Tag Archives: taste perception

Where is the Spicy Food in Paris?

On every street in Paris, there are three things you are certain to find: a boulangerie (or two or three), some sort of bistro/brasserie/café, and a Franprix (my personal favorite, a small-scale grocery store). Clearly, cuisine is central to Parisian life. And often, the options boil down to baguettes, wine, and cheese.

a typical boulangerie (“Savouries Counter – La Renaissance Patisserie” by avlxyz is licensed under CC BY-SA 2.0)

As a lover of spicy foods, I was at a bit of a loss. After about a week into my stay in Paris, I was ready to reintroduce some of the essential components of my normal diet—mainly, I’m referring to chili paste and other spices. Perusing the Franprix directly below my apartment, I was shocked to see that there was only one option for hot sauce. Not only this, but every café and restaurant I had been to showed no promise of the tongue-scorching, eye-watering foods I love. So I had some questions: why do I enjoy spicy foods so much? How are they registered in my brain? Is there a certain part of my brain—specifically for processing spicy taste sensations–that is more active for me than for a French person?

my chili paste from Franprix (Personal Image)

Before attempting to tackle any of these questions, let’s first explore how our brains perceive sensory information from the world around us.
The five basic senses–sight, sound, smell, taste, and touch–all have particular areas of the brain (in the bumpy outer layer called the cortex) devoted to receiving signals from our eyes, ears, nose, mouth, and skin, respectively. The area of the brain that registers taste is called the gustatory cortex.

Basic taste perception  (Image from Frontiers for Young Minds)

Nestled in taste buds scattered about the surface of the tongue, special receptor cells interpret chemical stimuli as sweet, salty, bitter, sour, and umami. From there, signals are sent to sensory neurons and into the brain through cranial nerves (Breslin and Spector, 2008). Spicy foods are detected a bit differently than other tastes, since these signals involve pain receptors (Immke and Gavva, 2006). But, recent neuroscience research has been determined that these signals still activate the gustatory cortex, so they count as a legitimate tastes (Rudenga et al., 2010)! Therefore, it seems that French cuisine is indeed missing an entire taste sensation, and it happens to be the one that is my favorite.

Taste bud (Image from LumenLearning.com)

Now that we’ve legitimized these piquant flavor sensations, let’s dive deeper into the neuroscience behind them.

While scientists still don’t understand exactly how taste perception works, it is clear that capsaicin (the chemical responsible for the spicy qualities of many of my favorite foods) actually results in unique brain responses. Unlike the other tastes, spicy sensations are often accompanied by the release of endorphins (explaining how they can be perceived as pleasurable) and activation of the autonomic nervous system. This unconscious system of bodily regulation is responsible for the perspiration, higher body temperature, and a faster heart rate associated with “hot” foods (McCorry, 2007).

In a 2015 study entitled “The Brain Mechanisms Underlying the Perception of the Pungent Taste of Capsaicin and the Subsequent Autonomic Responses,” Kawakami et al. (2015) investigated how these bodily responses happen after someone eats spicy food. The authors knew that the gustatory cortex (consisting of the middle and posterior short gyri, or M/PSG, of the insular cortex) must somehow be in communication with the brain area controlling autonomic system responses (the anterior gyrus of the insular cortex, or ASG). But, it wasn’t clear how this communication was happening.

In order to test this, the researchers administered three different taste solutions (spicy, salty, and neutral) to twenty human study participants. As the subjects tasted the solutions, the researchers took a look at their brain activity.
The method they used to analyze brain activity is called functional magnetic resonance imaging (fMRI). This produces high-resolution images of the brain while it is in action. Blood oxygenation level-dependent (BOLD) signals show where oxygenated blood is being used, indicating which regions are using up the most resources (Logothetis, 2003).

The ASG and M/PSG (Image from Frontiers in Human Neuroscience journal, Kawakami et al., 2015)

After performing this test, the researchers compared the brain images from the subjects. Their main findings were that there was coordination between the activity of the M/PSG and the ASG when people eat spicy foods. This could mean that these two brain areas are syncing up in order to produce symptoms like sweating and a quickened heartbeat after spicy food is consumed. Moreover, these results support the findings of another study done with mice, which concluded that cells in the ASG and M/PSG synchronize their activity patterns when capsaicin is tasted (Saito et al., 2012).
Kawakami et al. (2015) also found that the ASG was even more active than the M/PSG in response to capsaicin. Not only that, but both brain regions were significantly more active in response to capsaicin compared to the other solutions!

In sum, this study and previous work has helped to explain how the brain registers the taste of “hot” foods in the gustatory cortex and coordinates it with autonomic nervous system activation. However, the researchers only tested three taste sensations, and clearly, there is still much to be discovered about how the neuroscience behind gustation. Future work will likely take a closer look at the connection between the ASG and the M/PSG, possibly providing more insight into why some people (like me) find these mildly painful sensations more enjoyable than others.

   Baguettes are a staple in the                   Parisian diet (“Bag It” by Very Quiet is licensed under CC BY-SA 2.0)

In the meantime, perhaps knowing that eating spicy foods more fully engages the brain will inspire the French to literally “spice up” their diets and rethink that bland baguette, or at least offer more options in their grocery stores. That would make this hot sauce-lover very happy, and it would add a whole new dimension to French cuisine!

 

References:

Breslin, P.A., Spector, A.C. (2008). Mammalian taste perception. Current Biology. 18:R148-155. doi: 10.1016/j.cub.2007.12.017.

Immke, D.C., Gavva, N.R. (2006). The TRPV1 receptor and nociception. Seminars in Cell and Developmental Biology. 17:852-591. doi: 10.1016/j.semcdb.2006.09.004.

Kawakami, S., Sato, H., Sasaki, A.T., Tanabe, H.C., Yoshida, Y., Saito, M., Toyoda, H., Sadato, N., Kang, Y. (2015). The brain mechanisms underlying the perception of pungent taste of capsaicin and the subsequent autonomic response. Frontiers in Human Neuroscience. 9:720. doi: 10.3389/fnhum.2015.00720.

Logothetis, N.K. (2003). The underpinnings of the BOLD functional magnetic resonance imaging signal. Journal of Neuroscience. 23:3963-3971. doi: 10.1523/JNEUROSCI.23-10-03963.2003.

McCorry, L.K. (2007). Physiology of the Autonomic Nervous System. American Journal of Pharmaceutical Education. 71:78.

Rudenga K., Green B., Nachtigal D., Small D.M. (2010). Evidence for an integrated oral sensory module in the human anterior ventral insula. Chemical Senses. 35:693–703. doi: 10.1093/chemse/bjq068.

Saito, M., Toyoda, H., Kawakami, S., Sato, H., Bae, Y.C., Kang, Y. (2012) Capsaicin induces theta-band synchronization between gustatory and autonomic insular cortices. Journal of Neuroscience. 32:13470-13487. doi: 10.1523/JNEUROSCI.5906-11.2012.

Images (in order of appearance):

https://www.google.com/url?sa=i&source=images&cd=&ved=2ahUKEwik5pOayNDiAhUFfBoKHRppA28QjRx6BAgBEAU&url=https%3A%2F%2Fwww.pagesjaunes.fr%2Fpros%2F05362487&psig=AOvVaw2ocJ8aEu44zmFV0LxJzoWx&ust=1559762799131578

https://kids.frontiersin.org/article/10.3389/frym.2017.00033

https://www.google.com/url?sa=i&source=images&cd=&ved=2ahUKEwjZqu6RzdDiAhVZBGMBHaXYCI4QjRx6BAgBEAU&url=https%3A%2F%2Fcourses.lumenlearning.com%2Fwaymaker-psychology%2Fchapter%2Freading-taste-and-smell%2F&psig=AOvVaw1-_gpFcoSBHOxphR9YgJhr&ust=1559764284849243

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4717328/

 

Hyperlinked Videos/Sites:

https://youtu.be/TuVcnR5zAWo

https://www.youtube.com/watch?v=wGXoYippog8

https://neuroscientificallychallenged.com/blog/2013/05/what-is-insula

Blame it on the Music

This past week I got to immerse myself in the most distinctly French experience I’ve had since arriving in Paris – le festival de musique – a festival that’s essentially a giant excuse for everyone in France to leave work early, throw back a few drinks and enjoy music on every street corner, bar, park, and metro station in the city.

It was an amazing day, night, and morning.

There was such a diversity of interesting music – a solo guitarist playing tunes from “dirty dancing” to a bunch of kids, two dueling DJs (the one with a portable smoke machine won), a couple of Rastafarian reggae singers on the RER train, and even a man playing a collection of giant bells on truck bed outside Notre Dame. Just as interesting was the diversity of behavior amongst those listening to the music, specifically their drinking behavior.

Being the upstanding, responsible, academic individual that I am, I used my scientific observation abilities to hone in on the type and amount of alcohol being consumed by the groups listening to each genre of music. I then used this data to make educated decisions about which music attracted the most degenerate groups so that I could join them avoid them. 

NBB students enjoying the portable smoke machine.

Most of the Parisians seamed to be keeping their drinking in check. Those listening to the blues street musicians were sipping on wine and beer, the large group around the truck-bell musician was doing the same, and not surprisingly, the kids surrounding the solo-guitarist weren’t tossing back too many brews. The dueling DJs were a different matter though, and I had to unfortunately dedicate more time there to document the significantly larger quantities of wine consumed by the audience – at one point I even saw a flask and a mini-keg!

I witnessed the most alcohol consumption later that night though, when I followed the deep boom of a bass to a large dubstep-rave outside the Odeon metro station. As I approached the mass of people jumping in synchrony to the deafening music it quickly became apparent that these festival-goers had traded their wine for many liters of flavored vodka.

This sparked my curiosity, why were some groups heavier drinkers than others? Was there something about dubstep and the DJ-house music that caused those listening to drink more? There was a significantly higher percentage of young people at the rave but that doesn’t necessarily account for why they were drinking hard alcohol while the college-aged kids elsewhere were drinking beer and wine. I needed to do some research.
The Effect of Noise on Taste 

The truck bell choir. Definitely the most interesting instrument of the night!

In 2011, an article published in the journal Food Quality and Preference, looked at the effect of music and noise on how 80 college-aged individuals perceived the taste of alcohol (Stafford et al., 2012).

The study was pretty simple. When each participant entered the lab they were blindfolded and given a set of four different solutions (bitter, sour, sweet, and salty) to taste so that they had a baseline to compare against for the rest of the experiment. The students then put on headphones and were divided into four groups. One group had house music played in both ears, another had a news article being read in both ears, a third had music playing in one ear and the article in the other, and a fourth heard neither noise. The members of each group were then given alcohol of varying concentrations (with mixers) and asked to rate the level of sweet/bitter/sour/salty taste and overall strength of the alcohol in each drink (on a scale of 1-100).

Before we evaluate the results it’s important to first think about how the researchers controlled for external factors that might affect the data (like different alcohol preferences in the subjects, mood at the time of the study, type of music they normally listen to, etc.). It appears that the researchers did account for most of these issues, and they chose students with standard alcohol habits, no known taste aversions, and who were in average moods. They also chose the music genre and alcohol mixers based off of an initial study of the preferences of ten students. However, it would have been great to see the house music compared to other genres like jazz and country to make sure that the data wasn’t genre-dependent.

The results showed that those listening to music in both ears actually found the alcoholic drinks significantly sweater than the other three groups. Additionally, the ability to discern between the different strengths of alcohol was significantly lower in the music/news and only-music individuals than the other two groups, a result that has been shown in other papers (Seo et al., 2012). The fact that music only appeared to effect sweetness perception and none of the other three tastes is especially interesting because on average, the sweater alcohol, the more it gets consumed (Lanier et al., 2005). 

How does this all occur in the brain?

Location of Odeon rave!

There are very few articles that show how music affects taste perception in the brain. One thing that is somewhat similar is a process known as sensory deprivation. In sensory deprivation, one sense in eliminated and because of that another sense gets stronger. A perfect example of this would be how blind individuals often have a very good sense of touch. It’s been shown that the louder a noise the more it inhibits a person’s ability to distinguish taste (Woods et al., 2011). The music at the rave was much louder than anything I had heard at the festival, so maybe the reverse of sensory deprivation was occurring. Perhaps the Parisians’ sensory systems were so over-stimulated by the loud music that they were less able to perceive the alcohol concentration, leading to the consumption of more and harder alcohol. Additionally, the music might have made the vodka taste sweeter, making it even easier to drink. This is primarily speculation though, and lack of concluding evidence makes it difficult to know exactly what was happening in the brain. Perhaps I will have to conduct a research study of my own to determine the regions of the brain involved, as well as the effect of different music genres on alcohol perception. I wonder if any Emory students would volunteer for such a tasking experiment!

 

– Camden MacDowell

 

Works Cited

Lanier, S. A., Hayes, J. E., & Duffy, V. B. (2005). Sweet and bitter tastes of alcoholic beverages mediate alcohol intake in of-age undergraduates. Physiology &Behavior, 83(5), 821–831.

Stafford L., Agobiani E., Fernandes M. (2012). Effects of noise and distraction on alcohol perception. Food Quality and Preference 24: 218-224

Seo H., Hahner A., Gudziol V., Scheibe M., Hummel T. (2012). Influence of background noise on the performance in the odor sensitivity task: effects of noise type and extraversion. Exp Brain Res 222:89-97

Woods, A. T., Poliakoff, E., Lloyd, D. M., Kuenzel, J., Hodson, R., Gonda, H., et al.(2011). Effect of background noise on food perception. Food Quality and Preference 22(1), 42-47