Tag Archives: Versailles

Lost in the gardens of Versailles

Like a lot of students, I used this past weekend as a chance to visit places easily accessible from Paris. On Saturday, Jamie, Genevieve, and I boarded the RER-C and headed to see the Château de Versailles. We went straight to the gardens, a gorgeous, intricate maze of hedges filled with sculptures and fountains. After aimlessly wandering far into the gardens, we heard classical music playing. We knew that it must have been the soundtrack to one of the weekend fountain shows, when the flow of water is set to follow the rhythm of music.

Map of the palace and gardens of Versailles

Just moments after the music started playing, we managed to find our way to the fountain show just by following the sound of the music. The water spouted and spun to the rhythm of the music and the slight mist was refreshingly cool in the middle of a hot summer day. Later that day, I was fascinated by how we managed to find the fountain show based only on the sound of the music. We had never been to the gardens before, we did not have a map, and we did not even know where we were going.

The fountain show

While it is often unconscious, determining where a sound is coming from is a remarkable ability. Figuring out where a sound originates can help us with everything from avoiding oncoming traffic to turning towards our friends in a crowded room (Dobreva et al., 2011; Middlebrooks JC, 2015). Part of this ability comes from having two ears because we can decide which direction a sound is coming from by comparing what we hear in our left and right ears (Joris and Yin, 2007).

However, in our daily lives, there are a lot of hidden challenges that make this task harder. Sound waves from a single source bounce off people and objects and ultimately hit our ears from several angles and directions.Both the unhindered sound itself and the reflections of that sound eventually reach our ears. The sound itself is known as the lead because, since it follows the most direct path, it hits the ear first (Brown et al., 2015). The ability to respond to the lead and not the subsequent reflections of that sound (the lags) is known as the precedence effect (Wallach et al. 1949).

The precedence effect is crucial for the accuracy of our sound localization. As we walked through the gardens of Versailles our ears were struck by soundwaves from both the music itself and reflections of the music bouncing off the greenery. The precedence effect is what allowed us to fuse these sounds together and find the fountain show rather than accidentally ending up at a tree the music had bounced off.

While theories about the precedence effect have been around for decades, the biological mechanisms underlying it were still unclear. Some scientists argued that this effect occurred within the brain while the sounds were being processed through synaptic inhibition (Pecka et al. 2007; Xia et al. 2010). Synaptic inhibition is when interconnected neurons send excitatory and inhibitory signals to amplify certain information (here, the lead sound) and depress other information (the lagging sounds).

Other scientists have argued that the effect could be a mechanical result of the cochlea, the inner ear where sounds are converted to electrical signals. These researchers note that once the lead hits the cochlea that sound continues to resonate. They contend that the lag cannot be communicated as strongly because the cochlea is still passing information about the lead (e.g. Bianchi et al., 2013).

In the past, there was limited evidence to supported one of these ideas over the other because it is technically difficult to impair the auditory structures of the ear or the auditory areas of the brain without impairing both. In their recent work, Brown et al. examined these theories by comparing normal hearing subjects to deaf subjects with cochlear implants, which directly stimulate the brain in response to sound. These deaf subjects had two implants and could still perceive sounds on either side of them but did not have functioning cochlea.

A cochlear implant

The researchers exposed subjects to lead-lag pairs of stimuli that mimicked a sound and the reflection of that sound. They asked subjects to indicate if they heard one sound or two and where the sound(s) originated. In normal hearing subjects these pairs were acoustic clicks. In deaf patients, they were electrical impulses sent directly into the cochlear implants. To measure the precedence effect, the researchers measured the subjects’ ability to recognize the two stimuli as one sound (termed “fusion”) and to determine the origin of the sound (“localization dominance”).

The authors found that both normal hearing and deaf patients could fuse the paired stimuli together and perceive them as one sound, although this ability was marginally weaker in the deaf patients. Furthermore, while there were idiosyncratic differences between individuals, whether subjects had cochlear implants did not affect their ability to determine the origin of sounds. This study presents evidence that people without cochlea can demonstrate the precedence effect at about the same levels as people with normal hearing. Since this effect can be seen in subjects without cochlea, this effect cannot be due to the mechanical features of the cochlea. This suggests that features of auditory neurons can account for the precedence effect that allows us to accurately localize sound.

This was a clever study but of course it is important to remember that it is not conclusive. There were small differences in deaf subjects’ ability to fuse the stimuli into a single sound, which could indicate that the cochlea at least contributes to the precedence effect. Also, mechanical aspects of structures beside the cochlea could be crucial. While this study is not conclusive it does highlight the importance of synaptic inhibition. This provides a launching pad for the continued study of the biological mechanisms underlying the precedence effect, which could help with everything from more immersive virtual reality to better treatment for hearing loss.


Bianchi F, Verhulst S, Dau T (2013). Experimental evidence for a cochlear source of the precedence effect. Journal of the Association for Research in Otolaryngology JARO, 14(5):767–779.

Brown AD, Stecker GC, Tollin DJ (2015) The Precedence Effect in Sound Localization JARO, 16(1): 1-28

Brown AD, Jones HG, Kan A, Thakkar T, Stecker GC, Goupell MJ, Litovsky RY (2015). Evidence for a neural source of the precedence effect in sound localization. Journal of neurophysiology 114(5): 2991–3001

Dobreva MS, O’Neill WE, Paige GD (2011). Influence of aging on human sound localization. Journal of neurophysiology, 105(5): 2471–2486

Joris P, Yin TCT, (2007) A matter of time: internal delays in binaural processing, Trends in Neurosciences, 30(2): 70-78

Middlebrooks, JC (2015) Chapter 6 – Sound localization, Handbook of Clinical Neurology, 129: 99-116.

Pecka M,  Zahn TP, Saunier-Rebori B, Siveke I,  Felmy F, Wiegrebe L,  Klug A, Pollak GD, Grothe B (2007) Inhibiting the Inhibition: A Neuronal Network for Sound Localization in Reverberant Environments Journal of Neuroscience, 27(7):1782-1790

Wallach H, Newman EB, Rosenzweig R (1949) The precedence effect in sound localization. Am J Psychiatr 62:315–336

Xia J, Brughera A, Colburn HS, Shinn-Cunningham B (2010). Physiological and psychophysical modeling of the precedence effect. Journal of the Association for Research in Otolaryngology : JARO, 11(3), 495–513


Cochlear Implant: “Ryan-Funderburk-1.jpg” by Rfunderburk90 is licensed under CC PDM 1.0

Sorbet, what have you done to me?

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


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.