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Galili, D. S., Jefferis, G. S., & Costa, M. (2022). Connectomics and the neural basis of behaviour. Current opinion in insect science, 54, 100968. https://doi.org/10.1016/j.cois.2022.100968
When most people hear about how the human mind can be uploaded onto the internet, they tend to think about science fiction works such as Transcendence and Cyberpunk 2077. However, many people don’t know that there is a term for this seemingly futuristic concept: connectomics. Simply put, connectomics is the digital mapping of neuronal connections within the nervous system in order to study specific synapses, or the gap between two neurons, and cell communication; it involves analyzing the billions of neurons and studying the function of either individual neurons or clusters of neurons that form a neural circuit. The curation of a connectome is mainly performed in order to provide insight into how the brain of a specific organism works, allowing them to understand specific neuron and brain region functions.
In order to create a connectome, researchers use technology such as electron microscopy, which uses a beam of charged particles in order to magnify an image, to map out areas of the brain. This type of connectomics is called microscale connectomics, as it revolves around the formation of a connectome at a smaller scale with near-microscopic organisms. In fact, some organisms already have a fully mapped connectome, such as the nematode C. elegans and the fly Drosophila. The other type of connectomics is called macroscale connectomics, which revolves around the mapping of the brain of a larger, more complex organism. For macroscale connectomics, more advanced machines such as fMRI(functional magnetic resonance imaging) and dMRI(diffusion magnetic resonance imaging) have to be used in order to view the brain’s structure. The fMRI machine allows for the display of the function of various sections of the brain while the dMRI machine views the entire brain as a whole. Thus, when these two machines work in conjunction with one another, the creation of a connectome becomes simpler.
Despite the ease provided by the fMRI and dMRI systems, there are immense
challenges that must be faced. For example, in order to ensure that the neuron’s activity and behavior are accurate, there needs to be an excessive amount of proofreading so that the neuron is properly mapped. If there are errors in the neuron’s data then other neurons that are related to the one being analyzed may also be rendered incorrect. Another challenge is neuron identification. Because every person has a different brain with a multitude of variations, it is difficult to identify and correctly group neurons by their function and capacity. Sex, age, and even familial patterns often lead to changes in the human brain. This article compared primary sources on how these factors may affect the mapped connectome.
Using the Drosophila fly model, one group of researchers compared the effect of gender on the connectome. They found a plethora of variations between both genders; while females have neurons more focused on egg-laying and parental aggression, males are more focused on their courtship song and nest identification. They also found that female flies had a more convoluted connectome compared to male flies, attributing this difference to the fact that the females have the ability to switch their neurons from a state of egg-laying to virgin receptivity. Another group discovered that the “smell” neurons within the female flies have specific responses entailed for either male or female flies, with the response for the male flies promoting a higher sense of smell and taste while creating a speed-sensitive sensor for how close the male is.
Works Cited:
Yokoyama, C., Autio, J. A., Ikeda, T., Sallet, J., Mars, R. B., Van Essen, D. C., Glasser, M. F., Sadato, N., & Hayashi, T. (2021). Comparative connectomics of the primate social brain. NeuroImage, 245, 118693. https://doi.org/10.1016/j.neuroimage.2021.118693
US Department of Veterans Affairs. (2010). Retrieved from https://www.va.gov/DIAGNOSTICEM/What_Is_Electron_Microscopy_and_How_Does_It_Work.asp
Baptist Health. (2018). Retrieved from https://www.baptisthealth.com/blog/baptist-health/mri-vs-fmri-what-are-the-differences
Z. Zheng et al. A complete electron microscopy volume of the brain of an adult Drosophila melanogaster. Cell. Vol. 74, July 26, 2018. doi:10.1016/j.cell.2018.06.019.
Cook, S.J., Jarrell, T.A., Brittin, C.A. et al. Whole-animal connectomes of both Caenorhabditis elegans sexes. Nature 571, 63–71 (2019). https://doi.org/10.1038/s41586-019-1352-7
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