Category Archives: Neuroscience

How Can You Tell I’m American?

Posted on June 19, 2013 by | 7 comments

One of the greatest challenges about being in Paris is being constantly exposed to a foreign language. I have found that fewer Parisians than expected speak English. Having studied French for a number of years, I am always eager to test my ability to communicate with native French speakers. I try to practice French in Paris as often as possible, whether it is through ordering food (obviously my most important application of the language), asking for directions, or even giving directions sometimes. Just a couple of days ago I asked a young lady for directions while on the metro and even though I knew that I had appropriately phrased my sentence in French, she responded in English. I knew that my accent had given away the fact that my native language is English, but I had expected her to respond in French. I have found myself in similar situations on many occasions. One time I was speaking French to an angry Cite Universitaire, the campus on which we are living, security guard after I had been locked out of my room and he responded in English, “I don’t speak English.” I was puzzled and in French let him know that I can speak French and he responded, “no you can’t.” I chose not to take this second encounter personally and instead began to wonder what about my speaking bothered him so much. It must have been my accent. Accent perception is such an interesting concept. We can tell what country a person is from, or even perhaps the city in which they were born not by listening to the words that they say, but by listening to the way that they say them.

Cite Universitaire (labeled as A)- where we have been living for the past 3 weeks.

In a study done by Adank et al. (2011), native monolingual Dutch speakers were played Dutch phrases in a Dutch accent and were also played the same Dutch phrases in an unfamiliar accent. While listening, the subjects’ brains were monitored using an fMRI scanner, a machine which uses magnetic imagining to monitor brain activity. The study showed that when the sound stimuli changed from the familiar to the unfamiliar accent, more of the subjects’ superior temporal gyrus (STG), a brain area involved in basic auditory language processing, became activated. The STG has also been shown to be associated with phonetic-analytic listening to speech. Perhaps this gives insight into as to why more of the STG is activated when listening to an unfamiliar accent; the brain is recruiting more cells to help analyze the phonetics of the speech because the speech is foreign. It is important to understand this because when French individuals hear me speaking French with an English accent, their STG becomes increasingly activated and they recognize that not only am I speaking in an accent, but then, through using other areas of the brain, may be able to understand what language I am speaking.

An exhibit in the Louvre Museum spelling out "love differences" in many different languages.

Whenever I’m on the metro and everyone around me is speaking French, it is difficult for me to decipher what they are saying unless they are speaking directly to me. I was curious as to the ways in which my brain would have responded to the sounds on the metro had I learned French at a younger age, but second to English. I wondered how the bilingual brain responds to language perception in general. In a study done by Archila-Suerte et al. (2012), a group of bilingual Spanish-English speaking children (whose native language is Spanish) and monolingual English speaking children were played the English syllables, “saf,” “sof,” and “suf,” while watching a silent film. These syllables were chosen because they are pronounced similarly in Spanish and would provide more insight into activation of the bilingual brain (perhaps because they may activate regions involved in perception of both languages). The subjects were told to focus on the silent film while the syllables were being played to them and simultaneously the group was analyzing the subjects’ brains using an fMRI scanner. The study was performed for young and older bilingual and monolingual children. The group found that the young monolingual and bilingual children had the STG activated (let’s call this area 1) while listening to the syllables. This data implies that the bilingual children when just beginning to learn the second language perhaps relates it to the first language and processes it in the same brain area. However, the older monolingual children still only had area 1 activated during the task whereas bilingual children had area 1 as well as other areas in the brain activated. This suggests that as bilingual children begin to master a second language more, their brain recruits other areas, other than area 1, to help distinguish between the two languages. Perhaps my brain is similar to the brain of the younger bilingual children, since I have not yet begun to master the French language. My brain may not be able to recruit other areas to help area 1 decipher a language other than English and this may be why I am unable to easily pick out French words and conversations while on the train. However, French individuals who are able to easily recognize my accent, process what my native language is, and then respond in my native language perhaps have activation of other brain areas which help the STG decipher the language. This is due to the idea that they are bilingual and no longer need to relate their second mastered language to their native language. It would be interesting to see what the combined results of the first and second study would be; to pursue a study that looked at monolingual and bilingual individuals’ brain activation to speaking their common language in an accent. I am curious to see if by being well versed in more than one language, bilingual children are able to recognize accents easier. Maybe one day I’ll master the French language enough to not have to constantly compare it to English! I guess I’ll just have to ensure that this isn’t my last trip to Paris…

–          Ankita Gumaste

Adank P, Noordzij ML, Hagoort P (2011) The role of planum temporal in processing accent variation in spoken language comprehension. Human brain mapping 33: 360-372.

Archila-Suerte P, Zevin J, Ramos AI, Hernandez AE (2012) The neural bases of non-native speech perception in bilingual children. NeuroImage 67: 51-63.

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Musée du Parfum & Synesthesia

Posted on June 18, 2013 by | 1 comment

This afternoon we went to the museum of perfume near the Paris opera house off Metro 8.  The museum is opened by a perfumery called Fragonard Parfumeur.  Fragonard Parfumeur was established shortly after WWI by an entrepreneur named Eugene Fuchs in 1926.  During the tour, we learned about different concentrations of perfume, their making techniques as well as the correct way to put perfume on yourself.  For example, Eau de Toilette is around 10% aromatic compound while the actual perfume is 20%.  Towards the end of the tour, we were given strips of paper scented with different perfumes.  One particular perfume named “Juste un baiser” or “Just a kiss” smelled sweet.  The perfume almost smelled like strawberry and mandarin orange dipped in honey.

Map of the Museum of Perfume

It is interesting how people often use adjectives for taste, or even food items to describe a smell.  We don’t hear people say this flower smells red, or this perfume smells loud.  This must indicate that there are some sort of overlap of brain processing for taste and smell.  This phenomenon is called “synesthesia” in which the stimulation of a sensory pathway leads to involuntary activation of a separate sensory pathway.  There are many different types of synesthesia that are not common to the majority of us.  For example, people with color-graphemic synesthesia view letters and numbers with a specific color (Rich and Mattingley, 2002), and people with number-form synesthesia view numbers in a specific location in space (Sagiv et al., 2006).  Therefore, odor-induced taste might be a universal form of synesthesia that most of us have experienced.

Different types of perfume

If odor-induced tastes are so similar to taste itself that people describe an odor “sweet”, then these odors are probably processed in the same area of the brain as tastes.  Not surprisingly, there are already multiple papers suggesting that the insula, part of the primary gustatory cortex that is responsible for the initial processing of gustatory signals, is also activated by odors that are able to induce taste-like sensations (Stevenson and Miller, 2013).  Instead of looking at the primary taste cortex, Stevenson and Miller (2013) investigated the two secondary gustatory processing areas of the brain: the orbitofrontal cortex (OFC) and the amygdala to see whether odors that induces tastes-like sensation are also processed through similar areas of the brain.  To test their hypothesis, they put 9 patients with brain resections in the anteromedial temporal lobe (AMTL) that included the amygdala, 3 patients with OFC damage, and 42 healthy controls through a series of gustatory and olfactory tests.  All test subjects were presented with 2 sweet-smelling odors (chocolate and plum) and 2 non-sweet-smelling odors (Vegemite and oregano).  An “odor-taste quality score” was based on the test subjects’ ratings of whether a smell is sweet, sour, salty, or bitter compared to the expected taste of the odor (Stevenson and Miller, 2013).  The result of this study shows that AMTL patients, while impaired in gustatory senses, were unimpaired in odor-induced taste tests.  On the other hand, one of the three OFC patients who was severely impaired in gustatory senses, was also impaired in odor-induced taste tests.  The data indicates that one of the two secondary gustatory processing areas, the OFC, is involved in both the processing of tastes, and odor-induced tastes.  Stevenson and Miller (2013) further showed that OFC and insula both have the same type of cells that are more responsible for the discrimination of tastes while the amygdala has cells that supports the recognition of tastes.  This is probably why both the insula and the OFC are needed for the processing of odor-induced tastes while the amygdala is not.

Red part shows the amygdala.

Green part shows the Orbitofrontal cortex (OFC)

This study shows that odor-induced taste is a type of synesthesia that is experienced by the majority of us, which also explains why we often use gustatory adjectives to describe a smell.  However, I think further research is needed to prove this concept because of the low sample size and the fact that only 1 out of 3 OFC patients showed correlation between impairment of taste and odor-induced taste.  In addition, there might be other unknown brain-related problems in these patients, which will affect the interpretation of the data.  Furthermore, an fMRI study of the areas of the brain are active during odor-induced taste tests could potentially provide a more accurate indicator for the overlap of brain processing area of taste and odor-induced taste.  Aside from all the potential flaws of the study, at least now we know that there are biological evidences behind all the taste and food-related description of different kinds of perfume!

-Eric Yao

References:

Rich AN, Mattingley JB (2002) Anomalous perception in synaesthesia: a cognitive neuroscience perspective. Nature reviews Neuroscience 3:43-52.

Sagiv N, Simner J, Collins J, Butterworth B, Ward J (2006) What is the relationship between synaesthesia and visuo-spatial number forms? Cognition 101:114-128.

Stevenson RJ, Miller LA (2013) Taste and odour-induced taste perception following unilateral lesions to the anteromedial temporal lobe and the orbitofrontal cortex. Cognitive neuropsychology 30:41-57.

 

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Musée du Chocolat

Posted on June 18, 2013 by | 4 comments

Before I even set foot in Paris, I had an agenda to tend to—buy every friend and family member enough chocolate to hold them over until their own trip to France. As (arguably) the biggest dark chocolate fan on the east coast, I have gone out of my way to make sure I try chocolate (in all forms) from all over Paris. I have run the gamut by trying chocolate bars from our favorite local grocery store (shout out to Mono Prix) to inhaling the chocolate pastries sold at Ladurée. Tending to my chocolate cravings in Paris turned out to be much easier than expected…

Chocolate Pastries at Ladurée (yum)

Needless to say, I was beyond excited when I saw that a trip to a chocolate museum was conveniently worked into our syllabus a day-off activity. Probably a bit too excited, the other students and I worked our way through the Parisian Metro and RER systems and arrived at “Choco-Story – Le musée gourmand du chocolat” earlier this week. Walking into the hands-on museum, we were hit with a wave of the sweet scent of chocolate, instantly putting everyone in a better mood. Part of our museum experience involved a chocolate workshop where we actually learned how to make bite-sized chocolates, and we luckily got to package the chocolates to bring back to our dorm.

Chocolate Museum: 28 Boulevard de Bonne Nouvelle, 75010 Paris

After our workshop where we somehow managed to make chocolate without destroying the museum kitchen, we waited for the pieces to cool in the fridge. As soon as our chocolate was cooled and ready to eat, I instantly ate maybe one too many pieces. Regardless, I was completely satisfied with my experience at the museum and our homemade treats. At this point, I’m sure you’re wondering why a chocolate field trip was worked into our neuroscience syllabus. Chocolate, aside from being central to Parisian culture, is responsible for producing pleasurable, hedonic effects and can therefore activate various brain areas (Rolls 2005). It has, for this reason not only been used as an incentive in various animal experiments, but its’ effects on changing activity in different brain areas have also been studied.

The neuroscience student in me wondered why some students were not as excited as I was about our chocolate museum expedition. Doesn’t everyone love chocolate? Why are there some people who don’t have chocolate cravings? Current neuroscience research is exploring the physiological implications behind cravings, emphasizing the brain systems that control our food intake. It turns out that people, like me, who crave chocolate actually show heightened physiological reactivity to images of chocolate. This means that there are measured changes in blood flow in different areas of the brain (such as the orbitofrontal cortex, the insula, ventral striatum and midbrain) in response to chocolate pictures (Small et al., 2001). What does this mean for choco-holics?

Spilling chocolate all over the kitchen floor....

A recent study tested the actual brain activity differences across individuals who craved chocolate and those who didn’t have these characteristic cravings (Asmaro et al., 2012). Researchers recruited undergraduates and asked them to fill out a chocolate-craving questionnaire, which was used to objectively measure “chocolate cravings”. After taking all of the data from these questionnaires, the researchers categorized the participants into one of two groups: chocolate cravers and non-cravers. The behavioral task of this study involved showing three types of images to both groups of participants. Both non-cravers and cravers were shown images falling under the following categories: chocolate, neutral and target. The chocolate stimuli category had pictures of dark or milk chocolate (yum), the neutral category had pictures of bland, uncooked foods (like pasta, for example) and the target stimuli category included random pictures of chairs (Asmaro et al., 2012).

There were two main sessions for this study: before eating chocolate and after eating a delicious piece of chocolate. In each of the two sessions, 220 images (100 chocolate, 100 neutral and 20 chairs) were presented in blocks. The participants (in both groups) were told to keep their eyes fixed on the screen as these images came up, and as soon as a target picture (a chair) appeared, participants had to press a key on a keyboard. After this task, the participants were asked to rate their craving for chocolate on a scale of 1 to 5. While this task was going on, researchers had an electroencephalogram along the patient’s scalp. An electroencephalogram is simply a tool that neuroscientists use to measure and record the electrical activity in the human brain. The reason they used an electroencephalogram in this case was to have a way to measure the brain response to these different, presented images. This actual brain response is commonly referred to as an “event-related potential” (Asmaro et al., 2012).

The researchers found that when the chocolate craving group was presented with a picture of chocolate, their brain activity indicated that they had a greater desire for chocolate overall. The non-craving group, however, had a lesser desire for chocolate after the task (Asmaro et al., 2012). This shows that presenting the chocolate stimuli actually caused different neurological responses across the two groups—cravers and non-cravers. If we take a step back and apply this back to my chocolate obsession, it is probable that I may have had different areas of my brain activated when I walked into the chocolate museum and saw all of the chocolate merchandise and pictures (when compared to some of my not so excited classmates).

Cooling chocolate (the French way...)

Asmaro et al. (2012) also showed that in non-cravers, the early changes in an area of the brain disappeared after eating some chocolate. This suggests that certain brain mechanisms control the otherwise natural urge to continue to eat chocolate in non-cravers (Asmaro et al., 2012). In cravers, however, a similar area of the brain (the orbitofrontal cortex) showed no changes in activity even after eating chocolate. What does this mean for us chocolate lovers, then? Turns out certain areas in our brain, such as the orbitofrontal cortex, are more likely to tell us to stop eating chocolate if we are classified as a “non-craver”. For us cravers, however, chocolate is a “wanted stimulus with a high motivational value” (a value that we subjectively place on it) and so our brains don’t really tell us to stop as readily as the brains of our fellow non-cravers. This is due to the fact that we have grown to appreciate and place immense value on chocolate.

Turns out, studies on the effects of chocolate on the brain are quite popular—mainly because they provide us with insight on consummatory and dietary patterns in humans.  The question is now: are you a craver or non-craver, and what are you going to do about it? If you’re anything like me, I’ll see you at the local bakery scoping out the best chocolate pastries.

 

-Noareen Ahmed

 

References:

Asmaro D, Fern J, Valery S, Isabel T, Patrick C, Mario L (2012) Spatiotemporal dynamics of the hedonic processing of chocolate imags in individuals with and without trait chocolate craving. Appetite 58: 790-799.

Rolls E, McCabe C (2007). Enhanced affective brain activations of chocolate in         cravers vs. non-cravers. European Journal of Neuroscience 26: 1067–1076

Small D, , Zatorre R, Dagher A, Evans A, Jones-Gotman M (2001). Changes in brain activity related to eating chocolate. From pleasure to aversion. Brain, 124: 1720–1733.

 

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Sorbet, what have you done to me?

Posted on June 12, 2013 by | 5 comments

Who would have ever thought that the garden of Versailles harbored the frozen ambrosia of the Gods? Perhaps it was also the very spot where the Garden of Eden was cultured. Whoever brought this gift from heaven, in the form of a sorbet, must have had compassion comparable to Mother Teresa. In simpler words, the sorbet I bought for 2.50 Euros was absolutely delicious. With its pleasing bright red color and slightly tart but not too tart aroma made my day. I had to buy another one as soon as I finished because of how empty my life felt. How did this simple sorbet bring such strong sensation to my taste buds?

Well we know there are molecules in food that code for sweet taste. Imagine the molecule as a baseball and the protein receptor as a catcher’s glove. When these molecules hit specific protein receptors, they attach to a specific type of cell (type 2) on your taste buds and cause a series of reactions called a signaling cascade. The end result of this cascade is the creation of a signal, called action potential, which causes a release of specific molecules called neurotransmitters.In this case, ATP was the neurotransmitter that was released. ATP then attaches to protein receptors on another cell that is a part of the pathway to the brain where the information of sweet taste is passed along. That pathway is referred to as the afferent gustatory neural pathway. Finally, the information is sent to the gustatory cortex, a part of the brain that finally tells you that the pastries shown below are sweet.

So that’s how the brain processes the sweetness of these macaroons. But that doesn’t explain why it was so good. Sweetness is only one aspect of the desert. There is also the bright colors, the sweet smell, and other combinations of tastes that make up the macaroons that I ordered. It is proposed that certain aspects of the sorbet become integrated at different parts of the brain. In the anterior insula, things like taste, smell, and texture of the food are integrated (Small, 2012). This information is then sent to the lateral hypothalamus, where you process how much you like the food (Li et al., 2013). This information is also sent to the thalamus to be enriched with detail such as the temperature. It is truly amazing how the brain is able to receive all of this information, process it in different areas of the brain, and combine it to form our perception of the world.

Now here’s something interesting to think about. Do you think your sweet tooth is indicative of social behavior? A novel study was done showing social behavior of rats that have been bred for low sweet intake versus rats that have been bred for high sweet intake. Results show that rats bred for high sweet intake show a more dominant personality via “king of the milk” competitions (Eaton et al., 2012). Could loving your sweets mean that you’re a more dominant person or could it cause some sort of behavioral change (epigenetics?) that causes you to act more dominant?

When I was eating these , I felt alive. Perhaps those were just pleasure receptors in my brain activating. But perhaps throughout the years, the amount of sweets that I have consumed has caused not only a physical change in me, but also a behavioral one.

~James Eun

References:

Eaton JM, Dess NK, Chapman CD (2012) Sweet success, bitter defeat: a taste phenotype predicts social status in selectively bred rats. PloS one 7:e46606.

Li JX, Yoshida T, Monk KJ, Katz DB (2013) Lateral hypothalamus contains two types of palatability-related taste responses with distinct dynamics. The Journal of neuroscience : the official journal of the Society for Neuroscience 33:9462-9473.

Small DM (2012) Flavor is in the brain. Physiology & behavior 107:540-552.

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Confession of a Paris Rookie: I love métro music.

Posted on June 12, 2013 by | 9 comments

Dear Paris, 

We’ve only known each other for two weeks, and this is definitely going to sound cheesy. Here’s my confession. I am afraid I am already madly in love with you. Everything about you is perfect: the baguettes, wines, € 0.40 espresso, the countless museums and the dirty crowded métro. 

the metro

the train carrying too many people in the métro

Yes, I even love the dirty crowded métro that sometimes feels like a slaughterhouse, especially on Monday mornings. Regardless, the métro is the backbone to your existence, one part connecting to another. Occasionally, I find the true gem of the métro– the musicians. The metro musicians must audition to earn their stage. The RATP, the company that runs the métro, holds biannual auditions looking for talented musicians every year. Just today, I had the pleasure of listening to the happy and carefree accordion player when I, along with the rest of the NBB crew, nonchalantly landed on the wrong train.

jolly accordion man                                                                          (click to watch!)

So far I have seen the guitarists, violinists, an opera singer, and an accordion player, but regardless of the genre, I lose myself in the sudden rush of happiness when listening to these metro certified musicians.

In addition to the pure bliss, I quickly recall my street musicians days playing with my string quartet, thus making the experience more meaningful and emotional. One recent neuroscience study stated that there is a release of dopamine (the happy brain chemical that is also released during sex and food) in the striatum (the reward network in the brain) during the emotional experience of music (Salimpoor 2011). So this pleasure I get from music is not only attributed to the melodious tunes of the musicians but also the emotions they elicit. Additionally, the level of pleasure, measured by quantifying the dopamine release, is positively correlated to the emotional arousal (Salimpoor 2009). This may also explain why other métro travelers remain immune to this fleeting euphoria that I experience.

Then I started wondering how my musical history affected my brain. I have been playing the viola for ten years, performing at various centers, halls, weddings, parties and of course, the streets. What kind of brain changes could I have self-induced? Luckily, I was able to find a study that explored this exact question. A group of researchers in a collaborative study among McGill University, Mouse Imaging Centre, Boston College, and Harvard medical school recently published the study on how musical training shapes structural brain development of children. Because many studies have previously looked at the effect of music in the adult brain, this study distinguishes itself in not only in its exploration in the developing brain but also in relating these biological changes to behaviors (Hyde 2009).

In this study, 31 children around the age of 6 with no previous musical background participated. In the instrumental group, 15 children went through weekly half hour private keyboard lessons for 15 months, while the control group participated in a weekly general group music class in public school (Hyde 2009). To measure and assess the structural changes in the brain, the 31 children underwent an MRI scan, which is a tool that allows one to visualize the brain. There were two behavioral tests. One was a simple motor sequencing task, which is where the children press a particular number sequence that corresponds to finger 2-5. (2= index finger and 5=pinkie finger.) The second behavioral test was a melodic and rhythmic discrimination test where the children heard pairs of tunes to indicate if they were the same or different. In order to see how the instrumental training affected the children’s brain and behavior, they were tested before and after the 15 month period.

The results? Compared to the control group, the instrumental group showed bigger primary motor area, corpus callosum (the tissue that connects the left and right hemisphere of the brain), and primary auditory area. These structural differences also paralleled the behavior changes. The children in the instrumental group consistently performed better in the motor and the tune discrimination task. Basically, the children in the instrumental group demonstrated greater brain changes that greatly enhanced the way they used their fingers for motor functions and their ears to detect differences.

Although this study only looked at young children, music does not discriminate ages and benefits all! I am now starting to wonder how pervasive and practical music therapy is in the field of neuroscience…. but for now, I need some personal music therapy aka YouTubing French artists. Au revoir!

-Sehe Han the Paris rookie

References

Hyde, KL, Lerch J, Norton A, Forgeard M, Winner E, Evans AC, Schlaug, G. (2009). Musical training shapes structural brain development. The Journal of Neuroscience, 29: 3019-3025.

Salimpoor VN, Benovoy M, Larcher K, Dagher A, Zatorre RJ (2011). Anatomically distinct dopamine release during anticipation and experience of peak emotion to music. Nature neuroscience, 14: 257-262.

Salimpoor VN, Benovoy M, Longo G, Cooperstock JR, Zatorre RJ (2009). The rewarding aspects of music listening are related to degree of emotional arousal. PloS one, 4(10), e7487.

 

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Les Pâtisseries à Paris

Posted on June 12, 2013 by | 8 comments

“The treasures of France; I love Patisseries!” one of my friends of French origin exclaimed when he discovered that I had been taking full advantage of the fact that nearly every street corner of Paris is occupied by a Boulangerie, or bakery. “Window shopping” in Paris is not limited to its boutiques; in fact, what really catches my eye when walking down the street are the rows of colorful macaroons, tartes and a number of other mouth-watering pastries. However, the real reason why I’m in France is not for the pastries, although they are a delightful perk to the trip, but is to study neuroscience through Emory University. With class from 9:30am to 1:30pm, the other students on my program and I take full advantage of our hour lunch break. We have made ourselves regulars at a nearby bakery and devour their enormous baguette-sandwiches nearly every day; but perhaps even more intriguing than their sandwiches are their desserts. A friend of mine and I, each having an extremely dedicated sweet tooth, have set out to try every pastry, cookie, cake, and dessert sold by our favorite bakery. Although this may seem like a daunting task, we are now four days into our endeavor and have already sampled about a quarter of the treats offered at our bakery.

Now, being an avidly interested neuroscience student, it wouldn’t be right to discuss such amazing sensory perceptions without giving credit to the nervous system. Endocannabinoids are chemical compounds produced by the human body that act in certain areas of the brain to stimulate appetite and food intake.  Yoshida et al. (2010) studied two different groups of mice, one normal group which had the receptor for endocannabinoids, and one which had been genetically altered to lack the receptor for endocannabinoids. The lack of receptor in the second group prevents the group from being able to experience the effects of endocannabinoids. The group of researchers administered cannabinoids, synthetically made endocannabinoids, to both groups of mice and found that in those mice with endocannabinoid receptors, behavioral responses to sweet compounds increased and the response of taste receptor cells on the back of their tongues to tasting sweet compounds increased as well. In the mice without endocannabinoid receptors, no increase in behavioral or cellular activity was observed in response to cannabinoid injection. In addition, in normal mice, with endocannabinoid receptors, if the endocannabinoid receptors are blocked using a drug, the mice show a decreased response to sweet compounds. This last portion of the experiment hints to the idea that endocannabinoids may be involved in allowing the animals to perceive a sweet taste.  These findings, in general, suggest that perhaps endocannabinoids play a role in the perception and enhancement of sweet tastes. Yoshida et al.’s normal mice which were administered a cannabinoid would have really loved the desserts that I have been delving into for the past few weeks. It may be possible that as I make my way through the treats at my regular bakery, my body releases endocannabinoids, which act on certain areas of my brain that eventually communicate with my taste buds and allow me to taste the sweet, delicious desserts. Perhaps a combination of my body’s release of endocannabinoids and my love for sweets is what is propelling me so quickly through my task. At this rate I’ll be onto my next bakery in a week; watch out Paris, I’m a little girl with a huge sweet tooth.

– Ankita Gumaste

Works Cited

Yoshida R, Ohkuri T, Jyotaki M, Yasuo T, Horio N, Yasumatsu K, Sanematsu K, Shigemura N, Yamamoto T, Margolskee RF, Ninomiya Y (2010) Endocannabinoids selectively enhance sweet taste. PNAS 107:935-939.

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Fading Away…

Posted on June 12, 2013 by | 7 comments

When in Paris it is expected that you will see the Mona Lisa at the Louvre and the famous paintings and sculptures at Musée d’Orsay; but what I did not expect was to attend an exhibition full of manipulated light, motion, and optical illusions.  The Dynamo exhibition at the Grand Palais completely exceeded my expectations and quite literally messed with my perception of reality.

Location of Dynamo Exhibition

 What I would see in person did not match what my camera lens saw and often I would see images that seemed to move or change when I looked from a different angle.  One of my favorites is shown in the image below:

Optical Illusion from the Dynamo Exhibit

Unfortunately I didn’t take the best picture so it doesn’t quite work now, but at Dynamo when I stared at the center dot and rings, the outer light blue ring disappeared!  Of course my initial reaction was to jerk my head (thinking I was seeing things, or not I guess in my case) and the ring reappeared. This ended up being the intention of the piece and being the nerd that I am, I wondered how they did it. 

I did some research and found out that the phenomenon is called Troxler Fading, which is when you are fixating on a central object and the object in your peripheral vision fades away from your awareness.  Essentially your brain gets used to seeing the unvarying objects and fades them out so you can focus on the central object.  It’s similar to when you drop something in your lap, you feel it for a few seconds, and then forget it’s there until you feel it again when you move.  It is the body’s way of reducing sensitivity to constant stimuli, freeing attention to process the new things.  The diminished response to a repeated stimulus is called habituation (Lou, 1999).

One very interesting paper I found linked visual habituation (the fading) to adults with ADHD.  But first to understand the paper I had to understand how and where the Troxler Fading occurs.  Troxler Fading involves two major parts of the brain, the frontal lobe and the parietal lobe. When the parietal lobe was damaged, objects in the peripheral would fade faster than those with a functional parietal lobe.  In contrast, those with damaged frontal lobes rarely experienced any fading.  The conclusion was that the parietal lobe is necessary to maintain an image, but the frontal is important for the habituation of an object (Mennemeier et al., 1994).

Jacqueline Massa and Illyse O’Desky knew that people affected with ADHD have abnormal frontal lobe activity and wanted to see if their visual habituation was affected.  Since the damage to the frontal lobe was linked to no visual habituation, people with ADHD could have a diminished ability to fade out the unimportant things and therefore have a harder time focusing on one task.  They used several tests with Troxler fading, asking 21 adults with ADHD to indicate when the dot in their peripheral faded away.  The results of the study showed that adults with ADHD had to stare longer to get the dot to fade (habituation) than those without the disorder.  They concluded that the impaired habituation may explain why adults with ADHD have such a hard time focusing on one thing at a time; it takes longer for their brain to fade out unimportant stimuli (Massa and O’Desky, 2012).

Nerdy tangents like this are completely normal for me.  I see (or don’t see) something and have an urging desire understand it.  Most of the time I end up finding cool ways to link it to other things.  And now when I take my sister to the exhibition in July, I can explain to her how it all works, even though I’ll probably be the stimulus she fades away…

~Sarah Harrington

References:

Lou L (1999) Selective peripheral fading: evidence for inhibitory sensory effect of attention. Perception 28:519-526.

Massa J, O’Desky IH (2012) Impaired visual habituation in adults with ADHD. Journal of attention disorders 16:553-561.

Mennemeier MS, Chatterjee A, Watson RT, Wertman E, Carter LP, Heilman KM (1994) Contributions of the parietal and frontal lobes to sustained attention and habituation. Neuropsychologia 32:703-716.

 

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Baroque Music at Sainte Chapelle

Posted on June 12, 2013 by | 5 comments

 

Last week, we took a group trip to Sainte Chapelle, a Gothic church in the heart of Paris. Though many visit the church to admire the magnificent collection of 13th century stained glass and extensive collection of Christian relics, we were there to hear an authentic Baroque music concert. Much of the hour-long concert featured a trio of harpsichord, violin, and recorder, but at one point, the recorder player took a solo and switched from playing the soprano version of the instrument to the higher-pitched sopranino. After the recorder player began his solo on the stage, he proceeded to wander throughout the entire chapel—through the audience, along the walls of the chapel, and at one point even directly behind the seating area.

When I said "heart of Paris," I meant it.

As the soloist walked around far behind me, I noticed that I was able to identify where the sound was coming from even though I was facing the opposite direction. I immediately remembered a lecture from neurobiology class that covered the neural mechanisms involved in sound localization. The process depends on the fact that our brain has the ability to compare inputs from both ears. When sound emanates from a source, it usually is not exactly the same distance away from each ear, so when the sound reaches both ears, the difference is calculated and converted into an angle to the direction of the sound (Grothe, 2003). Oftentimes, the difference between arrival at each ear can be as little as 10 microseconds (that’s 1/100,000th of a second)!. This calculation of interaural time difference (ITD) occurs in the medial superior olive, a collection of cells in the brainstem.

Basis of interaural time difference

I was curious, though, if the same process was taking place during the concert. I remembered that the ITD calculations are particularly effective for low frequency sounds, certainly lower than the high-pitched sopranino recorder (Devore and Delguette, 2010). Additionally, I imagined that the tall ceiling and compartmentalized roof, typical of Gothic architecture, would create echoes that further complicate the use of ITD to localize sound. I looked into the matter, and found an article that attempted to explore how the brain’s ability to localize sound is affected by reverberation (Devore and Delguette, 2010). The researchers thought that the lateral superior olive, which uses interaural level difference (ILD) to localize sound rather than ITD, would be preferentially involved in sounds distorted by reverberation. In order to test this hypothesis, the experimenters used a technique called in-vivo electrophysiology, which places a collection of small recording electrodes into the brain and is able to isolate activity from single brain cells in awake, behaving subjects. Once the electrodes were in place, the subjects (in this case, rabbits) were exposed to a variety of auditory stimuli. The stimuli varied in direction, pitch, and reverberant nature so that the researchers could determine which pathways were in use in different situations. They found that the brain relies more heavily on ILD than ITD in reverberant situations, particularly for high-frequency pitches.

Beautiful? Yes. Reverberant? Absolutely.

While researching sound localization, I stumbled across another article that I found to be particularly interesting. I have always been amazed by conductors’ abilities to identify a single individual who misses a note in a 70-person ensemble. Researchers found that the constant exposure to wide field multi source sound environments experienced by conductors actually changes the way that conductors’ brains process the information (Münte et al., 2001). Not surprisingly, conductors outperformed both non-musical controls and pianists in accuracy of sound localization, but interestingly, recordings of brain activity during the task revealed that all groups utilized identical regions of the brain. This finding led the researchers to suggest that the intensive training and exposure that conductors receive simply trains their brain to more effectively use the sound localization pathways that we all use everyday. Take home message: the phrase “mental exercise” has a good deal of validity to it.

 – Max Farina

 

Works Cited:

Devore S, Delguette B (2010) Effects of reverberation on the directional sensitivity of auditory neurons across the tonotopic axis: influences of interaural time and level differences. Journal of Neuroscience 30: 7826-7837.

Grothe B (2003) New roles for synaptic inhibition in sound localization. Nature Reviews Neuroscience 4: 540-550.

Münte TF, Kohlmetz C, Nager W, Altenmüller E (2001) Neuroperception: Superior auditory spatial tuning in conductors. Nature 409.

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Château de Villandry and Lemon Balm

Posted on June 11, 2013 by | 7 comments

This past Saturday, we took a three-hour bus ride from Paris to the Loire Valley to visit two famous chateaus:  the Château de Villandry and the Château de Chenonceau.  Château de Villandry especially caught my attention because despite its rather plain exterior compared to other chateaus. It has one of the most beautifully designed gardens.  Château de Villandry have a long history since the 14th century, but most recently, Joachim Carvallo, a Spanish doctor and researcher, bought the property in 1906. As we stood on the upper levels of the chateau, I was amazed by the geometric designs of the decorative gardens that represented tender, passionate, fickle, and tragic love.  Carvallo renovated the château and designed medicinal gardens to further his research.  In addition to the medicinal herb garden, there are also flower gardens, vegetable gardens, and waters gardens, which are representative of renaissance style chateaus.

Chateau de Villandry

Decorative gardens in Chateau de Villandry

The medicinal herb garden is farther away from the main building because it was built in the 1970s by Carvallo’s grandson according to his original design.  The garden contains various different types of herbs, roots, and leaves that have therapeutic properties.  As I was meandering through the garden slowly, a slight scent of minty lemon caught my attention.  The scent originated from a little bush with green leaves that resembled the shape of mint leaves.  A little web browsing showed that the plant is called lemon balm, or Melissa officinalis.  Lemon balm is usually used to make herbal tea, which I don’t particularly like.  However, since Carvallo chose to have lemon balm planted in his herb garden, I am curious to find out the beneficial effects of this nice smelling plant.

Lemon balm has various therapeutic properties ranging from lowering anxiety to treating Alzheimer’s disease (Maguire et al.).  Lemon balm has such a wide variety of therapeutic uses because of its effects in many neurotransmitters that are important for neuron communication in the body.  Neurotransmitters are molecules secreted by one neuron to another for signaling purposes; most of them can be divided into two categories.  One group of neurotransmitters will increase the activity and electrical firing of the recipient neuron.  The other group of neurotransmitters will decrease the activity and electrical firing in the neuron receiving the molecules.

Lemon Balm (By quinn.anya)

Among many studies investigating possible usages of lemon balm for treating different diseases, a study on lemon balm extract’s ability to induce neurogenesis in dentate gyrus of hippocampus, an area of the brain that is responsible for forming new memories, seems particularly promising for treating many memory related diseases such as Alzheimer’s (Yoo et al., 2011).  Neurogenesis in the dentate gyrus focuses on the formation of granule cells, a cell type that is thought to be responsible for spatial memories (Colicos and Dash, 1996).  The process of neurogenesis starts with the proliferation of granule cell progenitors in the subgranular zone, which then migrate to the granule cell layer where the new granule neuronal cells are made (Yoo et al., 2011).

To see if lemon balm actually promotes neurogenesis, Yoo et al. set up three groups of mice.  The first group was fed with 50mg/kg lemon balm extract, the second group received a higher dose of 200mg/kg, and the last group is a control group in which the mice were fed with distilled water (Yoo et al., 2011).  All three groups were fed once a day for 21 days.  To track the effect of lemon balm on neurogenesis in the dentate gyrus, we have to monitor several proteins that are produced as by-products of neurogenesis.  Ki-67 is a protein that will be present in the cellular nucleus during cell proliferation.  DCX, another protein, is expressed in immature neurons, which is indicative of new neuron formation.  To see if these proteins are made in the dentate gyrus, antibodies that will attach themselves specifically to these two proteins were used.  To quantify how many antibodies are attached to these two proteins, a stain was performed on sections of the dentate gyrus after the antibodies were administered (Yoo et al., 2011).

The results of this study is astonishing in which there is a 7-fold increase in the level of Ki-67 in the mice group that received 200mg/kg lemon balm compared to the control group that received water.  Similarly, there is also significant increase in the level of neurons expressing DCX in the dentate gyrus for the two experimental groups that received lemon balm extract (Yoo et al., 2011).  The combined increases in expression of these two proteins indicate that neurogenesis of granule cells are increased due to the intake of lemon balm extract by the mice.

Although there are still many differences between mice and human, I think it wouldn’t hurt to drink some lemon balm tea once in a while.  If granule cell neurogenesis can be induced by lemon balm extract as suggested by the mouse model, drinking some lemon balm tea might actually improve my spatial memory and help me navigate through the complex RER and metro system in Paris! 

-Eric Yao

 

References:

Colicos MA, Dash PK (1996) Apoptotic morphology of dentate gyrus granule cells following experimental cortical impact injury in rats: possible role in spatial memory deficits. Brain Research 739:120-131.

Maguire MA, Dvorkin L, Whelan J Boston Healing Landscape Project – Melissa Officinalis. In. Boston University School of Medicine.

Yoo DY, Choi JH, Kim W, Yoo KY, Lee CH, Yoon YS, Won MH, Hwang IK (2011) Effects of Melissa officinalis L. (lemon balm) extract on neurogenesis associated with serum corticosterone and GABA in the mouse dentate gyrus. Neurochemical research 36:250-257.

 

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Monet and Memory

Posted on June 11, 2013 by | 11 comments

Claude Monet's "The Rue of Montorgueil in Paris. Celebration of June 30, 1878"

If you quickly glance at Claude Monet’s “The Rue Montorgueil in Paris. Celebration of June 30, 1878” as you visit the Musée d’Orsay, you can instantly recognize individual objects in this scene depicting a french celebration with crowds of people walking in the street. Look closer. The blocks of color on the flags are so blurred you may have trouble distinguishing one flag from the next. The crowds of people in the street are almost inseparable into individual persons. The typical Parisian gates on the bottom of the windows are nothing but dark blotches. Still, you can recognize these objects and people for what they are, even in a painting you have probably never seen before.

Musée d'Orsay in Paris, France

This ability has to do with a kind of memory your brain uses to identify something that you see, and it is called “object-recognition” memory (ORM) (Winters et al., 2008). Generally, the hippocampus is a brain part known to be very important in this kind of memory (Winters et al., 2008). This structure mainly houses declarative memories, such as the abilities to remember the name of the dessert that you picked up at a boulangerie or to tell taxi drivers the address you’re staying at while in Paris (Winters et al., 2008). Despite the importance of the hippocampus, it is not the only structure in the brain that houses memory. Brain structures like the orbitofrontal cortex, amygdala, and cerebellum also house components of memory. Even recently, parts of the cortex that decode visual information have been found to be important in certain types of memory, like ORM (Winters et al., 2008).

The brain processes visual information in a hierarchical manner. The photoreceptors in the eye sense spots of light and send signals to other neurons in the brain that activate to increasingly specific images. An important part of this system is the area known as V2, which splits into two parts. The lower area, known as the ventral part, allows for the abilities to tell the shape of a baguette, the size of the Eiffel Tower, and the color of the bright red strawberries in the markets (López-Aranda et al., 2009). In an attempt to try to decode this part of the brain, researchers have been looking at this part of the cortex to determine which neurons do what. Certain neurons in layers of this cortex have been tested, such as the layer 3 neurons playing a part in visual processing; however, the function of layer 6 neurons in this area remained a mystery (López-Aranda et al., 2009). In a recent study, López-Aranda and associates took on the challenge of determining the function of these neurons in the 6th layer of this part of the visual cortex (López-Aranda et al., 2009). The researchers hypothesized that these neurons play a role in ORM (López-Aranda et al., 2009).

To determine the function of neurons in layer 6, López-Aranda and associates set up an experiment where rats would have the opportunity to recognize objects they had seen before (López-Aranda et al., 2009). The experimenters placed two identical objects with the rats for three minutes, then they removed the items (López-Aranda et al., 2009). Later, during testing sessions at different timepoints, the rats had the opportunity to explore one of the old items and a new item that they had never seen (López-Aranda et al., 2009). The amount of time that the rats spent around each of the objects, old and new, was measured (López-Aranda et al., 2009). If the rats spent a great deal of time around the new item and ignored the old item, the researchers concluded that the rats remembered the old item using ORM, and they would rather use their time to explore the novel item (López-Aranda et al., 2009). If the rats spent an equal amount of time around the old and the new item, then the rats did not remember the old item and spent time examining both the new and the old items (López-Aranda et al., 2009).

The normal rats were able to remember the old object for 45 minutes, but not for 60 minutes (López-Aranda et al., 2009). When the researchers inserted more RGS-14 genes, which produces a regulator of G-protein signaling protein, into layer 6 neurons of the V2 cortex three weeks before the ORM testing, the rats remembered the object for at least 24 weeks (López-Aranda et al., 2009). With more of the RGS-14 protein in these neurons, the rat’s had longer ORM (López-Aranda et al., 2009). To make sure that this ORM enhancement was unique to this combination of RGS-14 protein in the layer 6 V2 neurons, this protein was overexpressed in three other brain locations and there was no significant ORM increase (López-Aranda et al., 2009).

Further proving their point, López-Aranda and associates killed off the neurons in layer 6 of V2 with the hypothesis that this would hinder ORM (López-Aranda et al., 2009). At 45 minutes, the rats with the missing neurons did not spend more time around the new object; they couldn’t remember that they had seen the old one before (López-Aranda et al., 2009). Just to make sure that the ORM ability was unique to V2 layer 6 neurons, neurons in other structures were eliminated (López-Aranda et al., 2009). These eliminations did not change the rats’ ORM ability to remember the old object (López-Aranda et al., 2009). Based on these data showing that increased RGS-14 protein expression in layer 6 neurons of V2 increases ORM memory, and elimination of the layer 6 V2 neurons decreases ORM memory, the experimenters wondered if these neurons were important for ORM memory formation or if they were the sites where the ORM memories were stored (López-Aranda et al., 2009).

In one more experiment, rats that had increased RGS-14 protein in the layer 6 neurons of V2 were exposed to new objects (López-Aranda et al., 2009). After that, the neurons in this layer were destroyed (López-Aranda et al., 2009). The rats had some ability to recall the objects that they had previously seen, but if they were exposed to objects after the neurons were destroyed, they could not remember them at all (López-Aranda et al., 2009). This experiment shows the importance of V2 layer 6 neurons in acquiring the memory, but because the rats remembered the old objects they had seen before the neurons were destroyed, this memory could not have been stored in the V2 layer 6 neurons (López-Aranda et al., 2009). While the V2 layer 6 neurons may not house the memories that allow you to recognize objects, they are important in being able to form the memories so you can recognize the French flags and the people in Monet’s painting (López-Aranda et al., 2009).

To wrap up this post, your visual system is even more amazing than just being able to sense the brushstrokes and colors when you look at the impressionist paintings in the Musée d’Orsay. Parts of it have to do with making memories of what you have seen, so that you can apply them to your future experiences. The brain is just like the deep ocean or distant space; we are figuring it out, but so much remains unknown. This study shows that the visual system is involved with more than just processing visual information. Just like in Monet’s painting where the lines that define the objects are blurred, the functions of the visual cortex seem to be unclear as it is is implicated for other things besides vision, like ORM.

Works Cited

López-Aranda, M. F., López-Téllez, J. F., Navarro-Lobato, I., Masmudi-Martín, M., Gutiérrez, A., Khan, Z. U. (2009). Role of layer 6 of V2 visual cortex in object recognition memory. Science 325:87-89.

Winters, B. D., Saksida, L. M., Bussey, T. J. (2008). Object recognition memory: neurobiological mechanisms of encoding, consolidation, and retrieval. Neuroscience and Biobehavioral Reviews 32:1055-1070.

Picture Citations

https://commons.wikimedia.org/wiki/File:Monet-montorgueil.JPG

http://commons.wikimedia.org/wiki/File:Musée_d’Orsay.jpg

http://commons.wikimedia.org/wiki/File:7e_arrondissement_paris.JPG

The Musée d'Orsay is located in the top right hand corner of this map of the 7th arrondissement in Paris

 ~ by Emily Aidan Berthiaume

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