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Updated: September 29, 2011 09:08 IST

New light shed on how memory is organised

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A model of the human brain aboard the Science Express. File photo
The Hindu
A model of the human brain aboard the Science Express. File photo

A method that allowed measurements right down to the millisecond level was used

In an article published today (September 29) in Nature, researchers describe exactly how the brain reacts during the transition between one memory and the next.

Consider these situations: You're rudely awakened by the phone. Your room is pitch black.

It's unsettling, because you're a little uncertain about where you are — and then you remember. You're in a hotel room.

Similar disorientation

Sound like a familiar experience? Or maybe you've felt a similar kind of disorientation when you walk out of an elevator onto the wrong floor?

But what actually happens inside your head when you experience moments like these?

The study by researchers at the Norwegian University of Science and Technology's Kavli Institute for Systems Neuroscience employed a method that allowed them to make measurements right down to the millisecond level.

The research was conducted in the laboratory of May-Britt and Edvard Moser, co-director and director respectively of NTNU's Kavli Institute, by first author Karel Jezek.

Their findings show that memory is divided into discrete individual packets, analogous to the way that light is divided up into individual bits called quanta. Each memory is just 125 milliseconds long — which means the brain can swap between different memories as often as eight times in one second, according to a Norwegian University of Science and Technology press release.

“The brain won't let itself get confused,” says Professor May-Britt Moser. “It never mixes different places and memories together, even though you might perceive it that way.

This is because the processes taking place inside your head when your brain is looking for a map of where you are take place so fast that you don't notice that you are actually switching between different maps. When you feel a little confused, it is because there is a competition in your brain between two memories. Or maybe more than two.”

Brain researchers Edvard and May-Britt Moser are trying to understand exactly how the brain works. Their approach is to meticulously monitor electrical activity in different parts of the rat brain, while the rats explore different mazes.

Painstaking approach

It's a painstaking approach that provides them ever more pieces to the puzzle that is the workings of the brain.

To explore the question of whether the brain mixes memories together, the researchers created a special box for their laboratory animals that effectively enabled them to instantaneously ‘teleport' a rat from one place to another — without the help of the Starship Enterprise as featured in the science fiction teleseries ‘Star Trek.'

Then, they tested how the brain handled the memory of place when the experience of that place suddenly changed from one location to another.

“We tricked the rats,” May-Britt Moser explains. “They're not really teleported of course, but we have an approach that makes them believe that they have been. The features of the box, which give the rats a sense of where they are, are actually ‘constructed' out of different lighting schemes. So we can switch from one group of location characteristics to another with the flick of a light switch.”

The rats were trained over a long time to believe that the various lighting schemes represented different rooms. The researchers can tell that the rats truly believe that they are in different places because of their brain activity.

Specific activity pattern

“Once we turn on one lighting scheme, we can read a very specific pattern of activity in the cells in the part of the rat's brain that creates maps,” May Britt Moser says. “And when we switch to the other lighting scheme, the map pattern in the brain is completely different.”

When the researchers ‘teleport' the rats from one place to another by flipping the light switch from A to B, the rats experience exactly the kind of confusion you feel when you momentarily don't know where you are.

“But the mind doesn't actually mix up the maps," she says. "It switches back and forth between the two maps that represent rooms A and B, but it is never in an intermediate position. The brain can 'flip' back and forth between the two different maps, but it is always either or, site A or site B.”

May-Britt and Edvard Moser have previously discovered the location of the brain's sense of place, shown how the brain works to make memories distinctively different, and have found that the brain has a mechanism to switch between experiences through the use of senses and images stored as memories.

Now the researchers have also shown how the brain switches between individual memories, and how long the brain lingers on the different bits of memory. “We are beginning to get a glimpse of the contours of the mechanisms that make up the world of our thoughts,” says May-Britt Moser.

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Nice article. Human brain could be modelled using state space control theory. Parts of the memory needed for the survival are bright when the body is in active state and are updated based on the real-world events. But. when I go to sleep I sometime realize that the dreams from the last night begin to continue like a serial, which I seldom remember after I woke up. So the dream state memory is activated during sleep. Dreams are virtual life which is a different state. Confusing yet interesting !!

from:  Pothikan Suresh
Posted on: Sep 30, 2011 at 11:22 IST

Confusion in perception causes giddiness, and syncope. When one sees multiple images moving in different directions one feels giddiness, and it affects the rhythm of blood flow to the brain. Imagine you are entering an ATM booth. The glass door presents an image of moving objects behind you, which is already reversed. You also see through the plain glass and find some other image reflected from inside shining objects, or moving men. As you push the door the angle of reflection also shifts. You also see the actual stationary things. The result is there are at least three different images falling on the retina. This the mind is unable to sort out or accept.
A similar exprience can be had when you are seated in a bus which has tinted glass for windows. The right side images get reflected on left panes, while you also see the objects outside the glass. This causes confusion. The driver also suffers when he has to look at things in front, look at the RV & wing mirrors. Hence syncope.

from:  Prof.M.D.Jayabalan
Posted on: Sep 30, 2011 at 07:50 IST

pioneering stuff. a new think.

from:  karan
Posted on: Sep 30, 2011 at 07:47 IST

I would like to comment on two different aspects of brain functioning: one, swapping between two or more memory packets. two, the gap between "seeing" and "receiving and registering". The first one relates to absentmindedness. While you are doing something you suddenly remember that another thing must also be done at that time. You shift your action, and generally the first action is forgotten. The remedy to such absentmindedness is to 'allot' particular place for 'placing things back in position'. Most importantly concentrate on one action at a time. Ageing and using certain medications (BP control tablets) tend to weeken memories.
The second point is called 'paramnesia'. While your eyes turn round at different objects, like a camera the brain captures the scenes or faces without consciously observing. Again when you see the stranger or place you get the feeling that you had already seen him or been there. It is the twilight zone where thoughts of previous birth appears.

from:  Dr M.D.Jayabalan
Posted on: Sep 30, 2011 at 07:26 IST

sir,we thank you for the above information of how our brain works to react and tell us when we just awake and as we walk during day,etc! I am 80 yrs and my wife,jayalakshmi,73 yrs old, and thanks to Almighty, and good habits & vegetarian food,etc our memory is normal but still we have problems these days in recollecting near memories but old memories come fast as we get older? Our doctors advised us to take more leafy vegetables to help brain retain memory as our age advance.

from:  c.g.venkatesan
Posted on: Sep 29, 2011 at 20:53 IST

the research finding has thrown some light on the contentious issue of structure of brain which was explained by various schools of thought hitherto.Rats during their conditioning sessions try to encode some cues along with the stimulus material which they will further use while retrieving the learned material which can be objects, events or persons.confusion occurs in the subjects regarding their location if the retrieval cues they use do not match the question posed or when there is a contention between various packets of stimulus material that is encoded in long term memory.sometimes the cues undergoes decay when they are not put in to use.the rats may fall into dilemma when they are put into altogether a different kind of maze where they need to reconstruct their schema of events in order to suit their question and then retrieve the appropriate response.

from:  AVINASH
Posted on: Sep 29, 2011 at 17:57 IST

An amazing research to prove how our brain actually works and one of the most important highlighted point in this article is that the brains memory power increases if situations are stored in it in the form of photos.

from:  Nitesh verma
Posted on: Sep 29, 2011 at 17:51 IST

The research seems interesting but what I don't understand with these kind of articles is, how can you separate brain from consciousness? If I understood correctly, the article says, you 'feel' 'confused' because the brain is 'switching between memory locations'. If the brain is switching and 'you' are getting confused, then who are 'you'. I think consciousness goes hand-in-hand(is a part of) with brain,doesn't it? It doesn't make sense to differentiate the two. Also never compare working of brain in our digital logic terms...

from:  manav
Posted on: Sep 29, 2011 at 17:19 IST

knowing about the working of the human brain-which is more like a 100 core processor; we can develop fastest ,most efficient & intelligent technology.

from:  Nakul Singh Rawat
Posted on: Sep 29, 2011 at 10:47 IST

I fully agree with the results of the research reg. the pockets of each smallest pieces of memory in the brain. some times the recent event can not be memorised and some times the memory gathered decades ago gets refreshed in a fraction of a second. Few years back, I could recite the holy sermons orally comprised of more tahn 22000 words or 99000 characters at the age of 55 years. Now because of liquir habit some pockets of memory have become dim or confused. One more thing I observed is that memory increases by testing it on daily basis. Without such testing nothing is memorised even if we read it hundreds of times

from:  DR. J S BHATTI
Posted on: Sep 29, 2011 at 10:45 IST
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