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Current time:0:00Total duration:10:34

Emotions: cerebral hemispheres and prefrontal cortex

Video transcript

so what we have here is a brain and this is like we're above the person looking down into their brain to orient you let me draw two eyes here and this is the front of the brain and this is the back of the brain and we're looking at it like I said from the top now why are we looking at a brain well I want to talk about a certain area of the brain known as the cerebral cortex and how it plays a role in emotions and there's a number of different ways that you can divide up the cerebral cortex and organize it so we're going to look at a few in terms of emotion so one way that you can view the brain is in terms of hemispheres and in your brain you have two hemispheres you have a left hemisphere and a right hemisphere and the way you think of hemispheres it's as if you've drawn a line down the brain and you can split into two different hemispheres you have the left hemisphere in the right hemisphere and there's actually some differences between the left and right hemisphere researchers actually found that positive emotions evoked more electrical activity on the left side of the brain than on the right whereas negative emotions tend to elicit more activity in the right hemisphere now you might be wondering how did they figure that out well what they did is they had participants in the research study watch a TV screen so let's draw a TV here this was several years ago so I bet TVs had bunny ears back then so we'll draw some bunny ears here so what this research study did was they had the participants watch films either evoked pleasure or disgust in pleasure films or things like the kind of videos that people share with each other on YouTube I mean obviously YouTube back then didn't exist so they just got films of things that evoked positive emotions like puppies playing and flower and I actually guerrilla taking a bath at the zoo which I I guess it does bring quite a bit of pleasure but I that wouldn't be the first thing that came to my mind and then they hadn't watched other videos that evoked feelings of disgust and these are like shock films like videos of third-degree burns and very like gory leg amputations things that would evoke negative emotions and while these participants were watching these films the researchers videotaped their facial expressions and also recorded their brain activity through something called an EEG recording and EEG recordings basically measure the electrical activity of your brain and what they found was that pleasure films increase activity in the left hemisphere because the pleasure films are associated with positive emotions now is not to say that there wasn't any activity in the right hemisphere there's just more activity in the left hemisphere because positive emotions increase activity in the left hemisphere and the same could be said for the disgusting shock films on EEG recording they found that participants had more activity in the right hemisphere these discussing films are more associated with negative emotions like fear and disgust so I think is pretty neat that while the brain such a complicated structure that you can actually just split it down the middle and think of it in terms of left and right so you can associate the left hemisphere with positive emotions in the right hemisphere with negative emotions but that's not all in terms of hemispheres this concept of left and right hemispheres becoming more active in certain situations can also be applied to social interaction and how outgoing and sociable you are and in a different study researchers observed a group of a four year olds playing in a group so I'm going to draw some little kids here so you have someone here the researchers watched the kids interacting in groups and saw how they interact with each other so here two guys and there you can see them sharing a cool toy here and check out their expression they're smiling and it looks like they're having a great time and some kids that's how they act other kids tend to be more isolative some kids like to isolate a little bit more and be alone and here's an example here's one kid here he's just kind of sitting he's all alone he's frowning he's kind of isolating over here so after observing and noting how these children behaved they did a similar experiment to what we mentioned above and they took EEG recordings and noticed something kind of interesting that the kids who were more sociable playing in a group they tended to have an increased level of activity in their left hemisphere so I'll put a sociable on the other hand they notice that the children who isolated more like this guy here they tended to have more activity in the right hemisphere and to represent that I'll write isolative and of course there's been other studies as well and other research shows that people with more active left hemispheres they tend to be more interested joyful and enthusiastic about things whereas those with more active right hemispheres and to be more timid fearful avoidant and even depressed so that's a basic overview of emotions in terms of brain hemispheres another way you can look at the cerebral cortex is by dividing it into functional divisions so I'm going to erase these structures up here and some of these functional divisions you can already see in different colors here but the one that I want to focus on is the prefrontal cortex prefrontal cortex the prefrontal cortex is basically this area right here see area all the way in the front of your brain it's actually right behind your forehead and this area of the brain is responsible for many like high order functions like language information processing all the things that you think of that make humans humans the ability to solve math problems think through philosophical issues these sometimes these are referred to as very like cerebral activities and what do you think that term comes from well the cerebral cortex and the prefrontal cortex is a part of the cerebral cortex and like I said the prefrontal cortex is really what distinguishes humans and because of that is extremely well developed in humans and it undergoes the greatest amount of development after birth I mean think of how you become more mature as you get older or so they say in terms of the prefrontal cortex you use this part of the brain when you're trying to solve problems make decisions and manage how you behave in social situations for instance you probably behave differently during a job interview and you do during a wild sporting event and even if you don't you know that there are certain norms and expectations in job interviews then there are in sporting events and the ability I know that comes from your prefrontal cortex and I mention this because in another video we talked about the amygdala and the amygdala causes fear anxiety anger and aggression and I'm sure you've had the experience in your life where you felt very angry at someone and when you have those sorts of feelings you know maybe your primal reaction is to you know attack the person or physically hit them but of course many people don't do that and why is that well they because they have a well-developed prefrontal cortex and the ability to understand well you know violence isn't the answer you shouldn't attack someone no matter how you feel that thinking that you have in your mind where you say no no I should know no I would restrict my behavior I should you know walk away all those thoughts that you have come from the prefrontal cortex that helps them edge how you behave in social situations one question that's interesting to consider is what would happen if you damaged your prefrontal cortex how would you act well there's a famous example of this where someone actually did have that happen to them and his name was Phineas Gage a Phineas Gage was 25 years old back when it was 1848 he was a railroad worker selectroll some train tracks here and as part of building this railroad they had to do controlled explosions to make way for it in Phineas Gage was responsible for overseeing that so here he is and he was just overseen these explosions now during one of these explosions an iron rod was sent flying through the air and actually penetrated through his skull I went in one side and out the other and during its course through his skull it destroyed much of his prefrontal cortex the man that Phineas Gage was after the accident was not the same man he was before you see before his friends and co-workers knew him as a hard-working and well liked guy after he experienced this trauma to his head he became rude and gruff he swore a lot and just behaved inappropriately overall and that's because he no longer had a functioning prefrontal cortex so that's the cerebral cortex so if you ever wonder what makes a human human well a lot of it's actually right behind your forehead and the area known as the prefrontal cortex