In this video I describe two early studies looking at the role of brain structures in emotion processing; work by Heinrich Kluver & Paul Bucy, and James Olds & Peter Milner. These studies helped to identify the role of structures in the limbic system (the hypothalamus and amygdala) which are involved in motivation and emotional appraisal.
Don’t forget to subscribe to the channel to see future videos! Have questions or topics you’d like to see covered in a future video? Let me know by commenting or sending me an email!
Check out my book, Master Introductory Psychology, an alternative to a traditional textbook: http://amzn.to/2eTqm5s
Video Transcript
Hi, I’m Michael Corayer and this is Psych Exam Review. In this video we’re going to talk about emotions in the brain and we’ll start with some research by Heinrich Kluver and Paul Bucy. And what Kluver and Bucy did was they removed the temporal lobes of rhesus monkeys and when they did this they found that the monkeys showed a certain pattern of symptoms; and one of these symptoms was that they would attempt to eat inedible items. They would put just about anything in their mouths and this is called hyperphagia. And the monkeys also became hypersexual so they would attempt to mate, not just with other rhesus monkeys, but with other species or even with inanimate objects. Lastly, the monkeys became incredibly docile; they no longer showed fear when they were handled by the researchers. In fact they didn’t even show fear in the presence of snakes.
So here’s a picture of Heinrich Kluver and Paul Bucy here and I should mention that this pattern of symptoms is referred to as Kluver-Bucy syndrome. And here we can see a cat demonstrating one of these symptoms of Kluver-Bucy syndrome; it’s attempting to mate with a number of other species. And here we can see a kangaroo demonstrating the same. You might think that because Kluver and Bucy surgically removed the temporal lobes, that the temporal lobes must be involved in these symptoms. So it must be the case that the temporal lobes are involved in regulating eating behavior, or sexual behavior, or fear. But that’s actually not the case. It turns out the removal of the temporal lobes also damaged other areas of the brain and these are the areas that are more directly related to the symptoms. And these are areas that make up what’s called the limbic system.
And so in order to understand these areas of the limbic system that are involved in these symptoms, we’re going to look at some research conducted in the 1950s by James Olds and Peter Milner.
What Olds and Milner did was they surgically implanted electrodes into the brains of rats and these electrodes were then connected to a lever so the rat could self-administer electrical stimulation to this area of the brain that the electrode was connected to. And so what Olds and Milner wanted to see was, which areas of the brain would the rat be motivated to stimulate and which areas would not be so motivating? So there were areas of the brain they connected the electrode to, where they found the rat would avoid pressing the lever, but there were areas that the rat would be motivated to press the lever. This indicated that it was pleasurable or rewarding to the rat to receive stimulation to that area. And so one of these areas was the septal area of the rat’s brain; where they found that the rat would press the lever in order to receive stimulation of this area.
And in later research they found an area of the hypothalamus called the nucleus accumbens and this area was particularly rewarding for the rats because the rats would press the lever continuously. They would just press and press. They would even ignore food or the possibility of mating or sleep in order to press the lever. They would essentially press it until they passed out from exhaustion. So this indicated that this area of the brain in the hypothalamus was particularly important for understanding these rewarding activities like eating and sex.
And so here we can see one of Olds and Milner’s rats; you can see this wire here is going to the electrode that’s been implanted into the rat’s brain. And so when the rat presses this lever here, he receives some stimulation of that brain region. So if this were connected to the nucleus accumbens ,then the rat would be likely to press this lever a great deal. And here we can see the location of the hypothalamus, where you’ll find the nucleus accumbens in the human brain.
Now it’s important to note that when this area was first described it was referred to as the “pleasure area” of the brain. But that’s not quite right, because it’s not really the case that it’s just pleasurable for the rat to receive stimulation to this nucleus accumbens area, but rather, that the rat is motivated to continue to seek out this stimulation. And so this area is now referred to as the “reward area” of the brain because it’s about rewarding, and it’s about motivation to pursue the behavior again in the future.
Now, you may have heard of this reward area of the brain before and you may have heard of the neurotransmitter dopamine in a popular context. This is one of the few neurotransmitters that most people have probably heard of and the reason for that is that this area of the brain, associated with rewards and motivation, primarily uses the neurotransmitter dopamine. And so when you engage in something like eating or sex you trigger the release of dopamine in this area of the brain. It’s also the case that this area is stimulated by certain recreational drugs like cocaine. So when somebody uses cocaine they get a rush of activity in the nucleus accumbens and this is what makes the drug pleasurable, but also what makes people become addicted to the drug because they’re motivated to seek out that stimulation again and again in the future.
Ok, so this helps us to understand why Kluver and Bucy’s monkeys had issues with eating behavior and sexual behavior because of damage to the limbic system including the hypothalamus. So they were no longer able to correctly identify what things are they supposed to eat, what things are they supposed to try to mate with. And you might think “well, how does this relate to fear?” so this brings us to the next area of the limbic system. Because we can see here a monkey that’s not showing fear in response to this snake, which normally a monkey would show fear in the presence of the snake. So what’s going on here?
Well, this relates to another area of the limbic system called the amygdala. And so here we can see the location of the amygdala, you actually have two amygdalae in the brain, one on the left and one on the right. And you can see it’s very close proximity to the temporal lobe which would have been surgically removed by Kluver and Bucy. And so we can see that, that’s probably going to interfere with the ability of the amygdala to operate properly and that’s going to be the explanation for the fearlessness that these monkeys showed. Because the role of the amygdala seems to be that it appraises a stimulus. It helps it to determine what sort of emotional response should I have to this stimulus?
So if it’s a snake, then you think “okay I should be afraid of this snake I should have the response of fear”. But if your amygdala has been damaged like it was in Kluver and Bucy’s monkeys then you’re no longer able to have that appraisal process working correctly and so you’re not able to determine whether something is a threat or not. So a researcher, you know, handling one of the monkeys, the monkey doesn’t feel threatened by this. Or when seeing a snake, doesn’t have the emotional response that it would normally have. That’s because of damage to the amygdala.
Ok, in the next video we’ll take a look at some of the different pathways that are used in this process of appraising a stimulus. I hope you found this helpful, if so, please like the video and subscribe to the channel for more. Thanks for watching!
