"A petavoxel fragment of human cerebral cortex reconstructed at nanoscale resolution" by Shapson-Coe et al. 2024 (Lichtman lab).
The reconstruction at its current state is already useful and very interesting. Here is to hoping the authors will put in more time and resources to further polish it.
A remarkable finding from Shapson-Coe et al. 2024 paper on human brain #connectomics: the presence of canalized connections in the human brain cortex. Canalized in the Kauffman boolean networks sense [1], which here means: among the many synaptic inputs that any one neuron integrates, some are far stronger (by number of synapses) than the rest.
[1] Canalisation as a term was introduced by Waddington in 1942 in the context of genetics to mean "some phenotypic traits are very robust to small perturbations" https://en.wikipedia.org/wiki/Canalisation_(genetics)
By insisting that every brain-behavior association study include hundreds or even thousands of participants, we risk stifling innovation. Smaller studies are essential to test new scanning paradigms.
Mutatis mutandis, if we had to start off with "hundreds" of connectomes to e.g., measure natural variability in synaptic connectivity among identified neurons, we would have never mapped the first one.
Pilot studies are necessary. Issues arise when, because of the pressure to get grants and splashy papers, one claims too much from that initial study, forgetting about the 'pilot' part.
Incidentally, now, I've put in a grant to request funds for mapping multiple connectomes of the same animal to precisely measure the natural variability. Whether reviewers will dismiss it as "unnecessary" and "uninteresting", now that the first connectome was mapped and published, or as "essential", remains to be seen. I wouldn't have submitted the grant in the first place if I didn't think it was essential.
"In today’s AI research, any project lasting longer than 6 months is considered slow, if not outdated and overrun by history. RoboEM, with a concept and an approach that seem quite plausible, still took 5 years from idea to the fully evaluated tool reported here. This was only possible with the patient support of the Max Planck Society, which encourages long-term projects, and the tenacity of the first author. Details made all the difference. And, as often, dead ends had to be avoided efficiently. We had to abandon, for example, the idea of using steering variability to indicate branch points — a nice analogy to road intersections in car steering, but too far-fetched to work well enough in brain tissue data. Sometimes giving up beloved ideas is as important as following through on others. M.H."
"a connectome is often insufficient to constrain the dynamics of networks that perform a specific task, illustrating the difficulty of inferring function from connectivity alone. However, recordings from a small subset of neurons can remove this degeneracy, ... Our theory can also prioritize which neurons to record from to most efficiently infer unmeasured network activity."
How does #NeuralWiring adapt to different brain sizes? @mgpuxeddu@spornslab use #connectomics of 201 mammals with >10,000x range in brain size to show that spatial embedding constrains larger brains, giving more compact & well defined modules #PLOSBiologyhttps://plos.io/48chjDX
"Recurrent connections enable point attractor dynamics and dimensionality reduction in a connectome-constrained model of the insect learning center", by Joyce et al. 2024
An exploration with computational modeling of feedback inhibition and recurrent excitation – using the #Drosophila olfactory system and learning and memory centre (the mushroom body), as mapped, as an experimental subject.
Our new EU PhD Network #ZooCell is hiring! We have 12 PhD positions in Germany, France, UK, Italy and Sweden.
The broad topic is evolution of sensory cell types in animal diversity: multidisciplinary training in 3D cellular reconstruction (volume EM), multimodal data analysis and science outreach.
Our work made it into the "7 medical breakthroughs that gave us hope in 2023" of #NatGeo – proud! They even chose our image of the #Drosophila larval brain neurons for the header:
The brain of this fairy fly, Megaphragma, is being mapped as we speak. Was imaged by Harald Hess group at HHMI Janelia, then Polilov and Chklovskii groups took it up and have reached out to various groups to collaborate in mapping its connectome.
Turn up the imaging rate of your scanning electron microscope by only imaging at high resolution the areas of the image necessary to resolve ambiguities in the low-res image. Motivated by the need for high-throughput but inexpensive imaging for #connectomics.
Jorge Solís y yo mismo charlamos sobre cómo desarrollar la tecnología necesaria para el campo de la conectómica – el mapeo del cableado neuronal del cerebro y el sistema nervioso entero –, desde abejas y lagartijas a murciélagos y musarañas, como puente para llegar al conectoma del cerebro del ratón.
Our signal propagation atlas of C. elegans is now out in Nature
! We measure the network’s response to optogenetic stimulation of each neuron in the head, one at a time-- over 23,000 neuron pairs. Congrats to Francesco Randi, Anuj Sharma, & Sophie Dvali! https://www.nature.com/articles/s41586-023-06683-4
Why some worms regenerate and others do not
Why are so few species able to regenerate damaged or missing body parts, even though regeneration might seem an obvious survival advantage? Researchers at the Max Planck Institute (MPI) for Multidisciplinary Sciences in Göttingen, Germany, and colleagues have now found a possible explanation in pla... https://nachrichten.idw-online.de/2023/10/20/why-some-worms-regenerate-and-others-do-not
And what a nice photo. Could only have been done by Miquel Vila-Farré – thanks for acknowledging so in the caption. Miquel, my colleague during PhD times in Barcelona. Great memories of many adventures in planaria-land.
I still keep in the back of my mind Pentacoelum hispaniensis, a tiny planarian that one day I'd like to image with FIBSEM to then map its complete nervous system. Would make a great model for how a brain repairs itself.
If interested to do a postdoc on this, I'm game. Write to me.
Areas of particular interest include developing and applying high-density image acquisition methods (electron, X-ray, light) to determine the structure, connectivity and function of intact nervous systems at synaptic resolution; bringing brain-scale connectomics to additional species (including vertebrates); experimental approaches that leverage connectomes to understand brain function; and computational analyses essential for research across these areas.
"By leveraging time-lapse X-ray imaging and brain proxies, we have developed a 12-step protocol, ODeCO, that effectively infiltrates osmium throughout an entire mouse brain while preserving ultrastructure without any cracks or fragmentation, a necessary prerequisite for constructing the first comprehensive mouse brain connectome."
Includes a destaining step to remove excess osmium from the cytosol, increasing the contrast with the cytoplasmic membrane.
"Compared with the honeybee and the fruit fly, Megaphragma exhibits the following miniaturization-related adaptations: a significant reduction in the number of ommatidia, absence of several cell types, reduced size, and denucleation of neurons. Interestingly, the reduction in lens diameter is less than that expected from the optimization of the optical resolution of the eye. This suggests that light sensitivity is a more important
consideration when lens diameter approaches the wavelength of light. The absence of wide-field (or non-columnar) lamina neurons in Megaphragma could be a consequence of the smaller number of ommatidia, their larger acceptance angle, and the lower resolving power of the eye."
Volume assembled with #FijiSc and #TrakEM2, and its neurons and synapses mapped with #CATMAID. Woohoo!
Likewise I've seen the fMRI field attempting to appropriate the word "connectomics", when all they have to show are temporal correlations of BOLD signal across brain areas, not a single anatomical connection. To the point that some of my colleagues now say "cellular connectomics" to refer to, well, actual #connectomics with synapses.