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This is outrageously misleading. To make a claim about the number of synapses between neurons based on MRI data is completely unwarranted. Voxel size (single vo

by tbenst 6y ago

This is outrageously misleading. To make a claim about the number of synapses between neurons based on MRI data is completely unwarranted. Voxel size (single volumetric pixel) in MRI is approximately 1mm, while synapse size is way less than a micron. You need resolution per pixel on the order of 10s of nanometers to identify synapses. I wouldn’t be surprised if a dead salmon also has “equal” connectivity: https://www.wired.com/2009/09/fmrisalmon/ https://www.wired.com/2009/09/fmrisalmon/

gspr 6y ago
Cool your outrage: https://en.wikipedia.org/wiki/Connectome#At_multiple_scales https://en.wikipedia.org/wiki/Connectome#At_multiple_scales
- deleted 6y ago
  [deleted]
- tbenst 6y ago
  “In other words, information travels from one location to another through the same number of synapses.” —-Yaniv Assaf This statement is outrageous, and an example of how some scientists gain the ire of their colleagues by exaggerating their findings and misleading the press.
leemailll 6y ago
And when you put the brain size into consideration, the results for some mammals might not too far a way from a fuzzy mosaic while human’s like a 10 k pixels image
nabla9 6y ago
They study macro-scale connectomes.
- mmastrac 6y ago
  Would it be fair to say that the conclusions were that "large scale processing blocks have similar connection complexity across mammals, regardless of brain size?" -- obviously including that the complexity and/or function of the regions may be wildly different.
  - tbenst 6y ago
    Yes, their statements should be about “large scale processing blocks,“ to make claims to the public about the number of synapses between neurons being conserved is really unfortunate and cannot be assessed in their data
deleted 6y ago
[deleted]
egocodedinsol 6y ago
Surely there's something to learn here though. I haven't read the original paper but a quantity that's preserved across brain scales is either an artifact or a neat insight. Your criticism reads like someone accusing economists of being outrageously misleading when they don't sample individual households but measure macro indicators. It's like saying Ramon y cajal was ridiculous because he couldn't image the neuropil effectively. Or like saying early optogenetics experiments were ridiculous because who knows if you're stimulating a neuron in a realistic manner? And in any case, it's true that synapses are comically small relative to voxel size, but we also have some reasonable information about projection patterns and synapse number from various tracer or rabies studies with which you are no doubt familiar. I haven't read the nature paper the press release is about and I'm not a huge fan of many d/fMRI practices or derived claims. And I've worked with enough mammalian dwi data to be skeptical of specific connection claims. But this strikes me as a rather interesting result even if you can't measure all the synapses at the right resolution: either the tractography method has connectivity conservation artifacts baked in, or there's something interesting going on.
- westurner 6y ago
  "fNIRS Compared with other neuroimaging techniques" https://en.wikipedia.org/wiki/Functional_near-infrared_spectroscopy#fNIRS_Compared_with_other_neuroimaging_techniques https://en.wikipedia.org/wiki/Functional_near-infrared_spect... > When comparing and contrasting these devices it is important to look at the temporal resolution, spatial resolution, and the degree of immobility.
  - egocodedinsol 6y ago
    I think I missed your overall point?
    - westurner 6y ago
      OP suggests that the spatial resolution of existing MRI neuroimaging capabilities is insufficient to observe or so characterize or so generalize about neuronal activity in mammalian species. fNIRS (functional near-infrared spectroscopy) is one alternative neuroimaging capability that we could compare fMRI with according to the criteria for comparison suggested in the cited Wikipedia article: "temporal resolution, spatial resolution, and the degree of immobility".

by tbenst 6y ago

gspr 6y ago

Cool your outrage: https://en.wikipedia.org/wiki/Connectome#At_multiple_scales https://en.wikipedia.org/wiki/Connectome#At_multiple_scales

deleted 6y ago
[deleted]
tbenst 6y ago
“In other words, information travels from one location to another through the same number of synapses.” —-Yaniv Assaf This statement is outrageous, and an example of how some scientists gain the ire of their colleagues by exaggerating their findings and misleading the press.

leemailll 6y ago

And when you put the brain size into consideration, the results for some mammals might not too far a way from a fuzzy mosaic while human’s like a 10 k pixels image

nabla9 6y ago

They study macro-scale connectomes.

mmastrac 6y ago
Would it be fair to say that the conclusions were that "large scale processing blocks have similar connection complexity across mammals, regardless of brain size?" -- obviously including that the complexity and/or function of the regions may be wildly different.
- tbenst 6y ago
  Yes, their statements should be about “large scale processing blocks,“ to make claims to the public about the number of synapses between neurons being conserved is really unfortunate and cannot be assessed in their data

deleted 6y ago

[deleted]

egocodedinsol 6y ago

Surely there's something to learn here though. I haven't read the original paper but a quantity that's preserved across brain scales is either an artifact or a neat insight. Your criticism reads like someone accusing economists of being outrageously misleading when they don't sample individual households but measure macro indicators. It's like saying Ramon y cajal was ridiculous because he couldn't image the neuropil effectively. Or like saying early optogenetics experiments were ridiculous because who knows if you're stimulating a neuron in a realistic manner? And in any case, it's true that synapses are comically small relative to voxel size, but we also have some reasonable information about projection patterns and synapse number from various tracer or rabies studies with which you are no doubt familiar. I haven't read the nature paper the press release is about and I'm not a huge fan of many d/fMRI practices or derived claims. And I've worked with enough mammalian dwi data to be skeptical of specific connection claims. But this strikes me as a rather interesting result even if you can't measure all the synapses at the right resolution: either the tractography method has connectivity conservation artifacts baked in, or there's something interesting going on.

westurner 6y ago
"fNIRS Compared with other neuroimaging techniques" https://en.wikipedia.org/wiki/Functional_near-infrared_spectroscopy#fNIRS_Compared_with_other_neuroimaging_techniques https://en.wikipedia.org/wiki/Functional_near-infrared_spect... > When comparing and contrasting these devices it is important to look at the temporal resolution, spatial resolution, and the degree of immobility.
- egocodedinsol 6y ago
  I think I missed your overall point?
  - westurner 6y ago
    OP suggests that the spatial resolution of existing MRI neuroimaging capabilities is insufficient to observe or so characterize or so generalize about neuronal activity in mammalian species. fNIRS (functional near-infrared spectroscopy) is one alternative neuroimaging capability that we could compare fMRI with according to the criteria for comparison suggested in the cited Wikipedia article: "temporal resolution, spatial resolution, and the degree of immobility".