThe hypothesis seems to be that processing across a discontinuity is costly.
- gus_massa 4y agoOnce you cut the person in two halves, it's easy to map the half to a plane. Imagine a sphere. You cut it in two halves, and you get something like this https://en.wikipedia.org/wiki/Nicolosi_globular_projection https://en.wikipedia.org/wiki/Nicolosi_globular_projection and use a scissor to cut it in the middle. Now imagine the initial sphere is made of rubber and it contracts to a body glove thigh around the person. There are no discontinuity inside each half. Just a huge discontinuity between the two halves, but each one is processed by a different side of the brain anyway. The projections in each half can be made in both orientations, the one that is like the skin and the mirror one. The non-mirrored is difficult to wire, but the mirrored one is easy to wire. About the discontinuity, there is a huge discontinuity between the two sides of your body that are processed by the two sides of your brain, and you don't notice it. Moreover, in each eye, there is a discontinuity because each half of each of your eyes is proceed in a different side of your brain https://www.quora.com/Which-side-of-the-brain-does-the-optic-nerve-connect-to-from-each-eye https://www.quora.com/Which-side-of-the-brain-does-the-optic... With that hardware I expect to see a black vertical line in the middle of my eyes, but the transition is quite smooth.
- renewiltord 4y agoFascinating. The magazine doesn't appear to have a way to pay to subscribe. Very interesting idea described here. I think it would benefit from some animations. I'm hoping that LLMs will be able to generate and animate SVGs to help with this.
- crazygringo 4y ago> Since Quanta is a nonprofit foundation-funded publication, all of its resources go toward producing responsible, freely accessible journalism that is meticulously researched, reported, edited, copy-edited and fact-checked. And our editorial independence ensures the impartiality of our science coverage — our articles do not reflect or represent the views of the Simons Foundation.
- canjobear 4y agoI don't find the TFA explanation convincing; it's too abstract. I like the explanation in terms of predator avoidance behavior. Imagine a primitive fish with eyes that can detect motion. If it sees something moving, usually it wants to get away from that thing. If you see something moving in your left eye, the best way to swim away is to send a signal for a muscle contraction in your right side, which will cause you to curl and swim to the right. So the best wiring is a direct connection from left eye to right side, and right eye to left side. The brain is built up starting from that kind of connection.
- ProjectArcturis 4y agoBut sensory input is also reversed. If you're touched on the right side of your body, it projects to the left side of your brain, which then projects back to the right side of your body again. If the goal were to minimize wire length, everything would stay on the right side.
- taneq 4y agoThis is my take. With two sensors connected crosswise to musculature that pushes forward, you get goal seeking for targets in front and avoidant behaviour for targets behind.
- kerkeslager 4y ago> With two sensors connected crosswise to musculature that pushes forward ...that's not what we have.
- taneq 4y agoIt's what our ancient ancestors had. And they were successful, and elaborated on that theme, and by the time they were complicated enough to start thinking "hey wait, why is our nervous system crossed up like this" it was too much bother to uncross it.
- kerkeslager 4y ago
- dghughes 4y agoThe recurrent laryngeal nerve too I'm not sure if it's all or most or some animals. It loops around the heart like a noob PC builder's first build and poor cable management. Giraffes have the best most extreme example of this.
- dandanua 4y agoIt's just for power balance, I think. Otherwise the left and right parts would be too independent. And this causes conflicts of interests.
- Acumen321 4y agoA theory I heard that I like, is that if you are getting attacked from the right, and suffer damage to the right side of your head, you probably want your right arm to work more than your left for the highest chance of fighting off the attack.
- Tagbert 4y agoIf your brain is hurt to that degree on either side, you are unlikely to be able to continue to fight. Evolution doesn’t usually work to offset unusual events like this. It is more about optimizing operations on a daily basis.
- deleted 4y ago[deleted]
- hackernewds 4y agoit should? natural selection progresses through the reproducers that survive. the ones that could attack on their right side for right side attack survived?
- aflag 4y agoSurvived with severe brain damage. Are they going to be able to survive for much longer to reproduce? It sounds that feature is only useful in a very specific circumstance. Evolution is usually happy with good enough. It seldom does micro optimisations like that
- Acumen321 4y agoBut maybe you get a few more seconds, one more swing, and take out your opponent. Your tribe kills the lion or wins the war. If the initial mutation wasn't detrimental so wasn't tested right away on an individual basis, but allowed to reproduced to form a population, it would be the group test that gets passed. Just a thought.
- killdevil 4y agoI have always assumed that bilaterally symmetric animals have neural cross-wiring so that the two hemispheres of the brain are forced to cooperate more than they otherwise would. Simple animals are prevented from, say, hoarding resources selfishly and maladaptively on the right.
- nnlsoccer 4y agoOdd that in the entire explanation they completely ignore embryology and the pathway dependence that came with evolutionary progression between species
- oncotic 4y agoI disagree with the author's interpretation of this. As a neurologist myself, I was taught it was specifically to simplify visual processing, although there may be other theories but this is what I was taught. Like others commenting here, the way the lens works in each eye is by flipping the image onto your retina. If we had only one eye, there would be no issue, the image would appear as a continuous image, just flipped around. However, because we have two eyes, they both individually flip different fields, thus separating the continuity of the image horizontally. If you try drawing out various different ways to try and remedy this problem of binocular vision, the way nature's approach is quite elegant in reuniting the image as well as separating visual processing into left/right. To avoid a large text explanation, this is a simple diagram of the concept how the brain reforms the arrow. https://nba.uth.tmc.edu/neuroscience/s2/images/html5/s2_15_14.jpg https://nba.uth.tmc.edu/neuroscience/s2/images/html5/s2_15_1... The way it works is by separating the left and right fields of each eye, and then crossing them so that the left fields goes to the right half of the brain and the right fields go to the left half of the brain. Each right/left half is now interpreted by one side of the brain and the image is again continuous if you draw it out on the brain. Of course now each side of the brain sees the opposite side, but we remedy this by crossing everything else so it plays well with visual interpretation. Now the right side of the brain sees, senses, and controls the left side of the body and vice versa. When it comes to everything else, there isn't a clear benefit for having processing swapped to opposite hemispheres. But visual processing benefits from it greatly, and so the rest of the nervous system goes along with it.
- punnerud 4y agoJust the swapping of sides in the brain, isn’t there a clear benefit for the stress/weight of the nerves to the rest of the body? If right side was connected right arm the nerves would be pressed “out”. When they cross there is less pressure in the spinal cord?
- elcritch 4y agoFlipping the eyes is the same geometric reasoning the article discusses. The same thing applies to touch and motor control too. Its just a general extrapolation of the same principle. It would also explain why creatures without sight as well like many worms.
- everyone 4y agoI once read that an ancestor of ours evolved to have its head rotated 90' relative to its body (like a flatfish or something), but then later when it evolved a normally aligned head again, instead of twisting back 90' the way it had come it just twisted another 90'degrees
- spicyramen_ 4y ago[dead]
- mensetmanusman 4y agoWhat is the purpose of trying to add reasoning behind how we were created?
- ramblenode 4y agoI'm surprised the article and comments haven't mentioned the axial twist hypothesis [0], which IMO is the best explanation I've seen so far for contralateral wiring. The axial twist hypothesis has experimental evidence and is also predicted from physical first principles of what is known about embryonic development. It explains the central decussation, which is a stronger prediction than the existence of some decussation (from what I understand of the article). I still don't quite understand how one gets from the existence of a decussation between two distinct body-cortex paths to contralateral organization, but maybe after reading the paper I will get it. That said, wonderful and simple result. [0] https://en.wikipedia.org/wiki/Contralateral_brain#Twist_theories https://en.wikipedia.org/wiki/Contralateral_brain#Twist_theo...
- iamnotsure 4y agoMy theory, this is not about crisscrossing but about splitting. Splitting is done to avoid shared state. Non shared state is crucial for individuality. Other senses - hearing, touch, smell are wired in the same splitting way - hearing from the left ear is processed in both brain hemispheres, so is hearing from the right ear. Now the problems with digital photos is that they are the very thing the brain wiring avoids - a single non-split capture, this is the cause of confusion on a mass scale. This is gravely amplified by recent advances in "AI" object renderings. Brain or unconscious has no tags to differentiate between real and artificial. I have multiple experiences of software systems displaying artificial splitting and duplication, I also experienced duplication of objects in the real world. If anyone knows anything about such experiences or can correct errors in this comment or provide further clearer explanation, please do. I believe some quantum phenomena can be at play here too. I also experienced double stereo hearing, my hearing was as if I heard two separate stereo inputs, as if I had four ears. I have aphantasia, if that matters.
- eru 4y ago> [...], I also experienced duplication of objects in the real world. [...] I believe some quantum phenomena can be at play here too. Almost certainly not. Don't take this the wrong way, but you might want to get your brain checked out..
- iamnotsure 4y agoNot that I fully disagree, but this reply is of limited helpfulness. I don't think quantum phenomena can be ignored within the context of human body. I don't know what happens with double-slit experiments, how the sight of it is encoded in the body memory. Software developers have great tools for assuring and checking source code correctness, but the situation for meat-space bodies is very different in practice. Unless you live in some advanced techno-utopia with access to advanced medicine. I don't know where to look for help. I can't run fsck-brain /dev/brain on me.
- eru 4y agoFrom the point of view of quantum mechanics your body is very 'noisy'. You only see quantum mechanical effects, like what you see in the double-slit experiment, in essentially undisturbed systems. That's why when you 'measure' which path the photons take, the interference pattern in the double-slit experiment fails to occur. Your body having lots and lots of atoms sloshing around at body temperature is analogues to taking measurements. It 'collapses' the wave function, if you pardon me using terminology from the Copenhagen interpretation. See https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=919863 https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=91986... for some background. Or perhaps https://en.wikipedia.org/wiki/Quantum_decoherence https://en.wikipedia.org/wiki/Quantum_decoherence first as an introduction. As an aside: (thermal) noise demolishing quantum effects is a big part of why it's so hard to actually build a quantum computer. What you described might be hallucinations, and so you might want to go to a neurologist or so.
- femto 4y agoIt reminds me of the routing for an integrated circuit to do a Fast Fourier Transform. The butterfly operation on which an FFT is based involves a crossover, so the basic problem in routing a planar chip is how to make all those crossed over connections. It would be pretty cool if the brain was doing an FFT!
- TeeWEE 4y agoThe real reason is much simpler: first step in evolution is 1 ligt sensor connected with 1 muscle. If the eyes sees danger you need to swim away from it. If you see food you need to swim towards it. Food was initially abundant l. Do moving your right muscle would cause you to move toward the food. Later it evolved to be the brain
- moremetadata 4y agoAs someone with a high signal lesion in the genu of the corpus callosum caused by childhood head injuries I think the brain split in two halfs is simply an impact "kill switch" for severe adult head injuries. Ergo extreme impact trauma to the head results in the brain breaking the connections between the two hemispheres at the corpus callusom, resulting in immobolisation. However this could also be a temporary kill switch which immobolises the body until such time as the brain's neuroplasticity has restored the corpus callosum. In such a condition the individual would likely be left for dead, be going hungry and quite likely thirsty which creates an increase in phagocytosis which in turn causes an increase in h2o2 and then catalase the enzyme from the liver breaks this down to water and oxygen, ergo the conditions to help the body live, if not in a slimmed down form (pun intended) still exists and lends credence to fasting.
- IYasha 4y agoBecause no auto MDI/MDIX, right? (posted before reading :) )
- seydor 4y agoThat is certainly a hypothesis Auditory signals don't cross. We should raise a human with eye flipping lenses
- Jeff_Brown 4y agoWhy is the brain's representation of the 3d world 2d? Wouldn't it be more natural to map the infinity of space, body included, onto a (topologically open) ball in the brain?
- astral303 4y agoMy guess is that this enables crosstalk between the nerves which would have been entirely absent otherwise. And crosstalk between left and right sides of the brain is beneficial evolutionarily.
- psychphysic 4y agoNo mention of the fact the crossing over happens at different levels if at all in the body. Look up Brown-Séquard syndrome for a House MD level quirk of the body.