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Neurogenesis and Learning

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Синапсис, нейроны и мозг

Еврейский университет в Иерусалиме

4.8 (оценок: 756) | Зарегистрировано учащихся: 47K

These are very unique times for brain research. The aperitif for the course will thus highlight the present “brain-excitements” worldwide. You will then become intimately acquainted with the operational principles of neuronal “life-ware” (synapses, neurons and the networks that they form) and consequently, on how neurons behave as computational microchips and how they plastically and constantly change - a process that underlies learning and memory. Recent heroic attempts to realistically simulate large cortical networks in the computer will be highlighted (e.g., “the Blue Brain Project”) and processes related to perception, cognition and emotions in the brain will be discussed. For dessert we will deliberate on the future of brain research, including the questions of “brain and art”, consciousness and free will. For more information see the course promo below and read “About the course.”

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4.8 (оценок: 756)

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LD

Sep 17, 2018

up to date with current developments.\n\nmakes you think, and not just memorize some abstract ideas / equations.\n\nI enjoyed it, highly recommend to others.\n\nThanks for the Course!

ET

May 16, 2017

Mind-boggling, mind-expanding, and endlessly fascinating. Hard-going, too, and requiring a fair amount of additional research inorder to answer the quizzes. But definitely worth it!

Из урока

Neurons as Plastic/Dynamic Devices

This module discusses "Neurons as plastic/changing devices". Probably the most unique aspect of the nervous tissue is its amazing capability to constantly and adaptively change in response to a challenging environment; this capability enables us to learn and to store memories. We start by a short discussion about the notion of learning in the brain and then highlight various mechanisms that support learning and memory – introducing the term ‘neuronal plasticity”. In particular “functional plasticity”, whereby the efficacy of existing synapses is changed as well as “structural plasticity”, whereby learning/memory processes are associated with anatomical changes - the formation of new synaptic connections and with neurogenesis – the birth of new nerve cells (yes, also in the adult brain). A mathematical model that captures some aspects of functional plasticity will also be introduced together with several new exciting experimental finding related to “neuronal plasticity”.

The Brain Learns22:36

Mechanisms Sub-Serving Learning and Memory11:58

Functional Plasticity17:50

Structural Plasticity10:48

Neurogenesis and Learning18:03

Преподаватели

Idan Segev
Professor

Текст видео

Okay. So let's go to the third possibility that

we discussed. And this is the very controversial issue,

whether newborn cells in the adult brain, often mammalians, like ourselves, exist.

This is called a neurogenesis. Though you have new born cells.

Is there a neurogenesis, in the mammalian, adult mammalian brain.

We know that there is neurogenesis, that there are new born cells.

For example, in song birds. We know that in some birds, in avians,

there is a region in the brain whereby neurons are born in the adult male brain

of the bird when there is a generation of the song.

So each period this, the, the bird starts to re-sing its particular song for a

given species, and, and this new song, new song, new singing of the bird is

associated clearly with the addition of a large amount of new cells.

This was neurogenesis in avians, in birds.

asking whether there is a newborn system of cells in the mammalian brain.

This was very controversial. Until very recently, we thought that

there are, no, that you are born with a given amount of cell, at least for a

given period of time Until you're mature and there are no newborn cells in our

brain. Or in the mouse brain.

So for example this was a big controversy eh, well known scientists from Yale said,

not a single heavily labelled cell with the morphological characteristic of a

neuron in any brain, of any adult animal. Any new, newborn cell and he concluded

all neurons of the rhesus monkeys all neurons in teh rhesus monkeys are

generated during prenatal and early postnatal life so early on there are

newborn cells of course than there stabilized there are no indications of

new born cells in that downgrade. But then in 1997 Elizabeth Gould a

professor assistant professor of neuroscience in Princeton claimed she

does see neurogenesis first in three shoes And later on also in monkeys.

this start to be very controversial, but now today we have new techniques that

enable us to mark specifically stem cells, newborn cells, in the adult brain

of mouse and of human. And we know today That there are at least

2 regions, maybe more, at least 2 regions in the brain that constantly generate new

born cells, new stem cells in the adult brain.

This is one example of this staining technique.

this is by Elizabeth Gould showing that these red cells are newborn cells and

newborn cells following a challenging mouse water maze for the mouse and there

are newborn cells in the hippocampus we mention hippocampus a learning region in

the brain So this was indications of, because you have specific markers to

newborn stems, you can see aha, our newborn stems.

And now today for example at the Hebrew University of[UNKNOWN], using the

2-footed microscope and this staining technique, for newborn cells, stem cells.

He's working on olfactory system. Not the hypo-campus but the olfactory

system. He already, he showed the very beautiful

experiment. That indeed in the olfactory system of

the mouth there are newborn cells that are integrated in the system.

Develop dendrites, become more extend, extended, making synopsis, making

dendrites. Some of them die out, some of them

remain, not very clear who is about to die out, the new ones, who remain as part

of the system but clearly, the, a newborn cells in the adult mouse in the factory

system and also in the hippocampus so this really changes the dogma the dogma

that we don't have newborn cells. We don't have newborn cells is wrong

there are two regions the Hippocampus also in our case ad the factory bar the

factory system of the mouse there are newborn cells constantly being born,

thousand of them every day. So what we know today -- so- -- sorry --

what we know today is that also human in the hippocampus generate newborn cells

And these newborn cells are associated with a certain type of behavior or

improvement of behavior, and apparently, and this is a very interesting case,

where you challenge a mouse in this case with a very particular conditioning task,

the mouse has to remember to respond to a tone if there was a tone here.

He has to hold until presses the letter, for example, yes, and the task becomes

more difficult with the gap between the sound and the reaction.

He has to learn that he has to wait enough time.

The more challenging the task is, so this is a challenging task, you have to wait a

long time And this is less challenging task and, and so on.

The more challenging task you have, the more newborn cells you develop.

So there is a correlation between the birth of new cells.

And we know actually today that these newborn cells are born as stem cells, in

a particular niche Of the hippocampus, and they are migrated, they are migrated

into a particular region of the hippocampus.

And they become mature. They become involved.

They become branched. They become part of the network, some of

them. And some of them die out and this is an

ongoing process. And those that remain apparently some of

them are functioning, of course, for the network, and some of them remain alive,

so to speak, for longer time, as a function of the challenges that the brain

is facing. So there is the relationship between the

number of newborn cells and the capability to to do new functions

apparently that's not completely finalized this what I just said but it's

clear that there is newborn cells some of them are integrated in the network in the

adult mammal brain so that's a different than the old dogma now.

One issue about these cells of course, and that's ongoing studies [UNKNOWN] in

others who are they integrated with? What makes them stable or not?

This is an ongoing research, because all what I'm telling you now is relatively

new. One clear is that we would like to

understand better, this phenomena of neurogenesis, because it provides hope

for therapies. Suppose you have a region in the brain

where cells deteriorate, dissolve. Can you rehabilitate?

Can you improve brain capabilities, for example in Alzheimer's?

Some how encouraging neurogenesis. There is neurogenesis but can we

encourage more neurogenesis. Why in some regions like hippocampus we

have neurogenesis, new born cells? In some region after a stroke you don't

have neurogenesis. We would like to understand it, and this

would be extremely important for. For disease, for, for im-, for, for

ameliorating diseases. So I would like to summarize and say

about this aspect of plastic brain. One thing is clear, the old notion of

saying if you don't use it you lose it, is apparently correct.

The more you use the network, a challenging environment, an intellectual

task, motor activity, the more you challenge the network, the more new

connections you have, more spines. The more new cells you have in the

hippocampus then you have to learn something new.

So the interaction between activity behavior and this plastic system that

would like to change, so much would like to change, is about creating new spines

and synapses, making the synapses more strong or weak.

All newborn cells can really eventually influence your behavior.

So you should be active, that's the message.

So cognitive training programs can provide benefits.

Physical benefits for the brain, for in health enhancement certain capabilities,

that's a very important message for all of us.

Let me complete This lecture, it is rather sparse but at least, I hope,

giving you an indication of the status of the field, so to speak, today of memory

and learning in the brain, about some anecdotes and questions that emerge from

this study. Some anecdotes.

Maybe many of you have heard About this classical FMRI, or MRI, experiment

whereby you look at the brain of taxi drivers.

And the finding was that these taxi drivers that are really in London and

practicing to remember all these thousands, and tens of thousands of

streets and stores and locations really high demand on the hippocampus of the

taxi drivers in London. Apparently, there is a acorrelation

between years of experience as a taxi driver learning the streets of London

and, and, and the volume, and the gray matter volume in the hippocampus.

This is somewhat controversial but, from what we just learn, is indeed the

challenges of this hippocampus of the taxi drivers to remember so many streets

and and, and so many addresses. Maybe there are newborn cells in the

hippocampus that are stabilized. Enabling the taxi drivers in London to

remember all these cells. There are other studies, many studies,

actually, showing that when you are an expert in something, for example, if you

are a musician; you very, very good in playing the violin or the piano, then

certain regions of your brain, the motor cortex, the auditory cortex, region

involved With this particular expertise. Increasing volume, whether this

increasing volume results from most spines or for most[UNKNOWN] , not very

clear. But there is this correlation and now I

think you better understand what could be the underlying mechanism for this

Non-invasive recording of brain regions that becomes bigger following, so,

following for an experiment. So that's one aspect that I want to

connect, because you may have heard this experiments.

Now you know something about this cellular mechanism.

Let me touch very fast about controversial issues.

Or not controversial necessarily, but issues related to plasticity and

learning. One aspect, and I already mentioned it,

one of our amazing capabilities to change constantly.

I know that after my talk, both my brain, and I hope your brain, have changed.

You have new synapses or new spines, maybe even new cells Born after my talk,

because you may remember some of it. But, so we are learning machines, but

computers are typically not learning anything new.

The computer, in terms of its hardware, its connectivity, its pattern of

activity. So, there is a whole new field, a whole

new field it called, it is called machine learning field in computer science.

Whereby they are trying to develop algorithms and methods for he machine to

learn and we are fantastic example of a machine that automatically built in in

real time learning . Can we learn from the physics of the

brain, how to develop sophisticated learning machines because if the machines

will not learn they will never. Be even close to what we can do in real

environment. So that's one issue I wanted to

highlight. The machine learning field.

Now we can ask yourself, how can you trust memories?

You'll go to a trial, you'll go to a judge.

You want to remember something. How can you trust your memory?

[INAUDIBLE] not really I don't think that the role of memory is to embed forever a

particular memory. The whole notion of memory is to try to

assosciate and change constantly while you experience new thing to associate now

what you've learned to something that you've learned before So memory has to be

versatile, has to be flexible. And this flexibility may really harm, so

to speak, a given memory. And there are beautiful new ex-and

experiments showing, that when you use the memory now, when you bring out the

memory now. The fact that you now bring it out with

the new association, because it's not the old memory, but now it's a, the memory in

a new environment already changed the memory.

So it's not a fixed thing, the memory. We should not look at it as a picture

that's in the camera that remains the same picture.

Or in the computer the same, the same word file remains the same word file, no.

The memories are very flexible that enables[INAUDIBLE] mechanism enables us

to interact with the world, and change our perception of things on going.

It's not a trustworthy reliable forever. Could we read out memories?

Could they look a your mind and say now you remember you mother, now you remember

your childhood. Can i do it?

The general answer is no because you code the particular memory with a given

network that is particular to you. You code the color red differently than I

code the color red. We then agree that when we look at

something, it's red for you, it's red for me.

But the coding, the spikes, the synapses, the particular neurons involved in, in

your red, in your association of red with a rose.

My association of red with maybe blond is different.

So I cannot just look at your brain now and say now you think about red.

If I look at your brain enough times and I decode your particular brain, I develop

a polygraph for your particular brain, then I may be able to read something

About your particular encoding or coding of a particular item.

So it's not going to be disc on key because we don't have a common disc.

You have your own brain and discs. And I have my own brain and discs.

We cannot exchange easily discs. Language helps to exchange discs.

And finally, I want to ask could we embed new memories?

Can I stimulate your brain and embed new memory?

Of course I can do it. I can embed new memory now that I teach

you. So I embed new memory in your brain.

I can stimulate your brain. I can erase memories.

I can destroy synapses, I can intervene with your brain.

That's true. But I cannot really, in particular, embed

a face, because I really don't know how to really manipulate your network so

whenever this network is active, it is associated with a given item.

I have to correlate the item with a network.

So I have to stimulate it and then show you something.

Stimulate the network, show you something.

Then you do the correlation, you do the association.

I cannot really embed a face, unlike many movies.

So our brain is very unique, very particular, and it requires a very, very

specific network to be active Associated with something on the outside.

Then you make the association, then the memory is embedded.

And as I mentioned earlier, you have also to act, you have to behave if you want to

perceive, like in the case of the twin case.

So, thank you very much for listening to this lesson number 5.

This was an attempt to integrate data from anatomy, synaptic physiology,

spikes, and new experiments about the brain related to a fascinating phenomena,

memory. In the next lesson, we should talk about

another aspect of the brain, computation. we are a computing machine And I want to

show you how neurons, dendrites, synapses and spikes can compute, can be used for

computation. So see you next week.

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