[HN Gopher] A neural code for time and space in the human brain ...
___________________________________________________________________
A neural code for time and space in the human brain [pdf]
Author : bookofjoe
Score : 113 points
Date : 2024-03-10 16:36 UTC (1 days ago)
(HTM) web link (www.cell.com)
(TXT) w3m dump (www.cell.com)
| itsthecourier wrote:
| So they found the probable place where neurons dealing spatial
| and temporary matters are located?
| echelon wrote:
| > Our study reveals neurons in the MTL and mPFC that encode
| time and space during exploration in a virtual environment for
| fixed durations. Time cells activated at rest in the absence of
| movement or other external contextual change, while distinct
| time cells and place cells emerged during navigation and ex-
| hibited divergent responses to changing tasks. These results
| demonstrate a neuron-level code for spatiotemporal context in
| the human brain, in which time and space are simultaneously
| represented but not wholly conjoined.
|
| Hack for skimming papers:
|
| 1. Read the abstract. It's short and will tell you what the
| paper investigates. If it's too much jargon, skip it and come
| back.
|
| 2. Skip the entire paper and read the "discussion" or
| "conclusion" near the end. This will pretty much tell you what
| the paper is saying, typically in more familiar language.
|
| 3. Go back and re-read the abstract.
|
| 4. If you're still interested, read the figures.
|
| 5. If this paper is up your alley, now you can read the whole
| paper with context and can appreciate the methods of
| investigation.
| neuronerdgirl wrote:
| One small suggested addendum: 1.5) read the last paragraph or
| two of the intro. Most good papers spend these paragraphs
| laying out their study and their expected and alternate
| hypotheses. It's a quick way to go from the floaty higher
| order topics covered in the abstract and discussion and drill
| into exactly what the scope of the paper actually is.
| coffeebeqn wrote:
| Next step: psychedelics that hit that area
| Aeglaecia wrote:
| Dredd (2013)
| kensai wrote:
| Formidable work. But as always, let's wait until it's confirmed
| from other groups. I wonder if AI was fed with advancements in
| understanding of neural code: would that speed up the coming
| Singularity?
| jegp wrote:
| Is this novel? Spatial codes have been known for long and neuron
| (populations) are known to code for time [1]. That reference also
| states that "Neurons that respond selectively to the temporal and
| spatio-temporal structure of sensory stimuli have also been
| identified in the auditory system of birds and mammals". Doesn't
| that pre-empt the conclusion that "Thus, the brain can represent
| time and space as overlapping but dissociable dimensions".
|
| [1]:
| https://royalsocietypublishing.org/doi/10.1098/rstb.2012.046...
| neuronerdgirl wrote:
| It does not, just that both dimensions are coded for in some
| way. Per the current article, temporal and spatial codes have
| been previously studied in isolation, so it was not known if or
| how they might be intertwined. This has elucidated new nuances
| of that relationship.
| godelski wrote:
| > Is this novel?
|
| Novelty is not a good question to ask. It is meaningless.
|
| Instead ask:
|
| - Is it plagiarized? Or is it redundant information organized
| in a way that does not benefit others?
|
| - Does it provide utility to __someone__ in the research
| community?
|
| - Is it void of any major mistakes?
|
| Novelty is just an absurd idea that is *destructive* to
| scientific progress. If you abstract ideas, nearly every idea
| is just <x idea, abstracted> + <y idea, abstracted>. Generally,
| science moves forward in small steps. You DO NOT want to
| criticize work on novelty because you actively encourage
| obscurification. This happens, a lot, and not just by small
| teams[0]. Unless you are intimately familiar with the specific
| sub-niche, you probably can't accurately judge novelty because
| the small steps and the nature of expertise is literally
| predicated on having an extremely nuanced understanding of a
| topic. So you're going to abstract and cause the aforementioned
| error if not careful.
|
| In fact, a well written paper will often trick you into
| thinking that you already knew all this beforehand. This is
| even codified in the Socratic method. So many new things that
| change the world often leave us thinking "well that was
| obvious." Maybe it was, maybe it is only obvious in hindsight.
| Either way, it was useful. Either way, you didn't do it, and
| someone has to.
|
| As far as your reference vs the one here, at least to me they
| seem quite distinguishable from the abstract alone. From
| further reading, I'm not sure how you conflate these other than
| they are studying the same topic. For one, your work (which was
| 10 years ago btw) isn't working on mammals while the current
| one studies rats. The new one looks much more detailed, has
| more complex task and convincing experiment, and honestly, is
| far more reproducible. I am curious why you think these ideas
| are identical or so similar that no new knowledge is gained.
| This is an honest ask. I do want to understand[1]
|
| I think we need to ask ourselves what we want from science. For
| me, that is: reproducibility, communication (the clearer the
| better), and exploration of the unknown (exciting or mundane).
| Personally I don't care about utility, but that's because the
| abstract comment above and I've seen history to show this
| purist it naive at best and egotistical at worst (thinking I
| know so well). (I can list entire fields if need be. I'll give
| you a start: knot theory) I actually want explicitly non-novel
| works to be, frankly, common! Trust, but verify. We did not
| trust the LK-99 authors and move on, we verified. Even with
| failure to replicate, we still learned a lot. Don't forget that
| part! I'm perfectly fine if we have "too many" papers, as
| there's already more than any one can read today (look at ML if
| you want. It hasn't died, it accelerated when everyone started
| pushing preprints (and boy do most of those not get published,
| many for this exact reason. I've had to defend great papers
| written by rock stars because self proclaimed novices thought
| the work was not novel enough, including in workshops...). I
| don't want a focus on utility because we shouldn't railroad
| research paths. This is often even incompatible with the
| concept of "novelty"! I'm happy to let researchers explore
| "dumb" ideas because if it works it works and if it doesn't I'd
| rather them write it down and let others know.
|
| We need to SERIOUSLY consider the incentives of research,
| because I for one think they are not aligned with the goals.
|
| I'm upvoting your comment not because I agree, but because it
| is an all too common sentiment I see, and I believe it is
| ruining science. The worst of Goodhart's Law: Goodhart's Hell.
| But you are welcome to disagree and I am happy to learn and
| understand the positions of others. I'm just in my little
| bubble trying to learn about other little bubbles.
|
| [0] https://www.youtube.com/watch?v=Pl8BET_K1mc&t=2526s
|
| [1] https://news.ycombinator.com/item?id=39648459
| haswell wrote:
| The construct of time feels so _real_. And the fact that we
| surround ourselves with clocks, learn how to tell time from an
| early age, and live our lives aligned to precise schedules just
| reinforces this feeling of realness, and reifies the illusion.
| Seems like we are in a very literal sense time keeping (or
| "creating" might be a better word) machines.
|
| At some point I got fascinated by flow experiences and the loss
| of all sense of time. While I've experienced this while coding,
| improvising music has always been the gateway that fascinated me
| most. No time to keep; no measures to count; nothing but the next
| note. There's something about staying continuously in contact
| with the present moment that makes the time construct just
| dissolve.
|
| And all that's left is this continuously unfolding moment. No
| time. Just now.
|
| I remember hearing things when I was younger like "time is a
| construct" and not knowing wtf people meant. Flow states helped
| the conceptual vs. experiential versions of time make more sense,
| and it's pretty fascinating to see more about the neurological
| basis for the experience of time. It seems to just underscore the
| fact that time (as we think we know it) is an experience our
| brain creates for us. Clearly there's some underlying phenomena
| that these neurons are representing, but it blows my mind a
| little to ponder how much we orient our understanding of life and
| experience around the constructs we've created vs. exploring
| other ways to conceptualize and experience it.
| tomcam wrote:
| Wait how do you improvise music without counting measures? Or
| are you strictly solo and/or freeform?
| haswell wrote:
| Solo and freeform on a piano.
| discreteevent wrote:
| It's also possible that time is real. One thing happens
| after/causes another. It's possible that when you are in a flow
| state your brain is just failing to notice the time that is
| objectively passing in the world around you.
| haswell wrote:
| I don't question that something is happening that we
| experience as time. But the point was that the ways we
| commonly experience it tend to instill ideas about what it is
| that seem not very close to whatever is objectively
| happening.
|
| I think the point about the flow state is that it's one of
| the most reliable ways to disconnect from that common
| experience, and doing so regularly starts to reduce the
| primacy of the constructs we've built on top of it.
|
| Another way to put this is that the common clock and schedule
| oriented notion of time is just a complex set of concepts and
| labels and increasingly granular slicing of ongoing
| experience into chunks we can use to reason more effectively
| about other aspects of experience.
|
| It's extremely _useful_ to be able to make plans with a
| friend at 3PM next Thursday. 3PM next Thursday doesn't exist.
|
| Understanding the rate at which phenomena occur helps us
| develop increasingly useful and accurate world models. To
| understand what "rate" even means, it's necessary to build up
| some concept of time.
|
| What I'm mostly pushing against is the primacy of that
| construct. The pervasiveness of clocks and schedules to a
| point that it feels like they rule us. The past and the
| future tend to feel like places that exist. Time tends to
| feel like some kind of arrow. We're always coming from some
| point in the past or going to some point in the future. A
| useful tool to help us make sense of our memories, and decide
| what to do next.
|
| But the role of time in what actually happens at any given
| moment seems pretty unlike our experience of it, which seems
| to be something we largely manufacture to make sense of the
| rest of human experience.
| tobiasSoftware wrote:
| One of the weirdest things Einstein discovered is that time
| is relative, but cause and effect are absolute.
|
| For example, muons should decay before they hit the ground,
| but they don't due to time dilation. We see the time dilation
| when observing the muons, but the muons don't, so you would
| think that for us, the muons make it to the ground but for
| the muon it would decay too fast. However, the muons
| experience length contraction, so they do make it to the
| ground from their viewpoint as well.
|
| So cause and effect is preserved, even though we would
| disagree with the muon on the relativistic reason why it is
| preserved.
| drdeca wrote:
| Time is relative, sure, but "proper time" isn't relative.
| syspec wrote:
| > For example, muons should decay before they hit the
| ground, but they don't due to time dilation.
|
| Would you mind expanding on this?
| thomastjeffery wrote:
| Time is a dimension of space. We are falling through time
| just like the other 3. The only way to know you are falling
| is to see something that isn't. The tick of a clock draws a
| boundary in time just like a pen draws a line on a page.
| bugbuddy wrote:
| Usually the comment sections here are pretty fun to read but
| anything neuroscience related results in absolute cringe-inducing
| comment chains. This one is no exception.
| parpfish wrote:
| The vibe I usually get for HN neuro stuff is "The brain is just
| a computer and we know how those work, so what's the big deal"
| neuronerdgirl wrote:
| HN has a lot of people who are quite smart but have not been
| through graduate school or academia, so they don't realize
| just how niche the type of training and topic-specific
| knowledge you get in that world is relative to a classic
| university-to-industry track. I think that is true for the
| general populace too - it takes doing the depth of learning
| and research you have to do for a PhD to realize _just how
| much_ there is to be known about even the narrowest slice of
| a topic even relative to the most intense casual enthusiasts.
| I suspect this is a major reason for the high levels of
| impostor syndrome seen in academia, but that is a tangent.
|
| Neuroscience is also a field that mostly happens within
| academia, unlike something like computer science where a ton
| of work legitimately is being done at the types of companies
| many HN users work at, so where you can indeed get something
| approaching expert-level knowledge on the job in some cases
| in the latter, almost no one on the forum has enough exposure
| to be an expert in the former. Couple that with the previous
| thesis and you end up with a bunch of people who don't know
| what they don't know (I will not be engaging on Dunning
| Kruger in this thread). That plus, perhaps, a bit of hubris
| and you're gonna get a wonky comment section.
| godelski wrote:
| I think the brain is a computer.
|
| But I don't know how "computers" work nor do I know how
| brains work. (I do know a fair bit about the types of
| computers we are talking to one another and that host HN, but
| a computing machine is more than that) In fact, that's what
| got me into ML in the first place. What a crazy computer,
| that we've been studying it for thousands of years but still
| so much remains a mystery. How even extremely basic questions
| have baffled us for centuries. We still stumble over the
| nature of consciousness, sentience, and sapience. We still
| can't even agree on the definitions of these things!
|
| And by computer, I mean that there is a mechanistic process.
| One that is void of magic and beholden to the laws of
| physics. Which means, we should be able to replicate it. But
| this is also true for planets, galaxies, and so much more. So
| that does not mean it is within our capacity now or anywhere
| in the near future.
| ramraj07 wrote:
| Can anyone in this rough field even comment on the long term
| benefits of such research? And why this needs to be in Cell? I've
| tried my best to attend as many neuroscience talks about work
| like this regarding place cells etc and keep walking out of them
| scratching my head what the point is in the long term.
| homeless_engi wrote:
| Not an expert, but one application of neural decoding you may
| be aware of is brain machine interfaces (eg Neuralink). By
| decoding motor intent we can create devices which offer
| movement to paraplegic individuals with external robotics.
| Decoding neuronal activity in other parts of the brain could
| allow us to directly interface with other neural functions.
| Imagine a machine that could interpret your perception of space
| or time (or even modify it).
|
| Another application is in computing. Advances in the
| understanding of neuroscience have stimulated the creation of
| artificial neural networks (for example, the convolutional
| neural network was inspired by the cat visual cortex).
| Understanding how the human brain encodes concepts such as time
| or space might help us to design artificial systems.
|
| Finally, the most important aspect of this work is (imo)
| advancing basic science. We don't understand how the brain
| works, and work such as this brings us closer to solving the
| grand mystery of neuroscience.
| neuronerdgirl wrote:
| You can't see the point of elucidating the nuances of the way
| the brain encodes the information around us? Surely even if you
| see no value in basic science of this nature in and of itself
| (in my opinion a mistake) there are myriad application-based
| reasons to understand how the brain works, including both
| medical progress and the brain's influence on artificial
| intelligence designs.
| ramraj07 wrote:
| To clarify, I did my PhD in an immunology department in a top
| US grad school, and I attended the talks by the actual
| authors of some of these seminal works in the neuroscience
| department next door. My question was not an indictment on
| all basic neuroscience but a request for clarification on how
| this particular mode of questioning (pointing out that there
| are grid cells or time and place cells) is productive in us
| figuring out our brains.
| a-dub wrote:
| it's basic science. you know what and why that is.
|
| and thanks for reminding me! i've been meaning to pick katalin
| kariko's book back up!
| andbberger wrote:
| the long term point is to understand how the brain works. hope
| that helps.
| qnleigh wrote:
| Grid cells and place cells are among the very few examples
| where we actually know what a population of neurons is doing.
| This is exciting for at least two reasons:
|
| 1. If we know what the neurons do, we can start trying to
| understand how they do it. Like at the circuit level. And if we
| can figure that out, this will very likely help us figure out
| what other neurons are doing and how their circuits work.
| Currently very little is understood.
|
| 2. There's a lot of speculation that grid cells are also used
| for higher-level cognition, to represent relations between more
| abstract things. This is one of the two main theses of '1000
| Brains' by neuroscientist Jeff Hawkins.
|
| Why are these two things interesting? Well wouldn't it be cool
| to understand how the brain works? It might help us build AI
| that learns as fast as we do (chat GPT was trained on more text
| than one could read in many lifetimes). It might help us
| augment our own intelligence. These are very long-term goals of
| course, but understanding grid and place cells seems like a
| reasonable starting point.
| falcor84 wrote:
| The temporal lobe got its name because of its proximity to the
| temples, so it would be incredibly serendipitous/prophetic if it
| turns out to actually encode temporal information.
| kian wrote:
| Were temples not themselves often used to encode
| [spatio-]temporal information (about the time of the year, our
| location within the solar system and cosmos, etc) within their
| construction, now that you mention it?
| JohnMakin wrote:
| I had a rare condition in 2022 that caused me to lose track of
| all sense of sequential memories, which heavily affected my
| perception of time. I could not reliably tell anyone if something
| had happened 2 years or 2 weeks or 2 days ago or what order
| events had taken place without using significant deduction. It
| was incredibly distressful and confusing, and I had to rely on
| copious note taking to get by day-to-day. When my sequential
| memory returned, I have never ever felt more appreciation for
| this sense.
___________________________________________________________________
(page generated 2024-03-11 23:02 UTC)