TEDSalon London Spring 2011
Neil Burgess: How your brain tells you where you are
Neil Burgess: Kako ti mozak govori gdje se nalaziš
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Kako se sjećate gdje ste parkirali automobil? Kako znate krećete li se u pravom smjeru? Neuroznanstvenik Neil Burgess proučava neuralne mehanizme koji kodiraju prostor oko nas i način na koji su povezani s memorijom i maštom.
Neil Burgess - Neuroscientist
At University College in London, Neil Burgess researches how patterns of electrical activity in brain cells guide us through space. Full bio
At University College in London, Neil Burgess researches how patterns of electrical activity in brain cells guide us through space. Full bio
Double-click the English transcript below to play the video.
00:15
When we park in a big parking lot,
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Kada parkiramo na velikom parkiralištu,
00:17
how do we remember where we parked our car?
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kako se sjetimo gdje smo ostavili auto?
00:19
Here's the problem facing Homer.
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Ovaj problem muči Homera.
00:22
And we're going to try to understand
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Pokušat ćemo razumjeti
00:24
what's happening in his brain.
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što se događa u njegovom mozgu.
00:26
So we'll start with the hippocampus, shown in yellow,
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Počnimo s hipokampusom, koji je obojan žuto,
00:28
which is the organ of memory.
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i organ je memorije.
00:30
If you have damage there, like in Alzheimer's,
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Ako imate neko oštećenje na tom području, kao kod Alzheimerove bolesti,
00:32
you can't remember things including where you parked your car.
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ne možete zapamtiti stvari poput toga gdje ste parkirali.
00:34
It's named after Latin for "seahorse,"
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Hipokampus je dobio ime po latinskom nazivu za morskog konjica,
00:36
which it resembles.
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na kojeg izgledom podsjeća.
00:38
And like the rest of the brain, it's made of neurons.
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Kao i ostatak mozga, načinjen je od neurona.
00:40
So the human brain
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Ljudski mozak
00:42
has about a hundred billion neurons in it.
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sadrži otprilike stotinu milijardi neurona.
00:44
And the neurons communicate with each other
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Ti neuroni međusobno komuniciraju,
00:47
by sending little pulses or spikes of electricity
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šalju si male električne signale
00:49
via connections to each other.
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preko različitih veza kojima su povezani.
00:51
The hippocampus is formed of two sheets of cells,
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Hipokampus se sastoji od dvije ploče stanica
00:54
which are very densely interconnected.
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koje su vrlo gusto povezane.
00:56
And scientists have begun to understand
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Znanstvenici su počeli shvaćati
00:58
how spatial memory works
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kako funkcionira prostorna memorija
01:00
by recording from individual neurons
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snimajući aktivnost pojedinih neurona
01:02
in rats or mice
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kod štakora ili miševa
01:04
while they forage or explore an environment
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koji su istraživali okolinu
01:06
looking for food.
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u potrazi za hranom.
01:08
So we're going to imagine we're recording from a single neuron
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Sada ćemo zamisliti da snimamo aktivnost jednog neurona
01:11
in the hippocampus of this rat here.
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u hipokampusu ovog štakora ovdje.
01:14
And when it fires a little spike of electricity,
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Kada neuron bude odaslao jedan impuls elektriciteta,
01:16
there's going to be a red dot and a click.
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ovdje ćemo vidjeti crvenu točku i začuti klik.
01:19
So what we see
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Vidimo da
01:21
is that this neuron knows
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taj neuron zna
01:23
whenever the rat has gone into one particular place in its environment.
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je li štakor otišao na točno određeno mjesto u okolini.
01:26
And it signals to the rest of the brain
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I šalje signal ostatku mozga
01:28
by sending a little electrical spike.
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tim jednim električnim impulsom.
01:31
So we could show the firing rate of that neuron
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Dakle, možemo prikazati jačinu tog impulsa
01:34
as a function of the animal's location.
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kao funkciju lokacije životinje.
01:36
And if we record from lots of different neurons,
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I ako snimimo aktivnost više neurona,
01:38
we'll see that different neurons fire
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vidjet ćemo da različiti neuroni šalju impulse
01:40
when the animal goes in different parts of its environment,
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kako životinja ide u različite dijelove okoline,
01:42
like in this square box shown here.
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kao u ovom kvadratiću ovdje.
01:44
So together they form a map
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Zajedno, oni čine mapu
01:46
for the rest of the brain,
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za ostatak mozga,
01:48
telling the brain continually,
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neprekidno govoreći mozgu,
01:50
"Where am I now within my environment?"
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“Gdje se sada nalazim unutar moje okoline?”
01:52
Place cells are also being recorded in humans.
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Aktivnost stanica zaduženih za lociranje također je snimana i kod ljudi.
01:55
So epilepsy patients sometimes need
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Osobe koje boluju od epilepsije katkada trebaju
01:57
the electrical activity in their brain monitoring.
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električnu aktivnost pri nadziranju moždanih funkcija.
02:00
And some of these patients played a video game
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Neki od njih su igrali video igricu
02:02
where they drive around a small town.
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u kojoj voze auto po malenom gradiću.
02:04
And place cells in their hippocampi would fire, become active,
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Stanice njihovog hipokampusa bi odaslale impuls, aktivirale se
02:07
start sending electrical impulses
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i slale signal
02:10
whenever they drove through a particular location in that town.
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kad god bi oni provezli auto kroz točno određeno mjesto u tom gradiću.
02:13
So how does a place cell know
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Kako stanica za lociranje zna
02:15
where the rat or person is within its environment?
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gdje se štakor ili osoba nalaze?
02:18
Well these two cells here
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Ove dvije stanice ovdje
02:20
show us that the boundaries of the environment
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pokazuju nam da su granice okoline
02:22
are particularly important.
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osobito važne.
02:24
So the one on the top
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Ova gornja
02:26
likes to fire sort of midway between the walls
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voli slati signal s polovice puta između zidova
02:28
of the box that their rat's in.
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kutije u kojoj se štakor nalazi.
02:30
And when you expand the box, the firing location expands.
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A kada proširite kutiju, i preferirana lokacija za odašiljanje signala se proširi.
02:33
The one below likes to fire
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Donja stanica voli slati signal
02:35
whenever there's a wall close by to the south.
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uvijek kada postoji zid u blizini juga.
02:38
And if you put another wall inside the box,
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I ako postavite još jedan zid u kutiju,
02:40
then the cell fires in both place
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stanica će slati signal s oba mjesta,
02:42
wherever there's a wall to the south
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gdje god je zid u blizini juga,
02:44
as the animal explores around in its box.
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kako životinja bude istraživala oko kutije.
02:48
So this predicts
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Ovo ukazuje
02:50
that sensing the distances and directions of boundaries around you --
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kako je osjećaj za udaljenost i smjer u kojem se nalaze granice oko vas
02:52
extended buildings and so on --
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(u proširenom smislu zgrade itd.)
02:54
is particularly important for the hippocampus.
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povezan s hipokampusom.
02:57
And indeed, on the inputs to the hippocampus,
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I zaista, jedan od aferentnih putova za hipokampus,
02:59
cells are found which project into the hippocampus,
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stanice koje šalju projekcije u hipokampus,
03:01
which do respond exactly
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reagiraju upravo
03:03
to detecting boundaries or edges
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detektirajući granice i rubove
03:06
at particular distances and directions
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na posebnim udaljenostima i pravcima
03:08
from the rat or mouse
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od štakora ili miša
03:10
as it's exploring around.
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dok istražuje uokolo.
03:12
So the cell on the left, you can see,
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Stanica s lijeve strane, kao što vidite,
03:14
it fires whenever the animal gets near
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odašilje signal kada se životinja nađe kod
03:16
to a wall or a boundary to the east,
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zida ili granice blizu istoka,
03:19
whether it's the edge or the wall of a square box
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bio to ugao ili zid četvrtaste kutije,
03:22
or the circular wall of the circular box
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zaobljen zid okrugle kutije
03:24
or even the drop at the edge of a table, which the animals are running around.
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ili pak rub stola po kojem životinja hoda.
03:27
And the cell on the right there
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Stanica desno
03:29
fires whenever there's a boundary to the south,
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odašilje signal kada postoji granica prema jugu,
03:31
whether it's the drop at the edge of the table or a wall
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bio to rub stola
03:33
or even the gap between two tables that are pulled apart.
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ili mali prostor između dva spojena stola.
03:36
So that's one way in which we think
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Mislimo kako je to jedan od načina
03:38
place cells determine where the animal is as it's exploring around.
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na koji stanice za lociranje određuju gdje se životinja nalazi.
03:41
We can also test where we think objects are,
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Možemo testirati i osjećaj smještanja objekata u prostor,
03:44
like this goal flag, in simple environments --
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poput ove zastavice, u jednostavnim uvjetima,
03:47
or indeed, where your car would be.
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tj. gdje bi se mogao nalaziti vaš auto.
03:49
So we can have people explore an environment
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Na početku imamo ispitanike koji promatraju okolinu
03:52
and see the location they have to remember.
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i lokaciju koju moraju upamtiti.
03:55
And then, if we put them back in the environment,
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Kada ih poslije vratimo u istu okolinu,
03:57
generally they're quite good at putting a marker down
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generalno su prilično dobri u smještanju oznake
03:59
where they thought that flag or their car was.
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na mjesto na kojem je prije bila zastavica ili auto.
04:02
But on some trials,
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Možemo mijenjati
04:04
we could change the shape and size of the environment
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oblik i veličinu okoline
04:06
like we did with the place cell.
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kao što smo radili sa stanicama za lociranje.
04:08
In that case, we can see
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U tom slučaju, vidjet ćemo
04:10
how where they think the flag had been changes
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da se njihovo mišljenje o tome gdje je zastavica bila mijenja
04:13
as a function of how you change the shape and size of the environment.
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ovisno o promjeni oblika i veličine okoline.
04:16
And what you see, for example,
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Na primjer,
04:18
if the flag was where that cross was in a small square environment,
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ako je zastavica bila gdje se nalazi križić u maloj četvrtastoj okolini
04:21
and then if you ask people where it was,
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i pitamo ljude gdje je bila,
04:23
but you've made the environment bigger,
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ali povećamo okolinu –
04:25
where they think the flag had been
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njihova predodžba o mjestu na kojem se zastavica nalazila
04:27
stretches out in exactly the same way
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se proširuje isto kao što se proširilo
04:29
that the place cell firing stretched out.
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i područje na kojem stanice za lociranje odašilju impuls.
04:31
It's as if you remember where the flag was
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Čini se da pamtimo gdje se zastavica nalazila
04:33
by storing the pattern of firing across all of your place cells
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pohranjujući uzorke odašiljanja impulsa svih stanica
04:36
at that location,
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za lociranje na toj lokaciji.
04:38
and then you can get back to that location
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Možemo se vratiti na tu lokaciju
04:40
by moving around
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kružeći uokolo
04:42
so that you best match the current pattern of firing of your place cells
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tako što ćemo povezati trenutne uzorke odašiljanja impulsa stanica za lociranje
04:44
with that stored pattern.
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sa onima koje smo pohranili.
04:46
That guides you back to the location that you want to remember.
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To nas vodi natrag k lokaciji koju trebamo upamtiti.
04:49
But we also know where we are through movement.
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Ali također znamo gdje se nalazimo kroz pokret.
04:52
So if we take some outbound path --
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Ako krenemo nekim izlaznim putem,
04:54
perhaps we park and we wander off --
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na primjer parkiramo i odlutamo,
04:56
we know because our own movements,
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sjećamo se svojih pokreta,
04:58
which we can integrate over this path
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možemo ih ponovno ugrubo integrirati
05:00
roughly what the heading direction is to go back.
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te pronaći put natrag.
05:02
And place cells also get this kind of path integration input
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Stanice za lociranje također dobivaju projekciju tog tipa
05:06
from a kind of cell called a grid cell.
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od tzv. rešetkastih stanica.
05:09
Now grid cells are found, again,
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Rešetkaste stanice pojavljuju se
05:11
on the inputs to the hippocampus,
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kao projekcija u hipokampusu
05:13
and they're a bit like place cells.
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i nalik su stanicama za lociranje.
05:15
But now as the rat explores around,
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Kako štakor istražuje okolinu,
05:17
each individual cell fires
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svaka individualna stanica ispaljuje
05:19
in a whole array of different locations
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na nizu različitih lokacija
05:22
which are laid out across the environment
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koje su posložene
05:24
in an amazingly regular triangular grid.
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u nevjerojatno pravilan trokutast oblik.
05:29
And if you record from several grid cells --
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I ako snimimo aktivnost više različitih rešetkastih stanica –
05:32
shown here in different colors --
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što vidimo ovdje prikazano različitim bojama –
05:34
each one has a grid-like firing pattern across the environment,
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svaka ima uzorak nalik rešetki uzduž okoline,
05:37
and each cell's grid-like firing pattern is shifted slightly
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i svaki taj uzorak je malo pomaknut
05:40
relative to the other cells.
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u odnosu na uzorke ostalih stanica.
05:42
So the red one fires on this grid
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Crvena formira ovu rešetku,
05:44
and the green one on this one and the blue on on this one.
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zelena ovu, a plava ovu.
05:47
So together, it's as if the rat
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Dakle, to je kao da štakor
05:50
can put a virtual grid of firing locations
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na temelju svoje okoline sastavlja virtualnu rešetku lokacija
05:52
across its environment --
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na kojima se odašilje impuls –
05:54
a bit like the latitude and longitude lines that you'd find on a map,
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nešto poput okomitih i vodoravnih linija koje možete naći na karti,
05:57
but using triangles.
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samo koristi trokute.
05:59
And as it moves around,
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Kako se kreće uokolo,
06:01
the electrical activity can pass
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električna aktivnost prelazi
06:03
from one of these cells to the next cell
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s jedne na drugu stanicu
06:05
to keep track of where it is,
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i bilježi gdje se štakor nalazi,
06:07
so that it can use its own movements
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tako da on može znati gdje se nalazi
06:09
to know where it is in its environment.
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koristeći vlastite kretnje.
06:11
Do people have grid cells?
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Imaju li ljudi rešetkaste stanice?
06:13
Well because all of the grid-like firing patterns
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Budući da svi rešetkasti uzorci impulsa
06:15
have the same axes of symmetry,
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imaju iste osi simetrije,
06:17
the same orientations of grid, shown in orange here,
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istu orijentaciju rešetki, što je prikazano ovdje narančasto,
06:20
it means that the net activity
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to bi značilo da mrežastu aktivnost
06:22
of all of the grid cells in a particular part of the brain
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svih rešetkastih stanica određenog dijela mozga
06:25
should change
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možemo mijenjati
06:27
according to whether we're running along these six directions
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ovisno o tome krećemo li se uzduž jednog od ovih šest pravaca
06:29
or running along one of the six directions in between.
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ili jednog od šest pravaca između.
06:32
So we can put people in an MRI scanner
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Ljude možemo podvrgnuti MRI skeniranju
06:34
and have them do a little video game
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dok igraju video igru
06:36
like the one I showed you
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poput one koju sam vam pokazao.
06:38
and look for this signal.
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i tražiti taj signal.
06:40
And indeed, you do see it in the human entorhinal cortex,
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I zaista, taj signal možete vidjeti u ljudskom entorinalnom korteksu,
06:43
which is the same part of the brain that you see grid cells in rats.
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koji se nalazi na istom dijelu mozga na kojem kod štakora nalazimo rešetkaste stanice.
06:46
So back to Homer.
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Vratimo se Homeru.
06:48
He's probably remembering where his car was
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Vjerojatno se sjeća gdje mu se nalazi auto
06:50
in terms of the distances and directions
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u smislu udaljenosti te pravca
06:52
to extended buildings and boundaries
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zgrada i granica
06:54
around the location where he parked.
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koje okružuju mjesto na kojemu je parkirao.
06:56
And that would be represented
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I to bismo vidjeli kao odašiljanje signala
06:58
by the firing of boundary-detecting cells.
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stanica koje detektiraju granice.
07:00
He's also remembering the path he took out of the car park,
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Također, sjeća se i puta kojim je krenuo s parkirališta,
07:03
which would be represented in the firing of grid cells.
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a to bismo vidjeli kao odašiljanje signala rešetkastih stanica.
07:06
Now both of these kinds of cells
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Obje vrste stanica
07:08
can make the place cells fire.
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mogu dovesti do odašiljanja signala iz stanica za lociranje.
07:10
And he can return to the location where he parked
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Homer se može vratiti do mjesta gdje se parkirao
07:12
by moving so as to find where it is
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tražeći mjesto na kojem se
07:15
that best matches the firing pattern
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trenutno odašiljanje stanica za lociranje
07:17
of the place cells in his brain currently
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najbolje poklapa
07:19
with the stored pattern where he parked his car.
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s upamćenim uzorkom odašiljanja signala.
07:22
And that guides him back to that location
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To ga vodi natrag na lokaciju
07:24
irrespective of visual cues
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bez obzira na vizualne znakove
07:26
like whether his car's actually there.
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poput toga je li njegov auto zbilja tamo.
07:28
Maybe it's been towed.
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Možda ga je pauk odnio.
07:30
But he knows where it was, so he knows to go and get it.
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Ali on zna gdje je bio, tako da zna i otići po njega.
07:33
So beyond spatial memory,
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S druge strane,
07:35
if we look for this grid-like firing pattern
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ako pogledamo ove rešetkaste uzorke
07:37
throughout the whole brain,
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odašiljanja impulsa kroz cijeli mozak,
07:39
we see it in a whole series of locations
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vidimo serije lokacija
07:42
which are always active
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koje su aktivne uvijek
07:44
when we do all kinds of autobiographical memory tasks,
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kada obavljamo razne zadatke vezane uz autobiografsko sjećanje,
07:46
like remembering the last time you went to a wedding, for example.
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na primjer prisjećanje kada smo zadnji put bili na vjenčanju.
07:49
So it may be that the neural mechanisms
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Moguće je da se neuralni mehanizmi
07:51
for representing the space around us
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za prikazivanje prostora oko nas
07:54
are also used for generating visual imagery
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koriste ujedno i za generiranje vizualnih slika
07:58
so that we can recreate the spatial scene, at least,
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kako bismo mogli stvoriti prostorni prizor
08:01
of the events that have happened to us when we want to imagine them.
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događaja koji su nam se dogodili kada ih se želimo prisjetiti.
08:04
So if this was happening,
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Ako se to događa na taj način,
08:06
your memories could start by place cells activating each other
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prisjećanje počinje tako što se stanice za lociranje međusobno aktiviraju
08:09
via these dense interconnections
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putem gustih komunikacija,
08:11
and then reactivating boundary cells
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reaktiviraju stanice za detektiranje granica
08:13
to create the spatial structure
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kako bi stvorile prostornu strukturu
08:15
of the scene around your viewpoint.
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prizora s vaše točke gledišta.
08:17
And grid cells could move this viewpoint through that space.
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Rešetkaste stanice pomiču tu točku gledišta kroz prostor.
08:19
Another kind of cell, head direction cells,
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Još jedna vrsta stanica
08:21
which I didn't mention yet,
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koju dosad nisam spominjao,
08:23
they fire like a compass according to which way you're facing.
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stanice koje određuju smjer gibanja glave odašilju impulse poput kompasa ovisno o tome na koju stranu ste okrenuti.
08:26
They could define the viewing direction
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One definiraju pravac gledanja
08:28
from which you want to generate an image for your visual imagery,
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s kojeg želite generirati imaginarnu sliku,
08:31
so you can imagine what happened when you were at this wedding, for example.
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tako da na primjer, možete zamisliti što se događalo kada ste bili na tom vjenčanju.
08:34
So this is just one example
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Ovo je još jedan dokaz
08:36
of a new era really
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o novom dobu
08:38
in cognitive neuroscience
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koje je nastupilo u neuroznanosti,
08:40
where we're beginning to understand
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gdje počinjemo shvaćati
08:42
psychological processes
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psihičke procese
08:44
like how you remember or imagine or even think
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poput toga kako se prisjećamo, kako zamišljamo ili mislimo
08:47
in terms of the actions
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u okvirima aktivnosti
08:49
of the billions of individual neurons that make up our brains.
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milijardi individualnih neurona koji sačinjavaju naš mozak.
08:52
Thank you very much.
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Hvala puno.
08:54
(Applause)
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(Pljesak)
ABOUT THE SPEAKER
Neil Burgess - NeuroscientistAt University College in London, Neil Burgess researches how patterns of electrical activity in brain cells guide us through space.
Why you should listen
Neil Burgessis is deputy director of the Institute of Cognitive Neuroscience at University College London, where he investigates of the role of the hippocampus in spatial navigation and episodic memory. His research is directed at answering questions such as: How are locations represented, stored and used in the brain? What processes and which parts of the brain are involved in remembering the spatial and temporal context of everyday events, and in finding one's way about?
To explore this space, he and his team use a range of methods for gathering data, including pioneering uses of virtual reality, as well as computational modelling and electrophysiological analysis of the function of hippocampal neurons in the rat, functional imaging of human navigation, and neuropsychological experiments on spatial and episodic memory.
A parallel interest: Investigating our human short-term memory for serial order, or how we know our 123s.
Neil Burgess | Speaker | TED.com