TORONTO, June 28, 2022 鈥� Tadpoles see well underwater, but what happens when they become frogs and live primarily on land? Researchers at 91亚色 and several other institutions, curious about the answer, found the eyes of tadpoles undergo a surprising number of changes.

It鈥檚 already known that tadpoles go through a physical metamorphosis on their way to becoming a frog, but what wasn鈥檛 known is how their vision adapts at a molecular level across the life stages to a strikingly different environment.

91亚色 Assistant Professor , who studies the visual system of vertebrates in the Faculty of Science, along with an international team of researchers, examined the eyes of southern leopard frogs to find out if and how they changed.

鈥淪eeing underwater is not the same as seeing on land. The light underwater can have more of a reddish cast, especially in ponds where many frogs live, while the light on land is bluer. The amount of light is also different under water versus on land. Animals that see well in one environment will likely not see clearly in the other. We were interested in finding out what changes occur that allow an animal to go from seeing underwater to seeing on land,鈥� says Schott, who led the study and is the corresponding author.

鈥淭he adaptive decoupling hypothesis proposes that animals that have distinct life stages separated by metamorphosis, like caterpillars to butterflies or tadpoles to frogs, might be more able to adapt to their different environments.鈥�

The researchers explored changes in gene expression in the eyes of leopard frog tadpoles and juvenile frogs using RNA sequencing, allowing them to see the levels of gene expression, or which genes were turned on in the eyes. They also used microspectrophotometry to measure whether the photoreceptor cells in the eyes were more sensitive to the redder or bluer parts of the light spectrum at different life stages. These photoreceptor cells send light signals through the retina to the brain and are what allows animals, including humans, to see.

What they found surprised them. 鈥淭he difference in the gene expression levels that we found in their eyes across the life stages was much higher than expected and a high proportion of them are genes that are directly involved in vision, which was an exciting result,鈥� says Schott.

They found 42 per cent of genes in the eyes of tadpoles changed, were differentially expressed, once it metamorphosized into a frog.

The team, including researchers from the Smithsonian Institution, Cornell University, The Natural History Museum in London, United Kingdom, the California Academy of Sciences, and the University of Texas at Arlington, also found the genes that control visual function and development, including spectral sensitivity and lens composition, changed the most.

The eyes of tadpoles had shifted and adapted to see better in a bluer light environment as they changed to a juvenile leopard frog 鈥� living and seeing on land 鈥� compared to the redder light environment of the freshwater habitat they live in as tadpoles.

The paper, , was published today in the journal BMC Biology.

-30-

91亚色 is a modern, multi-campus, urban university located in Toronto, Ontario. Backed by a diverse group of students, faculty, staff, alumni and partners, we bring a uniquely global perspective to help solve societal challenges, drive positive change and prepare our students for success. 91亚色's fully bilingual Glendon Campus is home to Southern Ontario's Centre of Excellence for French Language and Bilingual Postsecondary Education. 91亚色鈥檚 campuses in Costa Rica and India offer students exceptional transnational learning opportunities and innovative programs. Together, we can make things right for our communities, our planet, and our future.

Media Contact:
Sandra McLean, 91亚色 Media Relations, 416-272-6317, sandramc@yorku.ca

The post Tadpoles undergo surprising number of vision changes when becoming frogs appeared first on News@91亚色.

TORONTO, May 26, 2020 鈥� How does the brain determine what shade of colour our eyes are seeing? Vision researchers at 91亚色 have pinpointed the exact mechanism that allows the brain to do just that. In a study published in researchers at the Lassonde School of Engineering and the Center for Vision Research show how the brain can perceive a wide range of colours while being able to differentiate between, for example, magenta and lavender. There is still much debate on where and how in the brain such perceptions happen, but by creating a new mathematical model, researchers have found the brain achieves this by very simple calculations that use multiplication.

鈥淚f you鈥檙e looking at a particular shade of blue, is there somewhere in your brain that represents that blue? This study explains how the brain computes that blue and it gives you every step of processing in detail so that you can trace where things might go wrong,鈥� says John Tsotsos, a professor in the Department of Electrical Engineering and Computer Science at the Lassonde School of Engineering.

The study found that a simple processing聽framework not only furthers our understanding of colour processing in the brain but may also help in testing these mechanisms in individuals who have shown less accurate聽colour discriminations than individuals in a control group.

Researchers took all the previous mathematical and theoretical models of colour processing 聽鈥� including data on how animal neurons respond to colour 鈥� and added the new component of multiplicative modulation. Using physiological evidence, they computationally modeled neurons from different areas of the brain involved in colour processing. The model lays out the progression of the colour signal in the brain in a step-by-step manner. By using this approach, they were able to provide a more comprehensive understanding of colour perception than had been possible previously.

鈥淥ur network of neurons was required to comply with existing knowledge of brain color cells,鈥� says Paria Mehrani, a PhD student in Tsotsos鈥� Lab and lead author of the study.聽 鈥淪etting the properties of model neurons based on the statistics of some observed data could possibly result in cells with properties different from those of biological colour neurons. As a result, one could not have meaningful processes explaining the brain that way. In our model, however, certain colour processing aspects can be learned given data, especially in the last processing layer in our network. With such a model as foundation, machine learning can help further our understanding of other aspects of colour processing in the brain.鈥�

Furthermore, the research team suggested their model sheds light on a specific kind of neural interaction. This information could prove useful in explaining poor colour discrimination and provide a pathway to a remedy in the future.

The study may also help inform the building of machine vision systems which need to have this process in place, says Tsotsos. 鈥淚f you want to have as聽good colour discrimination as聽humans do, this study helps inform us on how to build that machine vision system.鈥�

Researchers say those working in the development of AI systems that rely on discrimination of pure colours could benefit from this information: for example, autonomous car systems and agricultural vision systems that rely on colour discrimination to determine ripeness of fruits and vegetables.

91亚色 champions new ways of thinking that drive teaching and research excellence. Our students receive the education they need to create big ideas that make an impact on the world. Meaningful and sometimes unexpected careers result from cross-disciplinary programming, innovative course design and diverse experiential learning opportunities. 91亚色 students and graduates push limits, achieve goals and find solutions to the world鈥檚 most pressing social challenges, empowered by a strong community that opens minds. 91亚色 U is an internationally recognized research university 鈥� our 11 faculties and 25 research centres have partnerships with 200+ leading universities worldwide. Located in Toronto, 91亚色 is the third largest university in Canada, with a strong community of 53,000 students, 7,000 faculty and administrative staff, and more than 300,000 alumni.

91亚色 U's fully bilingual Glendon Campus is home to Southern Ontario's Centre of Excellence for French Language and Bilingual Postsecondary Education.

Media Contact:聽Anjum Nayyar, 91亚色 Media Relations, 437-242-1547,聽anayyar@yorku.ca

The post How do we see shades of colour? Study shows how our brains calculate the difference appeared first on News@91亚色.