Categories
Neuroscience

The Inferior Temporal Cortex “Recycled” to Aid Reading

Abstract

One of the many strengths of humans is the ability to create and understand intricate languages of reading and writing. Scientists have long debated how humans’ brains have developed these reading and writing specific skills in such a short time.  Neuroscientists’ recent study from Massachusetts Institute of Technology, however, has unveiled that rather than our brains evolving to perform linguistic functions, the inferior temporal cortex (IT cortex) has been “recycled”.  In functional magnetic resonance imaging (fMRI) research, a region within the IT cortex known as the visual word form area (VWFA) lightens when the brain recognizes orthographic stimuli, in this case, words.  Additionally, researchers used fMRI to find that areas of the IT cortex meant for face and object recognition lit up distinguishing words after learning to read. This shows that the human mind is adaptable and can repurpose itself for different tasks, and in this case, for reading.

Experiment

To test this theory, Old-World monkeys, such as baboons and rhesus macaques, which diverged from humans about 25 million years ago, were studied.  Despite not being perfect models for the human mind, these primates have enough similarities to be comparable.  Research has shown that we share similar functions and structures in the ventral visual pathway which is a section of the brain utilized for object recognition. In prior research from 2012, baboons were able to differentiate real English words and nonsensical combinations of letters or non-words with enough training.  This proves that word recognition is something that does not require years of evolution and a complex understanding of linguistics.  However, researchers still pondered the neural workings behind this skill.  

This curiosity led to a new test, where scientists used microelectrode arrays to record the neural activity in untrained macaque monkeys while they examined both words and non-words.  These arrays were placed in the monkeys’ IT cortex as well as a part of their visual cortex called V4, which connects to the IT cortex.  Then, they put the data into a linear classifier, a computer model designed to identify whether or not words triggered neural activity in the monkeys.  Dr. Rishi Rajalingham, the lead of this study, explained that this process is very effective and easy, because there is no training necessary for the monkeys.  

Data

In this diagram, Model A presents an example of text the macaque monkeys would view, a visual of the IT cortex, and V4 lighting up.  On the right, the figure shows which orthographic tests affect which specific neurons using data from the microelectrode arrays.

Model B displays three different sets for the monkeys.  The first contains samples of words and random assortments of letters, and the second tests the variation in the size and spacing of the words. The third set displays one letter but each card has the letter in different locations.  

Model C presents the location of the microelectrode arrays in 4 example monkeys: N, S, B, and M.  To the right are 8 different graphs representing example IT sites, each with some of the monkeys’ neuronal response to a set of 5, consisting of both words and a random string of letters.  The colors of the data show the intensity of the response with blue being the lowest and red being the highest.  In addition, there is shading around some sections of the data that represents the general margin of error.  Over the 300 millisecond time frame, many of the words sparked higher responses in the monkeys compared to the jumbled letters despite having no prior training or experience with orthographic stimuli.  

The model displayed that the data corresponding to the IT cortex was about 70% accurate, with both performance and errors made by these monkeys similar to the baboon study in 2012.  Meanwhile, the visual cortex was notably less accurate which reveals that the skilled areas of the IT cortex for object recognition are specifically capable of being remodeled if needed for reading.  These observations reveal that the IT cortex in untrained monkeys is sufficient enough to complete simple orthographic tasks such as word recognition.  In the future, researchers plan on studying both trained monkeys and literate humans to compare results. With adequate training, our brains are capable of learning to read without highly evolved brains and by “recycling” our IT cortex.

References

The inferior temporal cortex is a potential cortical precursor of orthographic processing in untrained monkeys, Nature Communications, August 2020 

https://www.nature.com/articles/s41467-020-17714-3

“Parts of the human brain have been ‘recycled’ for reading, indicates study”, News Medical Life Sciences, August 2020

https://www.news-medical.net/news/20200805/Parts-of-the-human-brain-have-been-e2809crecyclede2809d-for-reading-indicates-study.aspx

“To read, humans ‘recycled’ a brain region meant for recognizing objects”, United Press International, August 2020

https://www.upi.com/Science_News/2020/08/04/To-read-humans-recycled-a-brain-region-meant-for-recognizing-objects/8801596564675/

“Key brain region was ‘recycled’ as humans developed the ability to read.”, MIT News, August 2020

http://news.mit.edu/2020/brain-recycled-ability-read-0804

Orthographic Processing in Baboons (Papio papio), Science, April 2012

https://science.sciencemag.org/content/336/6078/245.abstract

Kyle Phong, Youth Medical Journal 2020

Categories
Health and Disease

How Pesticides Increase the Transmission Rate of Schistosomiasis 

Both pesticides and fertilizers have had their dark history of harming the environment, yet it is still commonplace today.  The continuous usage of agrochemicals carries far more unintended consequences than we expected.  Recent discoveries from the University of California, Berkeley research team has revealed that the rising water developmental projects such as dams have allowed a rise in the freshwater snail population, while dispersing its predators which are necessary for keeping its numbers in check.  In addition, agrochemicals we utilize today are polluting the environment, therefore increasing our exposure and vulnerability to infectious diseases, particularly schistosomiasis.  

What is Schistosomiasis?

Schistosomiasis, known as bilharzia or snail fever, derives from parasitic worms (In this case, Schistosoma haematobium) in tropical and subtropical freshwater environments.  This disease earned the moniker “snail fever” due to the schistosome parasites’ use of snails as their hosts.  As a result, the freshwater becomes contaminated, when humans make contact with these waters parasites burrow into their bodies.  The worms travel through the bloodstream to vital organs such as the liver, kidney, and intestines.  Meanwhile, females lay their eggs which are passed through human urine and feces.  If these excretions reach freshwater sources, they will repeat the process to inhabit snails and grow before infecting another human. Without this trend, the parasitic eggs remain in the body and are attacked by the immune system.  There are different symptoms as they pertain to the infected area.  For example, one might experience seizures, headaches, and loss of balance if their nervous system is infected.  If not treated properly, short-term or acute schistosomiasis can lead to long-term or chronic schistosomiasis.  In this state, females will continue to reproduce and infected organs can be critically damaged.  

Findings

Researchers have found that the utilization of agrochemicals has accelerated the transmission process of schistosomiasis.  Some effects of agrochemical pollution include eliminating snail predators, increasing algae which are a main food source for the snails, as well as impacting the schistosome parasites’ survival directly.  The insecticides, chlorpyrifos, and profenofos are toxic to the predators that hunt these snails which allows the freshwater snail population to increase dramatically, activating a top-down trophic cascade.  Atrazine, an agricultural herbicide, was discovered to indirectly aid the growth of the algae which these snails consume, causing a bottom-up trophic cascade.  The snail population expanded, allowing more snails to serve as intermediate hosts for the parasites. Sub-Saharan Africa, where over 90% of schistosomiasis cases originate, has been exponentially increasing its application of agrochemicals in hopes for efficient and less arduous methods of farming.  With an ever-increasing freshwater snail population, the waterborne parasite population grows as well, resulting in a rise in the human infection rate.

This diagram from The Lancet Planetary Health shows the use of different agrochemicals and their effects in relation to the study.

In addition, researchers input their data into a complex mathematical model in order to have a general form of structure for the situation.  Then, they could easily approximate the R0 (basic reproduction number) of the schistosomes.  The R0 of S haematobium was about 1.65 while in an agrochemical-free environment.  However, the R0 has increased triple the amount when affected by agrochemicals.  The model was also capable of estimating the number of DALYs (disability-adjusted life-years) lost per 100,000 people from the altered schistosomiasis.  This represents about how many years are lost due to the disease they have.  It has been approximated that there have been 142 additional DALYs lost per 100,000 people.  By discovering the effects of individual chemicals within the pesticides, the research team could estimate both the R0 and DALYs that each caused.

Conclusion

This isn’t the first time we’ve witnessed the ramifications of using agrochemicals.  One notable instance was the widespread usage of the insecticide, DDT, which leaked into waterways, poisoning fish and other aquatic life.  When bald eagles consumed these toxic fish, they lost the ability to produce sturdy eggshells for their offspring.  As a result, the eggs often did not survive due to its lackluster protection which led to a massive decline in the bald eagle population.  

There are countless chemical compounds used in pesticides, all harboring dangerous side effects that can greatly impact the ecosystem.  Justin Remais, a leading figure in UC Berkeley’s School of Public Health, explains that reducing agrochemical pollution will not only reduce risk of schistosomiasis, but other infectious diseases as well.  Now that we know agrochemicals cause both unwanted direct and indirect effects, it is especially crucial that we find alternative methods to lower the risk of transmission by eliminating agrochemical pollution in regions where schistosomiasis is endemic.  

References

  • Effects of agrochemical pollution on schistosomiasis transmission: a systematic review and modelling analysis,The Lancet Planetary Health, July 2020

https://www.thelancet.com/journals/lanplh/article/PIIS2542-5196(20)30105-4/fulltext

  • “Schistosomiasis”, World Health Organization, March 2020

https://www.who.int/news-room/fact-sheets/detail/schistosomiasis#:~:text=Transmission%20occurs%20when%20people%20suffering,where%20the%20females%20release%20eggs.

  • “Pesticide use can speed the transmission of schistosomiasis”, News Medical Life Sciences, July 2020

https://www.news-medical.net/news/20200717/Pesticide-use-can-speed-the-transmission-of-schistosomiasis.aspx

  • “Schistosomiasis (bilharzia)”, National Health Service, November 2018

https://www.nhs.uk/conditions/schistosomiasis/