A handful of neurobiologists, over 2,000 volunteers, and 300,000 classifications. 

This week, Juan Burrone and Guilherme Neves discussed the results of their citizen science project – where over 2000 volunteers played their part in analysing brain slices, helping to map the number and arrangement of synaptic vesicles and mitochondria in neurons.  

This has been a collaboration between the Burrone lab, the Science Scribbler team at the Rosalind Franklin Institute, and the Zooniverse, the world’s largest platform for volunteer-powered research. 

The team at the Burrone lab have been exploring the developing mouse hippocampus – an area involved in learning and memory – during this critical period of circuit wiring. Over the past decade, they have been using high-resolution 3D microscopy to obtain thousands of images – too many to analyse alone! 

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“We were stuck before this project on what's inside these neurons... the information there is mind-bogglingly big, and it's very difficult to extract. If one person was working alone, it would take them many months to be sure about all the connections.” Guilherme Neves 

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Citizen science came to the rescue – with volunteers inspecting, correcting and fine-tuning the best estimates of computational models to map synaptic vesicles and mitochondria.  

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“As somebody who was had never done this [citizen science] before... I was sceptical that it was actually going to work. [But] as soon as we put the first dataset out there, and things moved so fast, and we ran out of data - because everybody had already analysed all of our dataset within a few days - that's when I began to realise that we were on to something, and that this really could be a game changer. And it turned out to be exactly that.” Juan Burrone 

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Thanks to over 1,800 hours of volunteer effort, the team now has a huge volume of annotated data – 10s of 1000s of segmented synaptic boutons. They are intrigued by their findings so far and keen to delve deeper. 

So far, the team have identified differences between the morphology of mitochondria in distal and proximal dendrites, and are excited to explore how these structural differences relate to function. 

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“There's been very few quantitative studies on synaptic vesicles because they're very difficult to segment. [With Synapse Safari] it became possible to start identifying them at scale, which is something that's never been possible before.” Guilherme Neves 

“Like any good experiment, this has thrown open many doors, many new questions... What does it mean for the process of synaptic transmission, for the process of releasing neurotransmitter onto another neuron? And that, I think, is where we should probably take this next: bringing the structure and the function of the synapse together.” Juan Burrone 

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Take a look at the livestream recording or the Zooniverse blog on the project. You can also check out the raw data here.