U: Really? There are chocolate researchers?

J: Haha! Not really chocolate researchers, I meant neuroscience researchers!You see, eating chocolate is an experience in itself. So neuroscientists study the effects different experiences like eating chocolate have on our brain.

[02:02] U: Wait, eating chocolate is an experience?

J: Yes, eating chocolate is very much an experience! Wait, I’ll tell you. Close your eyes and just listen to me. (In a meditative voice) Imagine I hand over a big bar of chocolate to you. The wrapper is shiny…you look at the chocolate and you already have a smile on your face. You unwrap and smell the sweet chocolaty fragrance. The chocolate is starting to melt on your fingers. you take a bite and you feel the smooth texture of chocolate on your tongue as it slowly melts away...

U: Oh My Gosh! Yes! There is fragrance, texture, taste, and oh, all the good memories of eating chocolate!

[02:42] J: Exactly. Now you see, there are multiple aspects to eating chocolate. And that's why you need neuroscientists to find out how the brain deals with all these together! U: Have they figured that out?

[03:00] J: Yes! Yes, They have. So, let’s zoom into the brain a little. There is a region in the brain called the Orbitofrontal cortex, just behind your forehead and above your eye sockets. This Orbitofrontal cortex takes what is happening inside –the tummy saying it feels hungry – and connects it to what’s happening outside your body – eyes saying that it sees chocolate, and connects the two like “I’m hungry and I see chocolates, I want to eat it!”

U: Woah…That’s so cool!

[03:38] J: Exactly. It also decides if a task you did is worth rewarding or punishing. Like if you remember from our discussion about, ‘Why do we find babies cute?’, we get rewarded with that emotion of cuteness when we see a baby.

[03:57] U: So, the orbitofrontal cortex is rewarding the chocolate eating experience? But why?

[04:05] J: Yes, it is! Now, coming to your question, ‘Why do we find chocolate so tasty or why do we like chocolates so much?’ Let's start from the basics. Chocolate is a mixture of cocoa powder, cocoa butter, milk solids, and loads of sugar.

[04:23] U: Seems like chocolate has a lot of ingredients that make eating chocolate an experience.

[04:28] J: Exactly, so let's go one by one with the effect of each ingredient individually.
Starting with Cocoa. Cocoa is what gives chocolate its sort of “chocolaty” flavor. Trivia! Chocolate is actually derived from a traditional preparation of cocoa water. Originally cocoa beans were simply boiled in water and that’s what people used to drink. And that’s where we got chocolate from.

[04:56] U: Let me guess, it is this flavor that we enjoy and like about chocolate, right?

J: Well, yes and no. The cocoa that is used to make chocolate is usually bitter actually. The chocolate that we eat nowadays and enjoy so much has a large amount of milk powder and sugar to get rid of the bitterness.

[05:18] U: Ah! Yes, those dark chocolate bars… they are always bitter!

J: Exactly! Dark chocolate has more cocoa content, and that's why you find it bitter. This is where other ingredients come in. It's the addition of milk powder and sugar that makes chocolate so delicious!

[05:37] U: (with disgust in tone) But I don't like milk with sugar, Jigyasa! J: You may not find milk with sugar delicious, but your brain totally loves it. What I mean to say is that our human body is programmed to look out for any food that gives us loads of calories or energy.

[05:56] U: Is this why it's more difficult to say no to chocolate when I am hungry?

J: Yes! And in fact, neuroscientists tested out what we feel when we eat more calories vs less calorie food. Foods with high calories and fats tend to make us feel better than foods with fewer calories or fat, especially when we are hungry.

[06:19] U: Interesting..but Jigyasa, how can chocolate make us feel good if it’s made with bitter cocoa?

J: We talked about the addition of high calorie milk and sugars to cocoa to get rid of the bitter taste, right?

U: Right.

J: And we talked about how the orbitofrontal cortex connects information in our brain, right?

U: Right.

[06:42] J: So let's put it all together. The enjoyable experience of chocolate comes from the milk, cocoa butter, and sugar, and the sweet and smooth texture of chocolate in our mouth… Now, the orbitofrontal cortex registers this - the high calories and the energy and the smooth texture and the sweetness, all of it together - as a positive stimulus. The orbitofrontal cortex says it's a good thing for your body and gives a reward. So you end up feeling pleasant after eating chocolate!

[07:22] U: So, let me get this straight, high calorie food, rich in fat is great for the brain to energize. And chocolate gives us all of that instantly! So the orbitofrontal cortex tells me “yay…you did a good thing”

J: Exactly! You got it perfectly right!

[07:42] U: Eating chocolate is indeed an experience! Ah, we have talked about chocolates so much today. It makes me crave for more, you know.

J: Hahaha! And you know Utsuka, if you eat chocolate now, the neurons in your orbitofrontal cortex will start firing rapidly and reward you for fulfilling your craving. In turn, it will make you appreciate chocolate even more!

U: This feels like an infinite loop of reward and craving! Let's go get some chocolate! Although I am curious to know if neuroscientists really really study people's brains while they eat chocolate!

[08:25] J: And now… it’s time to ask a scientist!

[08:30] U: Continuing our discussion about why we like chocolates, we now have Dr Nandini Chatterjee Singh, who is a physicist turned brain scientist from the National Brain Research Center, India.

[08:42] J: Dr Chatterjee, we just learnt that when we eat chocolates, there are multiple things that go on in our brain. We are experiencing the taste of the chocolate and then there are memories that we have with chocolates so it makes us happy. So similarly I want to ask you, how do these multiple components of something contribute to making one experience?

[08:59] N: So that is a big question and I think we are still trying to figure out what all goes into formulating an experience. But I will try to dissect to the best of my ability about what might be the components of such an experience? if you go back and see what are the components that go on to make chocolates, there is caffeine which is probably stimulant in chocolate. That caffeine is maybe acting on the attention aspect of it. So we have a tension coming into play, we have a reward coming into play. Already a combination of these two is going to make any experience memorable and flavourful. Another point that I just want to add is for any experience to become memorable it is important to actually participate in it. If you do a lot of things unconsciously, for example, just eating a bar of chocolate without paying attention to it, the experience is not very flavourful.But if you sit in a corner or wherever you are and give your attention to the chocolate, that experience is much more flavorful. That is a very important part of building the experience around chocolate. Chocolate and apparently even dark chocolate particularly contains something, phenylethylamine, and this is something that is a precursor to dopamine which is the feel good hormone in the brain. And that is found in the chocolate. So we already have three things again now, there is dopamine, there is attention and there is reward in the brain now. And there is stimulation that is coming in from caffeine. So these are pretty much the set of ingredients that can really make any experience good and when they are all present in chocolate it is bound to make it very relevant and important and rewarding for us. A balance of all of these in the right proportion is what gives chocolate its flavor and adds to that experience. If you eat too much chocolate, you don’t enjoy it so much, I think. The timing and proportion make a huge difference, I think, it is primarily the combination of these four. And yaa I am sure there is some sugar in there, which adds to glucose which adds to the enjoyment.

[10:58] J: Yes, Yes. But as you said, these scientists have studied these chemical molecules in the brain. It makes us wonder, how do you study these things in the lab? Because definitely, we can not open up the brain and study these molecules, there must be some machines that help you understand these things…

[11:14] N: So in humans you can study it in multiple ways one is to just do a well designed, well controlled behavioral experiment where you get people to eat a bar of chocolate and what you sort of randomly assign them. So you don't know who is eating chocolate and who is not. My own work is primarily focused on functional neuroimaging So essentially what you are doing in functional imaging is that there are certain regions of the brain that are participating in a particular activity. So in order to identify which parts of the brain are participating in that activity what happens is the energy required by those areas is sort of higher. They need to do more work. So they absorb some more of the oxygen to be able to create a difference in the dipole moment and that is detected by the scanner. Because it is a Magnetic Resonance Imaging scanner. That’s the activity that happens and then this is then subjected to analysis. So you are using the principle of physics there which you can then amplify to try and understand the biology behind it.

[12:28] U: And is this measured like the ones we see on the TV where people show how the brain studies where they have these gigantic machines? J: MRI is what it’s called.

[12:38] N: yeah. And what is interesting is that… this is completely non-invasive and not at all harmful. When I started this work with children. When I tried to see how children learn to read. How children were so much more willing to get into the scanner because they were so excited. We told them that we are going to take photos of your brain. And after they did the task, the kids came back and told me, “anytime you want to study ‘how to play games?’ Please call me and I’ll play games in the scanner for you”. U: or maybe eat chocolate… N: absolutely.

[13:11] J: So you mentioned that there is a lot of physics that's behind MRI machines. Why does the intersection between physics and brain science interest you and how did you get into this?

[13:19] N: So I studied physics for a living for a long time and I did my phD. The physics I studied was primarily theoretical physics, not so much experimental physics. In those days I was looking at complex systems, looking at a lot of mathematical and computational modeling. And during my postDoc people were applying methods of physics into biology. So I thought I would try my hand and try to understand some of this. And then I got into a lab that was again applying mathematics to study the properties of neurons. So essentially what I was given was signals, which were signals recorded from the brain. So that’s what I started doing. During that time, I also started to see that there was a lab at UC, berkey which was looking at zebra finches. And zebra finches are birds which learn to sing but they follow a model of learning which is very similar to humans. So it is used as the model to study human learning.I got fascinated by this entire model for trying to use zebra finches and I got attracted to what the experimental part of the science is. But here is what is surprising, it surprised even me. I came back to a position in India again to study computational neuroscience after this post doc. But then NBRC got an MRI Scanner and I was a physicist who understood how the MRI works. So I was given a task: you have this machine here and you understand how it works. So you should start using it. And I was studying speech, not so much language. And so because i understood the physics of the scanner, i got into starting to study it. My students and I have pretty much learnt how to use MRI scanner, functional imaging together. We learnt methods together, we read papers together and we pretty much liked each other. It was fun being a student again and I feel I just want to be a student all my life.

[15:16] J: super interesting. Like the fact that you can learn at any stage in your life and be interested in something new and taking up the challenge in itself is quite inspiring.

[15:27] U: And I think one thing led to another for you. You started as a postdoc studying the physics part of the world you mentioned and then you had those transitions.

[15:35] N: You just need to be unafraid and willing to learn. My only advice is don’t stop learning. So I think curiosity is critical to being passionate in anything you do and in anything you enjoy and that’s why curiosity is important. The world is such a wonderful place that if you are not curious, you’ll miss out on understanding a lot of the world, you know. If you just follow what everybody is telling you, you are looking at it from their eyes and not from your own eyes. And that is something you are missing out on very much. So curiosity, reflection, introspection, I think are critical to science.

[16:14] U: Thank you so much, that's been so lovely Nandini.

[16:19] J: So Utsuka, What did we learn today? U: Eating chocolate is an experience. The components - that is, a mix of sugars, fats, milk, cocoa, and caffeine - together make our energy craving brains very very happy. J: And Dr Nandini Chatterjee explained to us how they study these happy experiences using the principles of physics. J: But listeners, what we know about the brain’s wiring might change as we get more evidence over time. U: Who knows, in the future it might be you who would study human brains and find out something about them that we never knew before!

[17:06] U: So that’s it for today.

J: If you want to know more about today’s scientist, we have linked his profile in the Show Notes!

U: If you have any questions that you want us to explore, shoot them away to Indiaakswhy@gmail.com

J: If you'd like to directly talk to us directly, then join the fun, join the fun on our Telegram Group. Link in the show notes.

U: For updates on IndiaAsksWhy, follow us on @IndiaAsksWhy on Twitter, and @India_AsksWhy on Instagram.

J: Shweata N. Hegde and Ruchi Manglunia are the hosts for the podcast.

U: Indulekha M.S. edited this episode.

J: And Khushi Goel transcribed it.

U: and we are funded by the indiabioscience’s second outreach grant.

J: Until next time! Till then, stay tuned and stay curious.