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.

Thanks for the thoughtful reply. I’m highly concerned that there are artifacts baked in. I’ll readily admit that I’m a systems neuroscientist and am skeptical of DWI in general. I appreciate that they included Supp. Fig 13, with a comparison of DWI findings to cellular-level resolution projectome tracing from Allen Institute. Supp Fig 13 does not inspire confidence.

"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.

I think I missed your overall point?

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".

They study macro-scale connectomes.

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.

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

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

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

“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.