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> It turned out that either visual stimulus—the grating or moving dots—resulted in the same patterns of neural activity in the visual cortex and parietal cortex

> It turned out that either visual stimulus—the grating or moving dots—resulted in the same patterns of neural activity in the visual cortex and parietal cortex. The parietal cortex is a part of the brain used in memory processing and storage. > These two distinct visual memories carrying the same relevant information seemed to have been recoded into a shared abstract memory format. As a result, the pattern of brain activity trained to recall motion direction was indistinguishable from that trained to recall the grating orientation. Isn't the alternative explanation that our tooling for inspecting the brain at work abstracts too much detail away for us to be able to tell the difference?

323 5y ago
Indeed, it's like saying "the CPU used 16 Wh of energy, executed 1 billion MOV instructions and 2 billion ADD instructions for both these two tasks, thus the algorithm it ran must be identical".
akyu 5y ago
That's possible. But I think the reason why this is interesting is because you are seeing the same kind of representation in the brain for two seemingly different phenomenon, motion and orientation. It's intuitive to see how you could represent motion by an orientation (we do this with vectors in math), but its interesting to actually see it happen.
theptip 5y ago
Right, it's quite obvious that the memory is not being stored bit-for-bit in exactly the same way because if you ask the person what they saw after the experiment, they will be able to recall the difference of "lines" or "dots". But the paper is explicitly looking at the representation in working memory; so two obvious possibilities are, one that the "orientation" and "dotness vs. lineness" attributes are being decoupled and stored separately in working memory (different "registers" if you will). Or the "dotness / lineness" is getting stored somewhere else (not working memory, some other memory system) because it's not "behaviorally relevant" (i.e. relevant to the task that the participant is attending to while creating the working memory). I'd guess at the first because my impression was that essentially everything that makes it into episodic memory starts in working memory, but I'm not a neuroscientist. I think the OP is getting way ahead of itself with "The findings suggest that participants weren’t actually remembering the grating or a complex cloud of moving dots at all.". The paper is making a much more modest claim that "direction" is recorded in the same underlying way, specifically during a task where you're being asked to recall direction. It's completely possible that this intermediate/common representation would not be generated if you're just looking at the pattern and not performing a task related to direction. I couldn't find the full paper on SciHub, just the abstract linked in the OP: https://pubmed.ncbi.nlm.nih.gov/35395195/ https://pubmed.ncbi.nlm.nih.gov/35395195/. I'd hope the full paper talks about all this in more detail.
dangom 5y ago
Exactly. Our tooling doesn't even allow us to make clear inferences about neuronal activity yet - all we can image with fMRI as of today is heamodynamics. The work proposes that because responses to difference visual stimuli show the same haemodynamic spatiotemporal response in memory areas, the actual memories must share a common representation. This is debatable since we know that localized spatiotemporal responses reflect the variability in the vascular tree and blood flow and volume, regardless of the experiment at hand [see 1 for a discussion]. To dare to claim that effects could be neuronal one needs to run a bunch of extra control experiments (vascular reactivity mapping / breathhold hypercapnic challenges, resting-state imaging as a control dataset), none of which were conducted in the proposed work. This is known to MR physicists, but hasn't clicked in yet within departments of cognitive neuroscience. [1] https://www.frontiersin.org/articles/10.3389/fnins.2020.596084/full https://www.frontiersin.org/articles/10.3389/fnins.2020.5960...

323 5y ago

Indeed, it's like saying "the CPU used 16 Wh of energy, executed 1 billion MOV instructions and 2 billion ADD instructions for both these two tasks, thus the algorithm it ran must be identical".

akyu 5y ago

That's possible. But I think the reason why this is interesting is because you are seeing the same kind of representation in the brain for two seemingly different phenomenon, motion and orientation. It's intuitive to see how you could represent motion by an orientation (we do this with vectors in math), but its interesting to actually see it happen.

theptip 5y ago

Right, it's quite obvious that the memory is not being stored bit-for-bit in exactly the same way because if you ask the person what they saw after the experiment, they will be able to recall the difference of "lines" or "dots". But the paper is explicitly looking at the representation in working memory; so two obvious possibilities are, one that the "orientation" and "dotness vs. lineness" attributes are being decoupled and stored separately in working memory (different "registers" if you will). Or the "dotness / lineness" is getting stored somewhere else (not working memory, some other memory system) because it's not "behaviorally relevant" (i.e. relevant to the task that the participant is attending to while creating the working memory). I'd guess at the first because my impression was that essentially everything that makes it into episodic memory starts in working memory, but I'm not a neuroscientist. I think the OP is getting way ahead of itself with "The findings suggest that participants weren’t actually remembering the grating or a complex cloud of moving dots at all.". The paper is making a much more modest claim that "direction" is recorded in the same underlying way, specifically during a task where you're being asked to recall direction. It's completely possible that this intermediate/common representation would not be generated if you're just looking at the pattern and not performing a task related to direction. I couldn't find the full paper on SciHub, just the abstract linked in the OP: https://pubmed.ncbi.nlm.nih.gov/35395195/ https://pubmed.ncbi.nlm.nih.gov/35395195/. I'd hope the full paper talks about all this in more detail.

dangom 5y ago

Exactly. Our tooling doesn't even allow us to make clear inferences about neuronal activity yet - all we can image with fMRI as of today is heamodynamics. The work proposes that because responses to difference visual stimuli show the same haemodynamic spatiotemporal response in memory areas, the actual memories must share a common representation. This is debatable since we know that localized spatiotemporal responses reflect the variability in the vascular tree and blood flow and volume, regardless of the experiment at hand [see 1 for a discussion]. To dare to claim that effects could be neuronal one needs to run a bunch of extra control experiments (vascular reactivity mapping / breathhold hypercapnic challenges, resting-state imaging as a control dataset), none of which were conducted in the proposed work. This is known to MR physicists, but hasn't clicked in yet within departments of cognitive neuroscience. [1] https://www.frontiersin.org/articles/10.3389/fnins.2020.596084/full https://www.frontiersin.org/articles/10.3389/fnins.2020.5960...