Neil Burgess: How your brain tells you where you are

Prevodilac: Silvija Varga Lektor: Tatjana Jevdjic

When we park in a big parking lot,

Kada se parkiramo na parkingu,

how do we remember where we parked our car?

kako se sećamo gde smo ostavili svoj automobil?

Here's the problem facing Homer.

Ovo je problem sa kojim se Homer suočava.

And we're going to try to understand

Pokušaćemo da razumemo

what's happening in his brain.

šta se dešava u njegovom mozgu.

So we'll start with the hippocampus, shown in yellow,

Dakle, počećemo sa hipokampusom, prikazanim žutom bojom,

which is the organ of memory.

koji je organ memorije.

If you have damage there, like in Alzheimer's,

Ako tu imate oštećenje, kao kod Alchajmerove bolesti,

you can't remember things including where you parked your car.

ne možete da se setite stvari, uključujući i gde ste parkirali auto.

It's named after Latin for "seahorse,"

Nazvan je "morski konjić" na latinskom,

which it resembles.

na kojeg i liči.

And like the rest of the brain, it's made of neurons.

Kao i ostatak mozga, sačinjen je od neurona.

So the human brain

Dakle, ljudski mozak

has about a hundred billion neurons in it.

ima oko stotinu milijardi neurona.

And the neurons communicate with each other

Neuroni komuniciraju između sebe

by sending little pulses or spikes of electricity

slanjem malih električnih potencijala

via connections to each other.

preko međusobnih veza.

The hippocampus is formed of two sheets of cells,

Hipokampus je građen od dva sloja ćelija,

which are very densely interconnected.

koji su veoma gusto povezani.

And scientists have begun to understand

Naučnici počinju da shvataju

how spatial memory works

kako pamćenje prostora funkcioniše

by recording from individual neurons

beleženjem aktivnosti pojedinačnih neurona

in rats or mice

pacova i miševa,

while they forage or explore an environment

dok tragaju za hranom ili istražuju okolinu

looking for food.

tražeći hranu.

So we're going to imagine we're recording from a single neuron

Dakle, zamislićemo da snimamo pojedinačni neuron

in the hippocampus of this rat here.

hipokampusa ovog pacova.

And when it fires a little spike of electricity,

Kada neuron okine električni potencijal

there's going to be a red dot and a click.

pojaviće se crvena tačka i klik.

So what we see

Dakle, ono što vidimo

is that this neuron knows

je da ovaj neuron zna

whenever the rat has gone into one particular place in its environment.

kad god je pacov otišao na određeno mesto u svojoj okolini.

And it signals to the rest of the brain

On to signalizira ostatku mozga

by sending a little electrical spike.

šaljući male impulse elektriciteta.

So we could show the firing rate of that neuron

Dakle, možemo da prikažemo obrazac okidanja tog neurona

as a function of the animal's location.

kao funkciju položaja te životnje u prostoru.

And if we record from lots of different neurons,

Ako snimimo aktivnost više neurona,

we'll see that different neurons fire

videćemo da različiti neuroni šalju impulse

when the animal goes in different parts of its environment,

kada životinja ide na različita mesta te sredine,

like in this square box shown here.

kao u ovoj kvadratnoj kutiji.

So together they form a map

Dakle, oni zajedno formiraju mapu

for the rest of the brain,

namenjenu ostatku mozga

telling the brain continually,

obaveštavajući ga neprekidno:

"Where am I now within my environment?"

"Gde sam sad u svom okruženju?"

Place cells are also being recorded in humans.

"Ćelije mesta" su nađene i kod ljudi.

So epilepsy patients sometimes need

Tako je pacijentima sa epilepsijom potrebno

the electrical activity in their brain monitoring.

nadgledanje električne aktivnosti mozga.

And some of these patients played a video game

Neki od ovih pacijenata igrali su video igricu

where they drive around a small town.

u kojoj su se vozili po malom gradu.

And place cells in their hippocampi would fire, become active,

Ćelije mesta njihovog hipokampusa bi se aktivirale

start sending electrical impulses

i slale električne impulse

whenever they drove through a particular location in that town.

kad god bi prolazili pored određenog mesta u tom gradu.

So how does a place cell know

Kako ćelije mesta znaju

where the rat or person is within its environment?

gde je pacov ili čovek unutar svoje okoline?

Well these two cells here

Ove dve ćelije

show us that the boundaries of the environment

nam pokazuju da su granice sredine

are particularly important.

posebno važne.

So the one on the top

Dakle, ova na vrhu

likes to fire sort of midway between the walls

voli da šalje signal nekako na pola puta između zidova

of the box that their rat's in.

kutije u kojoj je pacov.

And when you expand the box, the firing location expands.

A kada proširite kutiju, prostor slanja signala se širi.

The one below likes to fire

Ova ispod voli da šalje signal

whenever there's a wall close by to the south.

kad god je u blizini južnog zida kutije.

And if you put another wall inside the box,

Ako postavite još jedan zid unutar kutije,

then the cell fires in both place

tada ćelija okida impulse na oba mesta

wherever there's a wall to the south

kad god postoji zid na jugu,

as the animal explores around in its box.

dok životnja istražuje okolo unutar kutije.

So this predicts

Dakle, ovim se predviđa

that sensing the distances and directions of boundaries around you --

da je percepcija graničnih udaljenosti i pravaca oko vas

extended buildings and so on --

uključujući i zgrade i slično -

is particularly important for the hippocampus.

posebno važna za hipokampus.

And indeed, on the inputs to the hippocampus,

Zaista, u aferentnim putevima hipokampusa,

cells are found which project into the hippocampus,

su ćelije koje se projektuju u hipokampus,

which do respond exactly

koje reaguju upravo

to detecting boundaries or edges

pri otkrivanju granica i ivica

at particular distances and directions

na određenim odstojanjima i pravcima

from the rat or mouse

od pacova ili miša,

as it's exploring around.

dok se on kreće i istražuje okolinu.

So the cell on the left, you can see,

Dakle, ćelija levo, kao što možete videti,

it fires whenever the animal gets near

okida kad god se životinja približi

to a wall or a boundary to the east,

zidu ili granici na istoku,

whether it's the edge or the wall of a square box

bilo da je to ivica ili zid kvadratne kutije

or the circular wall of the circular box

ili kružni zid kružne kutije

or even the drop at the edge of a table, which the animals are running around.

ili čak ivica stola po kom životnja trči.

And the cell on the right there

A ova ćelija desno

fires whenever there's a boundary to the south,

ispaljuje kad god postoji granica na jugu,

whether it's the drop at the edge of the table or a wall

bez obzira da li je to ivica stola ili zid

or even the gap between two tables that are pulled apart.

ili čak prostor između dva razdvojena stola.

So that's one way in which we think

Mislimo da je to jedan način koji koriste

place cells determine where the animal is as it's exploring around.

ćelije mesta da bi odredile položaj životinje, dok istražuje okolinu.

We can also test where we think objects are,

Takođe možemo ispitati gde mislimo da su objekti,

like this goal flag, in simple environments --

kao što je ova zastavica, u jednostavnoj sredini

or indeed, where your car would be.

ili u stvarnosti, gde bi mogao biti vaš auto.

So we can have people explore an environment

Tako, možemo imati i ljude koji istražuju okolinu

and see the location they have to remember.

i vide mesto koje treba da zapamte.

And then, if we put them back in the environment,

I onda, ako ih vratimo nazad u tu sredinu,

generally they're quite good at putting a marker down

u većini slučajeva odrede mesto

where they thought that flag or their car was.

gde misle da su bili zastavica ili automobil.

But on some trials,

Ali u nekim ispitivanjima,

we could change the shape and size of the environment

možemo da promenimo oblik i veličinu okoline

like we did with the place cell.

kao što smo uradili sa ćelijom mesta.

In that case, we can see

U tom slučaju, možemo videti

how where they think the flag had been changes

kako se njihovo sećanje na položaj zastavice menja

as a function of how you change the shape and size of the environment.

zavisno od naše promene izgleda i veličine okoline.

And what you see, for example,

I ono što možete videti, na primer,

if the flag was where that cross was in a small square environment,

ako je zastavica bila na mestu ovog krsta u malom kvadratu

and then if you ask people where it was,

i onda ih pitate gde je bila,

but you've made the environment bigger,

a vi ste u međuvremenu učinili prostor većim,

where they think the flag had been

mesto gde misle da je bila zastavica

stretches out in exactly the same way

se izdužuje na isti način

that the place cell firing stretched out.

kao što se izdužio prostor aktivnosti ćelija mesta.

It's as if you remember where the flag was

To je kao da se sećate gde je zastavica bila

by storing the pattern of firing across all of your place cells

čuvanjem obrazaca okidanja duž svih svojih ćelija mesta

at that location,

na zadatoj lokaciji,

and then you can get back to that location

onda možete da se vratite na to mesto

by moving around

krećući se okolo,

so that you best match the current pattern of firing of your place cells

tako da najbolje usaglasite trenutni obrazac okidanja ćelija mesta

with that stored pattern.

sa već sačuvanim obrascem.

That guides you back to the location that you want to remember.

Ovo vas vodi nazad na mesto koje želite da zapamtite.

But we also know where we are through movement.

Ali, mi znamo gde se nalazimo i pomoću kretanja.

So if we take some outbound path --

Ako posmatramo neki put odlaska -

perhaps we park and we wander off --

kao kad se parkiramo i posle odlutamo -

we know because our own movements,

znamo uz pomoć sopstvenog kretanja,

which we can integrate over this path

koje možemo da integrišemo preko ovog puta

roughly what the heading direction is to go back.

i tako grubo da odredimo glavni pravac povratka.

And place cells also get this kind of path integration input

Ćelije mesta takođe dobijaju ovako integrisani unos

from a kind of cell called a grid cell.

preko ćelija koje zovemo "ćelijama rešetke".

Now grid cells are found, again,

Ovakve ćelije se nalaze

on the inputs to the hippocampus,

u aferentima hipokampusa

and they're a bit like place cells.

i liče na ćelije mesta.

But now as the rat explores around,

Ali sada, kad pacov istražuje

each individual cell fires

svaka ćelija okida impulse

in a whole array of different locations

sa niza različitih mesta

which are laid out across the environment

i one su raspoređene po celom prostoru

in an amazingly regular triangular grid.

u obliku zapanjujuće pravilne rešetkaste mreže trouglova.

And if you record from several grid cells --

Ako beležite aktivnost različitih ćelija rešetke -

shown here in different colors --

prikazanih ovde u različitim bojama -

each one has a grid-like firing pattern across the environment,

svaka prostorno ima obrazac aktivnosti u vidu rešetkaste mreže

and each cell's grid-like firing pattern is shifted slightly

i svaki pojedinačni obrazac okidanja je malo pomeren

relative to the other cells.

u odnosu na druge ćelije.

So the red one fires on this grid

Crvena je aktivna na ovoj mreži

and the green one on this one and the blue on on this one.

zelena na ovoj, a plava na ovoj.

So together, it's as if the rat

Zajedno, čini se da pacov

can put a virtual grid of firing locations

može da postavi virtuelnu mrežu obrazaca ovih aktivnosti

across its environment --

preko celog prostora,

a bit like the latitude and longitude lines that you'd find on a map,

slično linijama geografske dužine i širine na mapi,

but using triangles.

ali koristeći trouglove.

And as it moves around,

Kako se kreće unaokolo,

the electrical activity can pass

električna aktivnost može da pređe

from one of these cells to the next cell

sa jedne od ovih ćelija na sledeću

to keep track of where it is,

pamteći tako gde se nalazi,

so that it can use its own movements

tako da koristi sopstveno kretanje

to know where it is in its environment.

da bi znao gde se nalazi u prostoru.

Do people have grid cells?

Da li ljudi imaju ove ćelije rešetke?

Well because all of the grid-like firing patterns

S obzirom da svi rešetkasti obrasci okidanja u vidu mreže

have the same axes of symmetry,

imaju istu osu simetrije,

the same orientations of grid, shown in orange here,

odnosno iste orijentacije mreža, prikazane narandžasto,

it means that the net activity

znači da bi ukupna aktivnost

of all of the grid cells in a particular part of the brain

svih ćelija rešetke u određenom delu mozga

should change

trebalo da se promeni

according to whether we're running along these six directions

zavisno od toga da li se krećemo duž ovih šest pravaca

or running along one of the six directions in between.

ili ovih šest pravaca između njih.

So we can put people in an MRI scanner

Možemo da stavimo ljude u skener magnetne rezonance

and have them do a little video game

damo im zadatak kao video igricu

like the one I showed you

kao ona koju sam već prikazao

and look for this signal.

i posmatramo ovaj signal.

And indeed, you do see it in the human entorhinal cortex,

I zaista, to vidite u ljudskom entorinalnom korteksu,

which is the same part of the brain that you see grid cells in rats.

što odgovara delu mozga pacova koji sadrži ćelije rešetke.

So back to Homer.

Dakle, vratimo se Homeru.

He's probably remembering where his car was

Verovatno se seća gde mu je automobil,

in terms of the distances and directions

u funkciji udaljenosti i pravaca

to extended buildings and boundaries

uključujući zgrade i granice

around the location where he parked.

oko mesta gde se parkirao.

And that would be represented

To bi bilo predstavljeno

by the firing of boundary-detecting cells.

okidanjem ćelija koje detektuju granice.

He's also remembering the path he took out of the car park,

On se takođe seća puta kojim je izašao iz parkinga,

which would be represented in the firing of grid cells.

što bi bilo predstavljeno aktivnošću ćelija rešetke.

Now both of these kinds of cells

Obe ove vrste ćelija

can make the place cells fire.

mogu da aktiviraju ćelije mesta.

And he can return to the location where he parked

On će se vratiti na mesto gde je parkirao

by moving so as to find where it is

krećući se i pokušavajući da pronađe

that best matches the firing pattern

najbolje preklapanje sadašnjeg obrasca

of the place cells in his brain currently

aktivnosti ćelija mesta

with the stored pattern where he parked his car.

sa već sačuvanim obrascem gde je parkirao auto.

And that guides him back to that location

To ga navodi na lokaciju

irrespective of visual cues

bez obzira na vizualne znakove

like whether his car's actually there.

da li je njegov automobil zapravo tamo.

Maybe it's been towed.

Možda ga je "pauk" odneo.

But he knows where it was, so he knows to go and get it.

Ali zna gde je bio i zna do njega da dođe.

So beyond spatial memory,

Osim pamćenja prostora,

if we look for this grid-like firing pattern

ako posmatramo ovaj rešetkasti obrazac aktivnosti

throughout the whole brain,

u celom mozgu,

we see it in a whole series of locations

vidimo ga u raznim delovima

which are always active

koji su uvek aktivni

when we do all kinds of autobiographical memory tasks,

kad obavljamo različite autobiografske memorijske aktivnosti,

like remembering the last time you went to a wedding, for example.

npr. kao što je sećanje kad ste poslednji put bili na venčanju.

So it may be that the neural mechanisms

Moguće je da se neuronski mehanizmi

for representing the space around us

za predstavljanje prostora oko nas

are also used for generating visual imagery

takođe koriste za stvaranje vizuelnog sećanja,

so that we can recreate the spatial scene, at least,

tako da možemo da rekonstruišemo prostornu scenu

of the events that have happened to us when we want to imagine them.

onoga što smo doživeli kada želimo da je zamislimo.

So if this was happening,

Ako se ovo dešava,

your memories could start by place cells activating each other

vaše sećanje bi moglo da započne tako što ćelije mesta aktiviraju jedna drugu

via these dense interconnections

preko međusobnih gustih veza,

and then reactivating boundary cells

a zatim reaktiviraju ćelije granice

to create the spatial structure

da bi stvorile prostorni sklop

of the scene around your viewpoint.

scene oko vaše tačke gledanja.

And grid cells could move this viewpoint through that space.

Ćelije reštke bi mogle da pomeraju ovu tačku gledanja kroz prostor.

Another kind of cell, head direction cells,

Druga vrsta ćelija, ćelije pravca glave

which I didn't mention yet,

koje još nisam pomenuo,

they fire like a compass according to which way you're facing.

okidaju kao kompas zavisno od pravca kojem ste okrenuti.

They could define the viewing direction

One bi mogle da definišu pravac gledanja

from which you want to generate an image for your visual imagery,

iz kog ćete stvoriti sliku svog vizuelnog sećanja

so you can imagine what happened when you were at this wedding, for example.

tako da možete da zamislite šta se dogodilo kad ste bili na tom venčanju.

So this is just one example

Ovo je samo jedan primer

of a new era really

nove ere

in cognitive neuroscience

kognitivne neuronauke

where we're beginning to understand

gde počinjemo da razumevamo

psychological processes

psihološke procese

like how you remember or imagine or even think

kao što je kako pamtite ili zamišljate ili čak razmišljate,

in terms of the actions

kao izraz aktivnosti

of the billions of individual neurons that make up our brains.

milijardi pojedinačnih neurona koji čine naš mozak.

Thank you very much.

Hvala najlepše.

(Applause)

(Aplauz)