
MIT discovers the location of memories: Individual neurons - mrsebastian
http://www.extremetech.com/extreme/123485-mit-discovers-the-location-of-memories-individual-neurons
======
mechanical_fish
OMG, it's the ultimate mechanical_fish pet peeve collection! TL;DR: I rant.

ONE: I can't find the citation of the scientific paper on ExtremeTech. (Let
alone a link. Who would dare to dream of a link?) They do refer obliquely to
"the paper" once. (What paper?)

And they link to MIT's press office, whose brand is really solid, so
everything they write is almost like science! And there you can skim the
article twice and finally spot the citation:

 _Susumu Tonegawa, the Picower Professor of Biology and Neuroscience at MIT
and lead author of the study reported online today in the journal Nature._

Okay, gotta go find an online _Nature_ subscription to find out what's going
on. There's an hour of my day spoken for. At least they're trying to ensure I
get some exercise.

Why is the actual journal article important? Just look at this thread here on
HN. We have people doubting all sorts of things, but these may well be things
that are addressed in the _actual work_. The content of the popular articles
means very little: They leave out most of the details. The details matter. The
whole _point_ of this study is to try and tease out more details.)

TWO: But, wait, there's more. I first tried to read ExtremeTech on an iPad
(original edition). The article popped up in one of those insufferable iPad-
only JS-powered "mobile editions" with Swiping Action. Unfortunately, there
was only the first page of the article. It cut off in midsentence. I tried
pressing the giant button marked "Next" on the right side of the screen. I got
a big white screen. I flailed around with my fingers. A _completely different
article_ eventually rendered itself. I flailed around with my fingers some
more. Eventually the original article reappeared, still incomplete.
Fortunately, one more roundtrip to the next article and back and I finally got
the whole thing to render.

Then I pressed the back button and everything seemed to hang. I closed the
browser window and thanked the gods for my escape.

Why on earth do publications use these broken things, when simple web pages
render so nicely on the iPad? The site does have something like a dozen
tracking cookies on it; does this imply that they have data showing that
swipability is so important that it _doesn't even have to work_ in order to
attract more ad impressions/clicks/Tweets/whatever? Or does it merely suggest
that they are so busy struggling with glass-cockpit syndrome that they can't
perceive that their site is broken on the iPad?

~~~
mrsebastian
I will add a link to the paper itself; sorry about making you jump through
hoops.

~~~
polyfractal
Hey, props for responding to criticism! As a (now ex-)neurobiologist, it's
maddening when journalists don't cite the paper they talk about. I helped
start ResearchBlogging.org way back in the day to help fight this very
problem.

If I may make a suggestion: wrap your citations in OpenURL COinS format.
ResearchBlogging.org provides this functionality automatically, but you can do
it yourself too. It provides a lot of useful meta-data, citation information
and the ability for plugins to interact intelligently with the web-page

[1]<http://ocoins.info/>

~~~
mrsebastian
Is this similar to the DOI thing? I have been thinking about doing that, too.

~~~
polyfractal
It's related. DOI is basically a universal identifier that acts as a "domain
name" for academic literature. This is to prevent broken links over time.

The big providers (Elsevier, etc) are obligated to maintain the DOI no matter
what happens on their end. E.g they may completely change their site
architecture, or change domain name, but as long as they keep the DOI updated
with the current location of the paper nothing goes wrong. DOI's all around
the internet will still continue to point at the paper.

It's a lot more robust than directly linking to the paper itself.

COINS is a way to embed bibliographic meta-data into a webpage. There are a
number of plugins/extensions that will grab this metadata and do useful
things. One example is an extension which automatically redirects links
through your library's link resolver so you get the paper and not the paywall
page.

------
jules
The data doesn't warrant the title of this post. Even if a single neuron is
responsible for triggering a memory (which is hard to say based on mice in the
first place), it doesn't follow that the information is stored in the neuron.
As an analogy, if we erase a specific bit in memory, whole parts can become
unreadable. For example imagine changing a bit in a pointer. That doesn't mean
that all of the information was stored in that bit.

~~~
amalag
I agree with this. Because of the brain's ability to access things which are
not exactly constrained to it's physicality, I think the brain acts as a type
of radio and tunes into memories. Not exactly sure how they are stored.

~~~
mrsebastian
There's a very strong urge to believe that the brain "tunes" into some kind of
non-meatspace realm (spiritual, quantum, etc.)

Fairly sure that it'll turn out that it just depends on the massive complexity
of neuron/synapse connections, though.

But then you think of concepts like 'group psyche', and twins that are
separated from birth but share the same thoughts/feelings over a distance...

Hopefully science will get to the bottom of it soon :)

~~~
dromidas
The twins thing is easily explainable by a programming reference. Seed 2
instances of the same random generator class with the same seed and have them
run a million numbers on different computers... the millionth number will
always be the same. Humans are just big wet sloppy computers with a little
more noise than our PCs (environment is different for everyone, even identical
twins are not in the exact same space) so it's likely that twins will more
often than anyone else be thinking in parallel with each other from time to
time.

------
bigiain
I can't help but think that what they've discovered is some meatspace
equivalent to the hash key or an index key to a memory. By "turning it on or
off" you can lose or find a whole table row or hash value, but surely a
"single neuron" can't "store" a generalised "memory".

~~~
snippyhollow
A neuron "could" store a generalized memory (the amount of information it
stores is gigantic, w/o pendantically considered the DNA). However, it's more
complex than that (there are many types of memories and many means of
retrieval). Basically, memories are sets of synaptic connections, and a neuron
has many synapses (average ~7,000 synaptic connections/neuron to multiply by
our 10^11 neurons/brain). As you said, it may be a "key", but it should be
seen more like the memory _is_ a complete list of hashes. Not {"key": memory}
but {"key1": {"key2": {"key3": {...} } }, {...}, {...}, ...} and the set of
{key1..keyN} is the memory. So if you removed whichever keyI in the middle,
you lose the information. (That's not really true because there is high
redundancy, but there are keys/synapses/nodes less redundant than others. The
fact is, they don't fire on only "one" neuron, they fire at a very precise
region but the light still goes through a population of neurons.)

~~~
bigiain
Fascinating, thanks! Have you got some links or keyphrases I should feed
Google or Wikipedia to learn more (at a "curious but not neuro-science trained
dilettante" level of understanding)?

~~~
snippyhollow
I'm in this lab <http://www.lppa.college-de-france.fr> and mostly learned
through colleagues (I'm doing CS/AI/ML, not neuroscience). I've read some
parts of "Neuroscience 3rd edition, Purves et al., Sinauer Eds." which has
nice pictures but I think there are better books and better advices than mines
on this. Perhaps start with Wikipedia,
<https://en.wikipedia.org/wiki/Hippocampus> //
<https://en.wikipedia.org/wiki/Memory_consolidation>

~~~
bigiain
Thanks again! stuck in the reading queue for the weekend. (Phear my curiosity,
people waiting for a table in my café!)

------
seclorum
They didn't 'discover the location of memories', they simply discovered that
they can trigger a reaction that looks similar to that of the original
incident by focusing energy on parts of a mouse brain that were actively
stimulated during the incident.

This is Pavlovs dog with optics, not revolutionary science.

~~~
GiraffeNecktie
I don't understand your reference to Pavlov's dog, it's more comparable to
Penfield's work with stimulation of specific points of the brain. Also the
ExtremeTech headline is a bit misleading. The related MIT article is a little
more clear that this involves memories in a small cluster of neurons, not one
memory per neuron as is implied by the heading above.
[http://www.mit.edu/newsoffice/2012/conjuring-memories-
artifi...](http://www.mit.edu/newsoffice/2012/conjuring-memories-
artificially-0322.html)

~~~
mrsebastian
Yea -- sorry, I mention later that it's a cluster, but I will update the first
paragraph to mention that it's a cluster, not single neurons.

------
hippich
I always was under impression that there are no memories as we think about
photographs, but rather state of the brain is one whole memory system, which
react to external signals accordingly to previously "memorized" signals.

As I understand, that they just found a way to excite particular small part of
the brain which triggered reaction without external signaling. I.e. bypassing
all intermediate parts (external sensors, nerves, other neurons, etc). I.e. it
is more like to directly feed engine with gas and electricity to create a
spark to make it revolve completely skipping engine control unit, ignition
key, clutch pedal, fuel pump.

And when they refer to memory loss due dying neuron, this is more like part of
circuit is removed which supposed to give certain reaction to certain signals,
not like "rm /home/user/file.txt" with the rest left in place. So I do not
believe thing similar to MiB is possible with this knowledge.

------
octotoad
'The mice “quickly entered a defensive, immobile crouch,” strongly suggesting
the fear memory was being recalled.'

Yes, possibly. Or maybe it had something to do with the hole that had been
drilled in their skulls and the frickin' laser beams being fired at their
brains. Pretty cool stuff though.

~~~
relix
They obviously controlled for that.

------
carbocation
The journal article can be found here:
[http://www.nature.com/nature/journal/vnfv/ncurrent/full/natu...](http://www.nature.com/nature/journal/vnfv/ncurrent/full/nature11028.html)

It doesn't seem to claim that an _individual neuron_ is the location of a
memory, but rather that triggering a small number of specific neurons is
necessary and sufficient to cause the behavior that would be consistent with
the recall of a particular fearful memory in mice, when optogenetically
triggered.

In other words, they labeled some neurons with an optogenetic receptor during
fear conditioning. Then, thanks to the optogenetic labeling they previously
did, they were able to activate this receptor (using light) in a totally
different context (one that didn't normally elicit the freezing response
associated with mouse fear). When they did so, the mouse exhibited the
freezing response. When they ablate these neurons, there is no fear response.
The conclusion is that these neurons are necessary and sufficient to encode
the fear memory.

 _Caveat lector_ : my summary is based on the _abstract_ so I am just
parroting what they have concluded; I haven't read the paper's methods and
results for myself. Also, this is the "near-final" version published in
advance online today. It may change for final publication.

------
zerostar07
Impressive as this may sound this is not the first study of its kind. Studies
since 2009 (mentioned in the abstract) in the amygdala have been able to
direct and inactivate fear memories in a reversible manner via optogenetics
again (see <http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2844777/>) . In these
studies killing as much as 15% of the cells did not erase the memory,
indicating that it's ensembles, not single neurons that encode fear memories.

To complicate the picture even more, each neuron is part of more than one
memory engrams, and memories are stored in synaptic connections which are
formed in the vast dendritic trees of neurons. So you have a very sparse and
reduntant encoding of this associative memory.

Finally, note that both the amygdala and the hippocampus are very old
structures so we don't know if the same processes take place in the neocortex
(although it's likely so).

I don't mean to belittle the article, but it's mostly proof of concept if you
have followed the relative literature. Tonegawa's lab had some even more
fascinating papers published recently that probe the process of memory
encoding to the level of single dendrites.

------
stiff
Here is a simple explanation of the experiment:

1\. The set of neurons that was active only during learning was determined.

2\. The genes activated in those neurons were determined.

3\. Genetic engineering was done to make the activation of those genes always
happen in conjunction with activation of the gene being responsible for the
neuron becoming sensitive to light.

4\. The mouse was put through a learning experience, during which the small
group of neurons affected became sensitive to light.

5\. Via stimulating those neurons with light, the experience was reproduced in
the mouse in a completely different environment (so the comparisions to Pavlov
are not justified).

In this way the abstract concept of a memory and of the process of remembering
something was related very closely to a specific physical phenomena. Even the
methods used to make the experiment are interesting by themselves (at least
for a lay person) and I think you cannot easily dismiss the importance of this
discovery as some people do here. Please read the article here to get a better
picture:

[http://www.mit.edu/newsoffice/2012/conjuring-memories-
artifi...](http://www.mit.edu/newsoffice/2012/conjuring-memories-
artificially-0322.html)

------
mckoss
I wish I could block all extremetech stories from My HN feed. The are
universally overhyped, never the original source, often draw unjustified
conclusions, and are a pain to read (at least on an iPad - they use a non
standard interface and pop overs).

~~~
aw3c2
Maybe some "flag this" concensus would work.

------
espeed
MIT scientist Sebastian Seung talked about this possibility in his 2010 TED
talk, "I am my connectome" (<http://www.ted.com/talks/sebastian_seung.html>).

------
debacle
I think this has been overhyped just a bit. I realize that a discovery of this
nature is a big deal, but it's not what journalists are making it out to be.

------
mistercow
>MIT researchers have shown, for the first time ever, that memories are stored
in specific brain cells. By triggering a single neuron, the researchers were
able to force the subject to recall a specific memory. By removing this
neuron, the subject would lose that memory.

That's incredibly poor reasoning. Using the same logic, I can "show, for the
first time ever" that C structures are stored in individual memory pointers.

------
danmaz74
I read the MIT news piece and didn't find any reference to the removal of a
neuron that would eliminate the memory. Was that in a longer research paper?

------
zallarak
My brother, who is studying in medical school right now pointed this out to
me: "the whole time i was reading this though, i was bothered by what usually
bothers me about studies regarding the mechanics of the brain, which is that
we dont know our measures of "activation" are sufficient for determining a
causal relationship between activation of certain neurons and the recall of
certain memories."

------
wtvanhest
Off topic: I live across the river from MIT. I work in asset management and
worked for an angel investment fund. I'm working on a startup at night. If you
live in Boston and want to meet for coffee email me.

I'll meet anyone from HN, even if you just want some career advice for working
in asset management or just want to talk about random stuff.

My email address is my hn username at gmail.

------
joshaidan
Maybe this means we can finally build a machine like the one in the matrix
that lets us bootstrap our brains with kungfu.

But more importantly, I think the most significant result of this research,
should even a bit of it prove to be true, is the possibility that it could
help us understand, and maybe even prevent dementia. That's exciting!

~~~
carbocation
Sadly, and I mean very sadly, this doesn't mean that. =)

The reason it doesn't mean that is that they are triggering naturally-
programmed neurons via light. They are not programming them via light.

------
ilitirit
> The question now, though, is how memories are actually encoded — can we
> programmatically create new memories and thus learn entire subjects by
> inserting a laser into our brain?

That's a pretty scary area of technology. I hope that as a civilization we
will become responsible enough to use that before we discover how.

------
j45
I wonder if by deleting not so nice memories (i'm guessing that would be one
of the first applications) the person will continue to make the same decisions
over and over, because they might not remember them and keep re-experiencing
(and learning) repeatedly?

------
kghose
If you are interested in this sort of thing (memory storage in the brain,
recall etc.) you might be interested in Wilder Penfield's work. (e.g.
<http://primal-page.com/penfield.htm>)

------
deadmike
"The mice 'quickly entered a defensive, immobile crouch,' strongly suggesting
the fear memory was being recalled."

Perhaps the defensive, immobile crouch had something to do with having a hole
drilled through their skull and a laser shined through said hole?

------
holeinskull
<you drill a hole through the subject’s skull and point the laser at a small
cluster of neurons, the mice quickly entered a defensive state>

    
    
      This is a expected  response and perhaps has nothing to do with remembering.

------
PaulGrinsBig
This article sucks, the quality of online journalism has taken a new
low...there are no citations...just rambling that eventually one finds to be a
total misunderstanding of the results and of science in general...ahhhh...

------
aidos
There was a Ted talk some time ago about the work on optogenetics (in fruit
flies I think) <http://www.ted.com/talks/gero_miesenboeck.html>

------
cdcox
That title is incorrect. These researchers did not stimulate one neuron to
activate one memory. They stimulated a group of neurons in one region using a
fiber optic.

I'll go through the experiment for those who don't really get the write up.
Quick background:

0\. Neurons are specialized cells in your brain, their firing is the basis of
cognition. Neurons that fire strongly together tend to get linked. Not all
your neurons are firing all at once. Not all neurons participate in a memory,
but a large collection (0.1-4% depending on brain region) are used for each
memory. (at least in naive mice) Memories are highly distributed across brain
regions and within brain regions.

1\. There is a gene 'cFos' that turns on in neurons that undergo activity. It
is very short lasting, about an hour, and then it is back down. It is very
cell specific, only cells used have been activated will show this gene.

2\. There is a genetically inducable protein you can put in cells so that when
you shine them with light they will start firing.

3\. Anything genetically inducible can have a tag added that will make it
impossible to induce when an animal is on a specific drug. (We'll call it
Dox.)

The researchers made it so that when cFos is activated, it will transcribe the
inducible light activated channel. But, it will only do this when the animal
isn't on Dox. So they took the animal off Dox, exposed it to fear conditioning
(they shocked it in a unique box), then put it back on Dox. So only the cells
that were active during the fear conditioning will be turn on when they shine
light.

They then put the animal in a new box and shined light, and the animal froze.
(A sign it was afraid) They concluded that activating cells that had been
active during the storing of the memory can 'reactivate' the memory, even out
of it's context.

Of course there are a few major problems with this. The region of the brain
they worked in is a relatively minor area of the brain. They admit in the
course of the paper that each cell is used to store many memories. (They claim
the assembly of cells activate the memory? But they never bother testing
this.) Their firing pattern is far from physiological. The mice who underwent
this 'memory reactivation' did not freeze as much as mice in normal fear
conditioning and did not seem to learn the 'reactivated memory' at all.
(Though again they didn't really bother testing this.) Normal fear-memory is
learned quite well. This is a very preliminary but very important study in the
field. It will be interesting to see how they follow this up.

Also, the Npas4 stuff is completely irrelevant to this article. There are
countless markers that when 'knocked out' make it impossible to store memory.

Also here is a (paywalled) link to the
paper:[http://www.nature.com/nature/journal/vnfv/ncurrent/full/natu...](http://www.nature.com/nature/journal/vnfv/ncurrent/full/nature11028.html)

Here is a link to another (paywalled) paper which came out today which did
almost the same thing and say almost opposite results (the details explain
this oddity): <http://www.sciencemag.org/content/335/6075/1513.full?rss=1>

Here is a (paywalled) more layperson write up to the second article:
<http://www.sciencemag.org/content/335/6075/1455.full>

------
jpwagner
[http://blogs.nature.com/actionpotential/2012/03/fear-of-
the-...](http://blogs.nature.com/actionpotential/2012/03/fear-of-the-
light.html)

------
isa
Besides the fact that the scientists used trauma to retrieve their data, what
a beautiful notion: collecting a memory at the tip of every neuron.

------
Craiggybear
I don't believe a word of this. It isn't _proof_ of any such a process. This
to me appears as inappropriate reductionism.

The brain is highly volatile both chemically and physically and is changing
minute by minute. The notion that a memory belongs to a single group or
cluster of neurons is absurd. They are constantly being reordered and
reprioritised and changed throughout the lifetime of the animal. And being
lost due to chemical damage and the effects of ageing and free radicals.

The nature of memory and conciousness isn't just the physical existence of
neurons. Who _you_ are is more than the sum of the parts.

The mind is also as much a process of the body -- your conciousness and mind
grows within it from birth and a large part of who you are is as much a
product of that, its hormones and its metabolic chemistry as anything that
resides solely between the ears alone.

------
stefantalpalaru
The Nature abstract is about a "population of neurons" and triggering a memory
related behavior while the extremetech article talks about "specific brain
cells" and memory storage.

Nothing to see here, move along.

------
rsanchez1
I always take these with a grain of salt. One day a study comes out saying
that memories are not stored in a specific location, that scientists can cut
out large portions of mice brain and the mice will retain memories, and the
next day a study comes out that specific memories can be created or destroyed
with specific neurons.

------
bburns
There's an obligatory Eternal Sunshine of the Spotless Mind reference to be
made here...

~~~
debacle
There was an Eternal Sunshine of the Spotless Mind reference in the article.
You should have read it.

