[Music] [Music] [Applause] 15 years ago it was widely assumed that the vast majority of brain development takes place in the first few years of life back then 15 years ago we didn't have the ability to look inside the living human brain and Development Across the lifespan in the past decade or so mainly due to advances in brain imaging technology such as magnetic resonance imaging or MRI neuroscientists have started to look inside the living human brain of all ages and to track changes in brain structure and brain function so we use structural MRI if you like to take a snapshot a photograph at really high resolution of the inside of the living human brain and we can ask questions like how much gray matter does does the brain contain and how does that change with age and we also use functional MRI called fmri to take a video a movie of brain activity when participants are taking part in some kind of task like thinking or feeling or perceiving something so many labs around the world are involved in this kind of research and we now have a really rich and detailed picture of how the living human brain develops and this picture has radically changed the way we think about human brain development but by revealing that it's not all over in early childhood and instead the brain continues to develop right throughout adolescence and into the 20s and 30s so adolescence is defined as the period of life that starts with the biological hormonal physical changes of puberty and ends at the age at which an individual attains a stable independent role in society it can go on a long time one of the brain regions that changes most dramatically during adolescence is called prefrontal cortex so this is uh this is a model of the human brain and this is prefrontal cortex right at the front prefrontal cortex is an interesting brain area it's proportionally much bigger in humans than in any other species and it's involved in a whole range of high level cognitive functions things like decisionmaking planning planning what you're going to do tomorrow or next week or next year inhibiting inappropriate behav Behavior so stopping yourself saying something really rude or doing something really stupid it's also involved in social interaction understanding other people and self-awareness so MRI studies looking at the development of this region have shown that it really undergoes dramatic development during the period of adolescence so if you look at gry matter volume for example gry matter volume across age from Age 4 to 22 years increases during childhood which is what you can see on this graph it PE peaks in early adolescence the arrows indicate Peak gray matter volume in prefrontal cortex you can see that that Peak happens a couple of years later in boys relative to girls and that's probably because boys go through puberty a couple of years later than girls on average and then during adolescence there's a significant decline in gry matter volume in prefrontal cortex now that might sound bad but actually this is a really important developmental process because gray matter contains cell bodies and connections between cells the copses and this decline in gry matter volume during prefrontal cortex is thought to correspond to synaptic pruning the elimination of unwanted synapses this is a really important process it's partly dependent on the environment that the animal or the human is in in that synapses that are being used are strengthened and copses that aren't being used in that particular environment are pruned away you can think of it a bit like pruning a rose bush you prune away the weaker branches so that the remaining important branches can grow stronger and this process which effectively fine tunes brain tissue according to the species specific environment is happening in prefrontal cortex and in other brain regions During the period of human adolesence so a second line of inquiry that we use to track changes in the Adolescent brain is using functional MRI to look at changes in brain activity across age so I'll just give you an example from my lab so my lab we're interested in the social brain that is the network of brain regions that we use to understand other people and to interact with other people so I like to show a a photograph of a soccer game to illustrate two aspects of how your social brains work so this is a soccer game Michael Owen has just missed a goal and he's lying on the ground and the first aspect of the social brain that this picture really nicely illustrates is how automatic and instinctive social emotional responses are so within a split second of Mich Owen missing this goal everyone is doing the same thing with their arms and the same thing with their face even mik Owen as he slides along the grass is doing the same thing with his arms and presumably has a similar facial expression and the only people who don't are the guys in yellow at the back and I I think they're on the wrong end of the stadium and they're doing another social emotional response that we all instantly recognize and that's the second aspect of the social brain that this picture really nicely illustrates how good we are at reading other people Behavior their actions their gestures their facial expressions in terms of their underlying emotions and mental States so you don't have to ask any of these guys you have a pretty good idea of what they're feeling and thinking at this precise moment in time so that's what we're interested in looking at in my lab so we in my lab we bring adolescents and adults into the lab to have a brain scan we give them some kind of task that involves thinking about other people their minds their mental States their emotions and one of the findings that we've found several times now as have other labs around the world is part of the prefrontal cortex called medial prefrontal cortex which is shown in Blue on the slide and it's um right in the middle of prefrontal Cortex in the in the midline of your head this region is more active in adolescence when they make these social decisions and think about other people than it is in adults and this is actually a metaanalysis of nine different studies in this area from labs around the world and they all show the same thing that activity in this medial prefrontal cortex area decre increases during the period of adolescence and we think that might be because adolescents and adults use a different mental approach a different cognitive strategy to make social decisions and one way of looking at that is to do Behavioral Studies whereby we bring people into the lab and we give them some kind of Behavioral task and I'll just give you another example of the kind of task that we use in my lab so imagine that you're the participant in one of our experiments you come to the lab you see this computerized task in the this task you see a set of shelves now there are objects on these shelves on some of them and you'll notice there's a guy standing behind the set of shelves and there are some objects that he can't see they're occluded from his point of view with a kind of gray piece of wood this is the same set of shelves from his point of view notice that there are only some objects that he can see whereas there are many more objects that you can see now your task is to move objects around the director standing behind the set of shells is going to direct you to move objects around but remember he's not going to ask you to move objects that he can't see this introduces a really interesting condition whereby there's a kind of conflict between your perspective and the director's perspective so imagine he tells you to move the top truck left there are three trucks there you're going to instinctively go for the white truck cuz that's the top truck from your perspective but then you have to remember oh he can't see that truck so he must mean me to move the blue truck which is the top truck from his perspective now believe it or not normal healthy intelligent adults like you make errors about 50% of the time on that kind of trial they move the white truck instead of the blue truck so we give this kind of task to adolescents and adults and we also have a control condition where there's no director and instead we give people a rule we tell them okay we're going to do exactly the same thing but this time there's no director instead you've got to ignore objects with a dark gray background you'll see that this is exactly the same condition only in the no director condition they just have to remember to apply this somewhat arbitrary rule whereas in the director condition they have to remember to take into account the director's perspective in order to guide their ongoing Behavior okay so if I just show you the percentage errors in a large developmental study we did this is in a study ranging from age seven to adulthood and what you're going to see is a percentage errors in the adult group in both conditions so the gray is the direct dor condition and you see that our intelligent adults are making errors about 50% of the time whereas they make far fewer errors when there's no director present when they just have to remember that rule of ignoring the gray background developmentally these two conditions develop in exactly the same way between late childhood and midadolescence there's an improvement in other words a reduction of errors in both of these trials in both of these conditions but it's when you compare the last two groups the mid-adolescent group and the adult group where things get really interesting because there there is no continued Improvement in the no direct condition in other words everything you need to do to in order to remember the rule and apply it seems to be fully developed by mid-adolescence whereas in contrast if you look at the last two gray bars there's still a significant Improvement in the directed condition between midadolescence and adulthood and what this means is that the ability to take into account someone else's perspective in order to guide ongoing Behavior which is something by the way that we do in everyday life all the time time is still developing in mid to late adolescence so if you have a teenage son or a daughter and you think you sometimes think they have problems taking other people's perspectives you're right they do and this is why so we we sometimes um laugh about teenagers we they're parodied sometimes even demonized in the media for their kind of typical teenage Behavior they take risks they're sometimes Moody they're very self-conscious I have a really nice anecdote from a friend of mine who said that the thing he noticed most about his teenage daughters before and after puberty was their level of embarrassment in front of him so he said before puberty if my two daughters were messing around in a shop I'd say hey stop messing around and I'll sing your favorite song and instantly they'd stop messing around and he'd sing their favorite song after puberty that became the threat the very notion of their dad singing in public was enough to make them behave so people often ask well is adolescence a kind of recent phenomena is it something we've invented recently in the west and actually the answer is probably not there are lots of descriptions of adolescence in in history that sound very similar to the descriptions we Ed today so there's a famous uh quote by Shakespeare from the Winters Tale where he describes adolescence as follows I would there were no age between 10 and 3 and 20 or that youth would sleep out the rest for there's nothing in the between but getting wenches with child wronging the ancient tree stealing fighting he then goes on to say having said that would any but these boiled brains of 19 and 2 and20 hunt in this weather so almost 400 years ago Shakespeare was portraying Adolescence in a very similar light to the light that we portray them in today but today we try to understand their behavior in terms of the underlying changes that are going on in their brain so for example take risk-taking we know that adoles an are have a tendency to take risks they do they take more risks than children or adults and they are particularly prone to taking risks when they're with their friends there's a important drive to become independent from one's parents and to impress one's friends in adolescence but now we try to understand that in terms of the development of a part of their brain called the lyic system so I'm going to show you the lyic system in red in the slide behind me and also on this brain so the lyic system is Right deep inside the brain and it's involved in things like emotion processing and reward processing it gives you the rewarding feeling out of doing fun things including taking risks it gives you the kick out of taking risks and this region the the regions within the lyic system have been found to be hyper sensitive to the rewarding feeling of risk-taking in adolescents compared with adults and at the very same time the prefrontal cortex which you can see in blue in the slide here which stops us taking excessive risks is still very much in development in adolescence so brain research has shown that the Adolescent brain undergoes really quite profound development and this has implications for education for rehabilitation and intervention the environment including teaching can and does shape the developing adolescent brain and yet it's only relatively recently that we have been routinely educating teenagers in the west all four of my grandparents for examp example left school in their early adolescence they had no choice and that's still the case for many many teenagers around the world today 40% of teenagers don't have access to secondary school education and yet this is a period of life where the brain is particularly adaptable and malleable it's a fantastic opportunity for Learning and creativity so what's sometimes seen as the problem with adolescence heightened risk-taking poor impul s control self-consciousness shouldn't be stigmatized it actually reflects changes in the brain that provide an excellent opportunity for education and Social Development thank [Applause] [Music] [Applause] [Music] [Applause] you