Norman Swan: Babies' brains are highly plastic, meaning they're constantly adapting as they learn and respond to the world and the people around them.

It's now known that our brains as adults can change too, but are far less plastic than very young children's. The challenge is to find ways of unlocking this plasticity when it's needed, say if we've had a brain injury.

According to other Canadian research, video games may be one way. Daphne Maurer is director of the Visual Development Laboratory at McMaster University in Hamilton Ontario. She has found clues to when plasticity might be locked off in babies and how in some adults it actually may persist unbeknownst to them.

Daphne Maurer: We're talking about the beginning of development when the brain is getting tuned to the environment in which the child has been born. So the child is learning 'my people talk that language, my people look like that, my people eat this kind of food'. So the early brain plasticity, the baby's brain starts with an exuberance of connections, it's choosing to reinforce those that match the cultural environment, and those that don't match get pruned away. And that's what we call critical periods, periods during which the child must hear language, must have vision, must be exposed to foods in order for that stabilisation to the environment to occur.

Norman Swan: So in a sense they go for everything and then they have to edit.

Daphne Maurer: Exactly. Instead of being born with connections that process exactly what we need to process in our lives, we're born with this process of tuning by experience. But when we talk about brain plasticity we're talking about something more in the last five years because we have discovered that there are brakes on plasticity. The brain has to work really hard not to be plastic, and that has allowed us to discover ways to renew plasticity in the adult brain.

Norman Swan: You'd think the brain would want to stay plastic. Why does it stop being plastic?

Daphne Maurer: Part of the end of plasticity is a brain that is well matched to the environment of that child.

Norman Swan: Lock that all in.

Daphne Maurer: Right. And we now have emerging evidence from animal models that part of what may go wrong in a number of mental and neurological diseases is that these brakes are not put on as strongly as is normal.

Norman Swan: And of course, paradoxically, later in life if something goes wrong you want that plasticity to come back.

Daphne Maurer: Yes, you want the plasticity if you have a stroke, if you have a detached retina that's reattached, if something goes wrong with your sensory or cognitive systems. And what we have learned is the brain is still plastic in adulthood. There do seem to be ways to take off the brakes and to restore plasticity in adulthood.

Norman Swan: So tell me about the remarkable findings you've made in adults who are blind who get their sight back.

Daphne Maurer: We've studied children who had a period of temporary blindness. So these are children who are born with a very rare condition where they have dense cataracts in both eyes. And what that means is during the first two to three months of life until the cataracts are removed surgically and they are given contact lenses they are getting no experience of beginning to learn the structure of the world. Even though the child with normal eyes, the normal newborn, sleeps most of the time, has really bad vision, can only see large things of high contrast, the children who miss that because of cataracts end up with a long list of seemingly permanent deficits, including lower acuity than normal.

Norman Swan: In other words they can't see as well.

Daphne Maurer: They can't see as well. So we wondered what could we do when they were 20 to 30 years old and the brain is not supposed to be plastic anymore. And we've had these adults who had seemingly permanent deficits play a first-person shooter game for 40 hours over four weeks.

Norman Swan: Videogames.

Daphne Maurer: Videogames, because there is evidence that adults with normal eyes when they play an action videogame, particularly a first-person shooter, improve their vision. And we tried it with these adults we had followed for 25 years who have seemingly permanent visual deficits, and lo and behold their vision improved, including their visual acuity.

Norman Swan: Really?

Daphne Maurer: Really.

Norman Swan: So this is from sitting at a videogame firing a gun?

Daphne Maurer: Right, two hours a day, 40 hours total, and there was an improvement in vision. Typically they could read one to two lines further down the letter chart. This was only a 40 hour intervention, so we have no reason to believe that this is the limit of what could be achieved.

Norman Swan: What's going on?

Daphne Maurer: That's a really good question. There are really three possibilities, and this is the next stage of the research. One possibility is the brain is actually being rewired, that new connections are being formed. And we know that can happen after stroke. So that's a real possibility. Another possibility is that there were connections there but they were sub-threshold, they couldn't be activated, and so that what we've done is unmask existing connections. And we know from the literature that can happen. And the third possibility of what's going on in videogames is what we call improved efficiency. So…

Norman Swan: Making the most of what you've got.

Daphne Maurer: Making the most of what you've got, exactly. It's like listening to a radio program where you don't quite have the channel tuned in properly. So you can hear the signal but there's a lot of static. And maybe what we're teaching these patients to do is to be better at hearing that signal, even though it's so weak and there's so much static.

Norman Swan: Does the effect wear off?

Daphne Maurer: We would be really surprised if it wears off, because they have better vision, and that vision is going to be reinforced in everyday life.

Norman Swan: Now, you've also been studying this in adults with synaesthesia—this is fascinating. Describe synaesthesia.

Daphne Maurer: In adults with synaesthesia, stimulation of one sensory modality—let's say hearing—causes something extra, typically the perception of colour. So we say…

Norman Swan: You hear colours…

Daphne Maurer: You hear colours. C sharp might be vermillion and D flat might be turquoise. And it can be across any of our sensory systems, so some people taste words. Some people, it's just within one sensory modality, so when they see black letters they perceive colour.

Norman Swan: Some people when they think of numbers they see them in patterns.

Daphne Maurer: They see them in space. So someone might tell you January is here, February is there, March is behind my back.

Norman Swan: That's me…

Daphne Maurer: You have spatial-sequence synaesthesia? That's fascinating. I envy you. People with synaesthesia usually feel sorry for those of us who don't have it, and they don't want to be cured. Now, the reason I'm looking at synaesthesia is because studies suggest the reason people are synesthetic is that the brain remained in a slightly more infantile state.

Norman Swan: You're not the first person to say that.

Daphne Maurer: And what we think happens in synaesthesia is that the pruning is incomplete. So I've been looking at synaesthesia because it gives me clues to what's going in in the perception of young children. And so far we've done some tests and they've all proved to be correct. So one thing that synesthetes who have coloured letters report, they pretty much agree that Cs are yellow, Xs are black, Os are white.

Norman Swan: So this is across the board.

Daphne Maurer: Yes. Even though there are a lot of idiosyncrasies, they do agree on certain colour-letter combinations. And when we test for those in toddlers, they show exactly the same associations. So…

Norman Swan: So before the toddlers start to prune, they're synesthetic.

Daphne Maurer: That seems to be the case. We've also worked out a characteristic of coloured hearing. Again, C sharp might be vermillion for one synesthete but turquoise for another synesthete. But they agree that as the pitch gets higher, the colours get lighter. And we tested for that in toddlers, and they agreed. We had two balls going down the screen, one white, one black. There was a higher pitch and a lower pitch. We played the pitch, we said 'Which ball is making that sound?' And they said the higher pitched sound was coming from the white ball and the lower pitched sound was coming from the black ball.

Norman Swan: Does this have any practical implications?

Daphne Maurer: It might have implications for education, to the extent that young children's perception is different from adults' perception. Some of the ways we teach may be confusing or more likely there may be things one could use to facilitate learning. For example, presenting Cs in yellow. If that seems like a natural combination to young children, they might have an easier time learning that letter of the alphabet if they were taught it first in yellow.

Norman Swan: Have you found an age where synaesthesia is lost?

Daphne Maurer: Probably never. There is underground synaesthesia in all of us. If I ask adults to make connections between pitch and surface lightness, or if I ask them to make connections between letters and colours, our colour associations exactly match the toddlers and the synesthetes. So the pruning is incomplete in everyone, not just in synesthetes. But in those of us without synaesthesia it's been sufficient that the synaesthesia doesn't get to the conscious perception.

Norman Swan: And is there any evidence that adults who are synesthetic have more plastic brains?

Daphne Maurer: That is an excellent question and we just started testing that in my lab. We are comparing adults with and without synaesthesia, seeing if maybe they are better at discriminating between monkey faces. We know that young infants are very good at discriminating between monkey faces. They discriminate them as well as human faces. But by the end of the first year of life they've gotten better for humans and worse for monkeys. So we're testing them on their ability to discriminate between monkey faces and between non-native speech sounds—predicting that either they will make the discriminations even as adults, or they'll be easily retrained to make those discriminations.

Norman Swan: And you'll just have to wait for the results.

Daphne Maurer is director of the Visual Development Laboratory at McMaster University in Hamilton, Ontario.