Have you ever stepped out into the sun after a long day of sitting inside and suddenly felt the urge to sneeze?

Usually, sneezing is caused by irrigation in the nose, but how does the sun irritate your nose? This phenomenon is called the photic sneeze reflex. The cross-wire between the visual pathway and the sneezing pathways of your brain and nose could be caused by the sudden exposure to bright light.

This has also recently been named the ACHOO syndrome and has been seen in some genetically predisposed families. It is a polygenic trait that has been seen on the ZEB2 regions of chromosome 2 and 3. This area is involved with the development of the nervous system so any changes will cause the cross-linked reaction that we see in the ACHOO syndrome. Robust associated at these locations also indicate that the mutation is seen across multiple populations and ethnic groups.

Overall, the sun doesn’t directly “cause” you to sneeze, but rather triggers a chang within the visual and trigeminal response pathway. We still do not know how light can become a sneeze signal so quickly, especially considering this is not the average path for light input in the nervous system. Is the cortex driving this system or simply modulating it?

 

There is still so much more to learn about this reflex. Keep this in mind next time you step outside and feel your nose start to twitch!

 

 

References

Songu, M., & Cingi, C. (2009). Sneeze reflex: facts and fiction. Therapeutic Advances in Respiratory Disease, 3(3), 131-141.

Whitman, B. W., & Packer, R. J. (1993). The photic sneeze reflex: literature review and discussion. Neurology, 43(5), 868-868.

 

https://www.procreo.jp/labo/labo13.html

Watch this video. Do you see the dancer turning to the left?

Keep watching. Now, do you see her turning to the right?

The spinning dancer illusion has stumped viewers for years. Is the dancer actually changing directions, or is it just your brain playing tricks on you?

This video was made by a Japanese web designer named Noboyuki Kayahara in 2003 (Lucafò et. al. 2016).

Previously, I have talked about the concept of an image being multistable/bistable. Similar to images, this video can also be perceived as bistable because your brain can perceive the dancer as spinning in both the clockwise (CW) and counterclockwise (CCW) directions. Your brain maintains only one direction until prompted to switch because it settles on one interpretation until more evidence is accumulated to push it to change. In this case, my prompting you to look again would be sufficient evidence for your brain to look for a different visual interpretation of this video (Lucafò et. al., 2016).

In a study conducted by Bernal, it was found that a different hemisphere of the brain is activated for each iteration of the video (CW and CCW). This shows that different brain states are present for the subjective perception of a visual input. These differences in perception reflected spontaneous brain fluctuations in top-down sensory processing (Bernal et. al, 2014).

The ability of the brain to “flip” an interpretation of a visual input is a topic that has only been researched in recent years. The spinning dancer illusion is a simple and easy to measure and provides a strong basis for future studies in neural perception and attention.

References

Bernal, B., Guillen, M., & Marquez, J. C. (2014). The spinning dancer illusion and spontaneous brain fluctuations: An fMRI study. Neurocase, 20(6), 627-639.

Lucafò, C., Marzoli, D., Prete, G., & Tommasi, L. (2016). Laterality effects in the spinning dancer illusion: The viewing‐from‐above bias is only part of the story. British Journal of Psychology, 107(4), 698-709.

 

Yanny or Laurel? The Sound that Divided the Internet

One chaotic week in 2018, the internet was torn apart by one singular audio clip. Two syllables, repeated over and over, sparked worldwide confusion. I was a voice saying “Yanny” or “Laurel”. If you ask me, I heard Yanny on my first listen, but now I can easily switch between the two (unlike the dress mentioned in one of my previous posts). I am here once again to talk about how the same audio can be interpreted differently by ears around the world, the same way one picture of a dress can be interpreted differently by eyes around the world.

In my article about “The Dress,” I related the function of our visual system to a camera. I clarified that the eyes do not record everything like a camera, but use context and past experience to interpret visual cues. Similarly, our ears do not hear everything like a microphone. They interpret input based on frequencies and expectations, which can also change as we age.

Hearing isn’t always believing.

Sound waves are interpreted by entering the eardrum, travelling to the inner are, and activating hair cells. The auditory cortex in your brain constructs what you hear based on the activation patterns of your hair cells, past experiences, and the sensitivity of your ears, all of which can differ from each individual (Moore 2012).

When people hear different words in the audio clip, it is caused by the brain forming different perceptions of the same signal, not personal preference.

The Science Behind It

The audio clip contains a mixture of frequencies. When analyzed, it was found that there were frequencies at both the low range (400-500 Hz) and high range (2500-300 Hz) in the audio clip (Rosen 2018). People who hear “Laurel” tend to emphasize lower frequencies, while people who hear “Yanny” tend to emphasize high frequencies (Rosen 2018). This is similar to “The Dress,” where people who saw each color set had a different preference for color undertones.

Presbycusis is a phenomenon that causes people to lose sensitivity to upper ranges of audio frequency as they age, causing a physical variation in how people hear (Gates et. al., 2006). Since “Yanny” is encoded in high-frequency sounds, it is more likely for it to be heard by younger people (like me!).

Surveys have shown that it was more likely for older adults to hear “Laurel” due to its lower frequencies. These frequencies are more stable throughout one’s lifespan.

Why does the brain choose one word over the other?

Top-down processing is when the brain uses existing knowledge and experience to interpret sensory information, instead of letting the sensory information motivate the interpretation. This type of processing is important for interpreting ambiguous sounds such as this one (Hickok & Poeppel, 2007). If your brain is used to certain vowels or speech patterns, you may hear a specific word. For example, more American English speakers heard “Laurel” because the low-frequency format is common in American English, while listeners who spoke a language with a higher-frequency format were more likely to hear ‘Yanny’ (Samuel, 2011).

What does this reveal?

Our brain does not perceive all the senses the same way as everyone else! Hearing sounds that are ambiguous forces our brain to guess, and not all brains guess the same way.

References

Gates, G. A., & Mills, J. H. (2005). Presbycusis. The Lancet, 366(9491), 1111–1120. https://doi.org/10.1016/S0140-6736(05)67423-5

Hickok, G., & Poeppel, D. (2007). The cortical organization of speech processing. Nature Reviews Neuroscience, 8(5), 393–402. https://doi.org/10.1038/nrn2113

Moore, B. C. J. (2012). An introduction to the psychology of hearing (6th ed.). Brill.

Rosen, J. (2018). The science behind Yanny vs. Laurel: Why we hear what we hear. The Journal of the Acoustical Society of America, 144(1), 62. https://doi.org/10.1121/1.5052025

Samuel, A. G. (2011). Speech perception. Annual Review of Psychology, 62, 49–72. https://doi.org/10.1146/annurev.psych.121208.131643

 

 

 

The Dress that Broke the Internet

I’m sure everyone has heard of this dress before, right? If you are not familiar, the picture of this dress went viral a few years ago because everyone on the internet could not agree whether it was blue and black or white and gold in color. If you ask me, I would say I see white and gold. How is it possible that we all look at the same picture but see completely different colors?

Seeing isn’t always believing

But why is this true? Why is everyone seeing this picture differently? Instead of recording the world like a camera, our brain actively interprets what we see using light, context, and past experiences (Foster 2011).  I’m here to talk about the neuroscience behind perceptions and why different people see different colors in the same picture.

Battle of the Brain

Studies have shown that there are stark individual differences in how people see color (Lafer-Sousa  2015). For example, how I define “red” is not the same way you define “red.” One specific study looked at which wavelengths of light were recognized in people who looked at the picture of the dress. People who prefer a more illuminating light, like a blue sky, saw white and gold because they were recognizing shorter wavelengths of light. On the other hand, people who favor warm light see blue and black because they see the longer wavelengths of light (Lafer-Sousa 2015).

Can you see it both ways?

Now that you know that people see both color schemes, are you able to see the other one? Personally, I am only able to see white and gold. Other people can switch between white & gold and blue & black. The quality of being able to switch between your perceptions is called a multistable image. Most of the people who are able to switch between the two color schemes in this picture have a background in art, so they are well-experienced in different color perceptions (Lafer-Sousa 2017).

References

Foster, D. H. (2011). Color constancy. Vision Res, 51(7), 674–700. https://doi.org/10.1016/j.visres.2010.09.006

Lafer-Sousa, R., Hermann, K. L., & Conway, B. R. (2015). Striking individual differences in color perception uncovered by ‘the dress’ photograph. Current biology : CB, 25(13), R545–R546. https://doi.org/10.1016/j.cub.2015.04.053

Lafer-Sousa, R., & Conway, B. R. (2017). Journal of Vision, 17(2), 25. https://doi.org/10.1167/17.2.25