Author Archives: Sarah Strausser

Bonjour, Do You Speak English?


If you asked me what the hardest thing about living in Paris has been, my answer would be simple – the language barrier. Before leaving for Paris, I didn’t know any French besides how to say hello and goodbye. While I have picked up a few useful phrases in the past 4 weeks, it has still been very difficult to remember what I’ve learned. I began to wonder why I was having such a hard time with French, especially based on my previous experiences with language. When I was a young child, my mother used to teach me Chinese words and phrases. While I am nowhere near fluent in Chinese, I can still easily remember names of words and recognize phrases that I learned many years ago. On the other hand, learning French has been quite the struggle. I can spend a while reading my French traveler’s guide and practice my accent, yet hardly remember what I practiced the next day. Language is a very important field in neuroscience, so this experience led me to ask several questions: Why is it more difficult to learn a second language as we get older? Are there differences in anatomy of language areas in the brain depending on what age you learned a second language? While it is generally well known that children are able to learn languages much more quickly than adults (Johnson et al., 1989), I wanted to look further into how the age of learning a second language affects brain structure.

In 2014, Klein et al. published a study that examined how the age at which a second language is learned shapes brain structure. This study used four groups of participants: monolinguals who spoke only one language (monolinguals), bilinguals who learned two languages either simultaneously from birth or up until age 3 (simultaneous bilinguals), bilinguals who learned their second language from early childhood ages 4-7 (early sequential bilinguals), and bilinguals who learned their second language during late childhood ages 8-13 (late sequential bilinguals). All participants were interviewed and given questionnaires about their language background to determine which group they belonged to. It’s important to know that monolinguals were considered fluent only in their native language even if they received some formal training of another language, so taking a few years of Spanish in school doesn’t count as being bilingual. This study used magnetic resonance imaging scans (MRI), which allowed researchers to take an image of the brain and compare anatomical differences between participants’ brains.

Image: Cerebral Cortex, the outer layer of tissue in the brain that researchers measured for thickness

Animation: Inferior Frontal Gyrus Location (left side)

First, researchers tested for general differences in cortical thickness (how thick the outer layer of tissue in the brain was) using MRI between monolinguals and the different groups of bilinguals. They were interested in measuring cortical thickness to see exactly how being bilingual affects growth in language areas of the brain during development. A thicker cortex meant that there was more neuronal (cells in the brain) development in that brain region. Researchers found that there was a significant difference in cortical thickness between the groups in a brain region called the left inferior frontal gyrus (LIFG). The LIFG is very important for phonological and syntax processing in language (Vigneau et al., 2006). Phonological processing means using sounds to understand language, and syntax refers to understanding the order of words to form sentences. Researchers found that the LIFG was much thicker in the early and late sequential bilingual groups compared to the monolingual group. Put more simply, the LIFG was much thicker only in bilinguals that learned their second language after early childhood compared to monolinguals. These differences in cortical thickness were not surprising, since the LIFG is a key brain area involved in language processing. These results demonstrated that learning a second language after becoming fluent in the first language changes brain structure during development. This was very significant finding, because it shows the “plasticity” of the brain, or the brain’s ability to reorganize itself and form new connections in different environments! To explain why the cortex becomes thicker in early and late sequential bilingual groups, researchers suggested that learning a second language after early childhood causes neurons and connections between neurons to grow in brain areas involved in language.

Figure 1: Klein et al., 2014

MRI scans showed that there was no difference in cortical thickness between the monolingual group and the simultaneous bilingual group. This was another very important finding, because it showed that being bilingual only affects brain development when a person learns their second language after early childhood. Researchers reasoned that these differences in cortex thickness might mean that there are different learning processes involved in first and second language learning only when the languages are learned separately after early childhood. These different learning processes might cause the cortex in language areas to become thicker as neurons and their connections grow. These results also show that the age when learning a second language is very important for setting up the brain structures involved in language.

Neurons and their many connections

Once researchers determined general differences in cortex thickness between monolinguals and bilinguals, they wanted to further study the relationship between brain structure and age of language learning in the bilingual participants. They found that the later a second language was learned after an individual learned their first language, the thicker the cortex was in the LIFG. Based on these results, researchers suggested that that the thicker cortex associated with later second language learning might reflect the brain using less than optimal neural circuits for language learning. An easier way to think about the brain is by thinking of it as a huge switchboard with lots of connections between each area of the brain. A neural circuit is like a path that information follows to get from one part of the brain to another. There are neural circuits that are direct and very quick, but there are also more roundabout ways to send information from one area to another. As we mature, our brain begins to solidify its connections, so the neural circuits used when a second language is learned at a later age may not be as direct and quick. Using suboptimal circuits could contribute to the cortex becoming thicker, as neurons increase their connections to follow a roundabout path. Learning both languages at the same time during early childhood appeared to use optimal neural circuits for language learning, because there were no differences in thickness between monolinguals and simultaneous bilinguals.

I found this study to be very interesting because it showed that there are anatomical differences in language regions of the brain that depended on what age a participant learned their second language. It was also very informative because it shows that the brain isn’t a set in stone structure, and our environment can significantly contribute to our development. As a follow up for more concrete conclusions about neural circuits involved in language learning, I’d like to see a study where researchers measure activation of the LIFG rather than just differences in cortex thickness. For example, functional magnetic resonance imaging (fMRI) measures brain activity by detecting blood flow to specific brain regions. Participants could read or listen to their native language followed by their second language in an fMRI machine to measure and compare how much language areas of the brain are active. Results from this would be even more informative in understanding how the age at which a second language is learned plays a role in language processing. For example, variation in brain activity could confirm differences in optimal and suboptimal neural circuits depending on what age the second language was learned. This would allow researchers to understand more about how neural processing, rather than just anatomy, is affected in language areas by learning a new language.


Until next time,

  • Sarah



Johnson JS and Newport EL (1989). Critical period effects in second language learning: The influence of maturational state on the acquisition of English as a second language. Cognitive psychology, 21(1), 60-99.

Klein D, Mok K, Chen JK, & Watkins KE (2014). Age of language learning shapes brain structure: a cortical thickness study of bilingual and monolingual individuals. Brain and language131, 20-24.

Vigneau M, Beaucousin V, Herve PY, Duffau H, Crivello F, Houde O, and Tzourio-Mazoyer N (2006). Meta-analyzing left hemisphere language areas: phonology, semantics, and sentence processing. Neuroimage30(4), 1414-1432.

Cerebral cortex image (Creative Commons):

Left inferior frontal gyrus animation (Creative Commons):

Neural connection image (Creative Commons):

French Phrasebook Image:,204,203,200_.jpg

Figure 1 from Klein et al., 2014

There’s Nothing Like the Smell of Home

Photo of the metro

About two weeks ago, I arrived very jet-lagged in Paris and couldn’t wait to explore the city. I wanted to take it all in – the sights, the sounds, and the smells. We hit the ground running during our first evening in Paris and rode the metro to the Eiffel Tower. As we waited in the metro station, I realized that I recognized the exact smell of the station. The dusty, metallic smell of the metro brought back many fond and vivid memories during my childhood where I often rode the metro in Toronto. I began to wonder why the smell of the metro brought back such vivid, emotional memories that happened over 10 years ago.

Balls at the museum that emitted smells when you picked them up!

Fast forward to several days ago, I experienced something similar in the Musée du Parfum (perfume museum). It is an amazing museum that is filled with lots of perfume and strong scents that we were able to sniff! One of the scents that stood out to me smelled just like a campfire. Similar to my metro experience, the strong smell of the burning wood brought back many great memories of roasting marshmallows around a bonfire at camp every year.

Fragrant roses at the museum



In the courses that I’ve taken as an NBB major, I have learned about the separate pathways in the brain that are active during olfaction, memory retrieval, and certain emotional responses. Interestingly, I have not yet learned what happens when those pathways interact like when an emotional memory is retrieved from an odor. I wanted to delve deeper and learn more about what is happening when memories and emotions are retrieved from odors.

Olfactory Pathway Diagram


It is already known that olfaction, memory, and emotion are closely linked in the brain. An olfactory signal is transmitted from the primary olfactory cortex to the amygdala and the hippocampus before being sent to higher order olfactory cortices (Shipley and Reyes, 1991). The amygdala is generally associated with emotional responses, while memory processes are closely linked to the hippocampus (Fortin et al., 2004; Cardinal et al., 2002). So, the olfactory signal is relayed through two brain structures that are important for both emotion and memory. 

In 2014, Saive et al. published a study that sought to better understand the interaction between emotion, olfaction, and memory. They tested the hypothesis that emotions invoked by odors facilitate the memory of specific unique events. To do this, they created a model to study memory and mimic real-life situations as best as possible in humans. Participants explored three laboratory episodes, each consisting of three unfamiliar odors (what), positioned at three specific locations (where), within a specific visual environment (which context). Participants explored one episode per day for three days, which they called encoding days. On the 4th day, called retrieval day, they were tested with distractor odors and the odors that they had previously experienced. The distractor odors were used to make sure that participants were associating the correct smells with their memory. Participants were asked to push a button if they recognized the smell, and then had to choose the specific location that they experienced the odor and the correct visual context. They also rated the odors based on pleasantness to investigate the influence of emotion on memory performance.

This study had several important findings that helped researchers better understand what was going on when participants retrieved memories from specific odors. First, they found that the number of accurately remembered contexts and locations was significantly higher when the odors were more pleasant or more unpleasant than neutral. This suggests that the intensity of the emotion  and the distinctness of the smell (but not pleasantness vs. unpleasantness) enhanced memory retrieval. This is what they expected to see – we are more likely to associate a memory that has emotional context with an odor than a neutral smell that we might experience every day.

Measured response times showed that the more information the participants remembered about an episode (what, where, which context), the faster they answered. Interestingly, the time period between odor recognition and retrieving details about their experience was constant no matter how accurate their retrieval was. Since there was no response time difference observed, researchers suggested that after odor recognition participants immediately recalled the whole episode at once rather than in pieces. Put simply, participants didn’t go step-by-step in their memory to recall where there were or how they were feeling, they instead remembered the entire memory at once. This led the researchers to propose a model to explain the cognitive processes that are involved in this unique memory retrieval. This model states that recognizing an odor and retrieving details about the memory associated with the odor are combined into a simultaneous memory retrieval process that begins as soon as an odor is smelled.

One strength of this study is that it mimicked real-life scenarios in the laboratory as naturally as possible by allowing participants to freely explore contexts with unique odors and ranging emotional valences. This makes the model suggested by the researchers more relevant to life outside of the laboratory and helps us better understand how odor is closely tied to memory recognition. Now I understand why I was able to quickly retrieve memories from so long ago just from a smell. Maybe many years from now, the smell of fresh baked bread will bring back fond memories of the many boulangeries (bakeries) I visited during my time in Paris.




Cardinal, R. N., Parkinson, J. A., Hall, J., & Everitt, B. J. (2002). Emotion and motivation: the role of the amygdala, ventral striatum, and prefrontal cortex. Neuroscience & Biobehavioral Reviews26(3), 321-352.

Fortin, N. J., Wright, S. P., & Eichenbaum, H. (2004). Recollection-like memory retrieval in rats is dependent on the hippocampus. Nature431(7005), 188-191.

Saive, A. L., Royet, J. P., Ravel, N., Thévenet, M., Garcia, S., & Plailly, J. (2014). A unique memory process modulated by emotion underpins successful odor recognition and episodic retrieval in humans. Frontiers in behavioral neuroscience8, 1-11.

Shipley, M., & Reyes, P. (1991). Anatomy of the human olfactory bulb and central olfactory pathways. In The human sense of smell (pp. 29-60). Springer Berlin Heidelberg.

Images: – Olfactory pathway diagram – Metro photo, Creative Commons

Photos at the museum – taken by myself