11 ms·

40 percent of fMRI signals do not correspond to actual brain activity

503 points by geox 11mo ago

bschne 11mo ago
you're telling me the results of this paper were likely bs? --- https://www.sciencedirect.com/science/article/abs/pii/S1053811909712029 https://www.sciencedirect.com/science/article/abs/pii/S10538...
- fishnchips 11mo ago
  Oh man you stole my thunder. I hoped to be the first to bring up the dead salmon.
- parpfish 11mo ago
  The point of the salmon paper is to demonstrate to people “if you do your stats wrong, you’re going to think noise is real” and not “fmri is bs”
  - prefrontal 11mo ago
    As the first author on the salmon paper, yes, that was exactly our point. Researchers were capitalizing on chance in many cases as they failed to do effective corrections to the multiple comparisons problem. We argued with the dead fish that they should.
    - rdgthree 11mo ago
      Nothing to add to this conversation in particular, but just wanted to say - truly amazing paper. Well done!
      - prefrontal 11mo ago
        Many thanks! It was a ton of fun. Hard to beleive that we are coming up on 20 years since the data for the salmon was first collected...
        squeefers 11mo ago
        [flagged]
    - chuckadams 11mo ago
      > We argued with the dead fish that they should. Arguing with a dead fish may be a sign you're working too hard :)
      - prefrontal 11mo ago
        Yeah, it did prove to be a rather one-sided conversation... ;)
        chuckadams 11mo ago
        Did you try tuning it? https://youtu.be/F2y92obnsc0 https://youtu.be/F2y92obnsc0
- kspacewalk2 11mo ago
  Curious what you find to be "bs" about the results of this paper? That statistical corrections are necessary when analysing fMRI scans to prevent spurious "activations" that are only there by chance?
  - koolala 11mo ago
    They were being sarcastic.
- deleted 11mo ago
  [deleted]
mrcrm9494 11mo ago
this headline is a bit misleading on the first read, since it only affects functional (f)MRI, which is controversial since a longer time. a prominent example is the activity that has been detected in a dead salmon
- kspacewalk2 11mo ago
  It's not that fMRI itself is controversial, it's that it is prone to statistical abuse unless you're careful in how you analyse the data. That's what the dead salmon study showed - some voxels will appear "active" purely by statistical chance, so without correction you will get spurious activations.
  - tsimionescu 11mo ago
    This study questions the fMRI method itself, not the statistical analysis (you're right that the dead salmon study was challenging the way statistical analysis is done). Basically, this study claims that the association between the BOLD signal measured by fMRI and actual brain activity is quite weak, and they are even anti-correlated in 40% of cases. There is no statistical analysis that can save you if your interpretation of a signal is wrong (for example, you can't get information about personality from phrenology, regardless of what statistical analysis you try to apply to the data). That's not to say that we need to just trust this study implicitly - I'm just trying to describe how serious of a problem to the field their claim is.
- kgarten 11mo ago
  wondering why you are downvoted. You are right, though it's kind of inferred that the author means fMRI as the title focuses on brain activity only.
- freehorse 11mo ago
  Structural MRI does not record brain activity, because it is, like, structural, not functional. Structural MRI is even more abused, where people find "differences" between 2 groups with ridiculously small sample sizes.
- 11mo ago
belter 11mo ago
Why did TUM let this misleading headline front the news release? Dont we have enough issues with Academia? The result just mean BOLD is an imperfect proxy.
- kspacewalk2 11mo ago
  It is especially unforgiveable that the title of on the news release itself is about "40 percent of MRI signals". What, as in all MRI, not just fMRI? Hopefully an honest typo and not just resulting from ignorance.
darfo 11mo ago
Can the OP change the HN item title so scrollers don't think there is a problem with MRI? Isn't fMRI being questioned?
- dang 11mo ago
  Looks like a mod got to it!
georgeecollins 11mo ago
As someone who used to work at the Cognitive Neurophysiology Lab in the Scripts Institute-- doing some work on functional brain image-- I can confirm this was not news even thirty years ago. I guess this is trying to make some point to lay people?
- Aurornis 11mo ago
  fMRI has been abused by a lot of researchers, doctors, and authors over the years even though experts in the field knew the reality. It’s worth repeating the challenges of interpreting fMRI data to a wider audience.
  - sigmoid10 11mo ago
    The way I understood it is that while individual fMRI studies can be amazing, it is borderline impossible to compare them when made using different people or even different MRI machines. So reproducibility is a big issue, even though the tech itself is extremely promising.
    - Aurornis 11mo ago
      Individual fMRI is not a useful diagnostic tool for general conditions. There have been some clinics trying to push it (or SPECT) as a tool for diagnosing things like ADHD or chronic pain, but there is no scientific basis for this. The operator can basically crank up the noise and get some activity to show up, then tell the patient it’s a sign they have “ring of fire type ADHD” because they set the color pattern to reds and a circular pattern showed up at some point.
    - SubiculumCode 11mo ago
      This isn't really true. The issue is that when you combine data across multiple MRI scanners (sites), you need to account for random effects (e.g. site specific means and variances)...see solutions like COMBAT. Also if they have different equipment versions/manufacturers those scanners can have different SNR profiles. The other issue is that there are many processing with many ways to perform those steps. In general, researchers don't process in multiple ways and choose the way that gives them the result they want or anything nefarious like that, but it does make comparisons difficult since the effects of different preprocessing variations can be significant. To defend against this, many peer reviewers, like myself, request researchers perform the preprocessing multiple ways to assess how robust the results are to those choices. Another way the field has combatted this issue has been software like fMRIprep.
Aurornis 11mo ago
This isn’t entirely news to people in the field doing research, but it’s important information to keep in mind when anyone starts pushing fMRI (or SPECT) scans into popular media discussions about neurology or psychiatry. There have been some high profile influencer doctors pushing brain imaging scans as diagnostic tools for years. Dr. Amen is one of the worst offenders with his clinics that charge thousands of dollars for SPECT scans (not the same as the fMRI in this paper but with similar interpretation issues) on patients. Insurance won’t cover them because there’s no scientific basis for using them in diagnosing or treating ADHD or chronic pain, but his clinics will push them on patients. Seeing an image of their brain with some colors overlayed and having someone confidently read it like tea leaves is highly convincing to people who want answers. Dr. Amen has made the rounds on Dr. Phil and other outlets, as well as amassing millions of followers on social media.
- kspacewalk2 11mo ago
  Dr. Mike, a rare YouTube doctor who is not peddling supplements and wares, and thus seems to be at the forefront of medical critical thinking on the platform, interviewed Dr. Amen recently[0]. I haven't finished the interview yet, but having watched some others, generally the approach is to let the interviewee make their grandiose claims, agree with whatever vague generalities and truisms they use in their rhetoric (yes it's true, doctors don't spend enough time explaining things to patients!), and then lay into them on the actual science and evidence. [0] https://www.youtube.com/watch?v=J-SHgZ1XPXs https://www.youtube.com/watch?v=J-SHgZ1XPXs
  - patmorgan23 11mo ago
    Dr. Mike did an incredible job in that interview. He gave Dr. Amen all the rope to hang himself with his own words. When you're hawking a diagnosis method and you're not interested in building up the foundation of evidence for it by doing a double blinded, randomized controlled study. And that the results of said study would change how your treating patients it's pretty clear who the snake oil salesman is
    - 11mo ago
kspacewalk2 11mo ago
This study is validating a commonplace fMRI measure (change in blood-oxygenation-level-dependent or BOLD signal) by comparing it with a different MRI technique, one that uses a multiparametric quantitative BOLD model, a different model for BOLD derived from two separate MRI scans which measure two different kinds of signal (transverse relaxation rates), and then multiply/divide by a bunch of constants to get at a value. I'm a software engineer in this field, and this is my layman-learns-a-bit-of-shop-talk understanding of it. Both of these techniques involve multiple layers of statistical assumptions, and multiple steps of "analysing" data, which in itself involves implicit assumptions, rules of thumb and other steps that have never sat well with me. A very basic example of this kind of multi-step data massaging is "does this signal look a bit rough? No worries, let's Gaussian-filter it". A lot of my skepticism is due to ignorance, no doubt, and I'd probably be braver in making general claims from the image I get in the end if I was more educated in the actual biophysics of it. But my main point is that it is not at all obvious that you can simply claim "signal B shows that signal A doesn't correspond to actual brain activity", when it is quite arguable whether signal B really does measure the ground truth, or whether it is simply prone to different modelling errors. In the paper itself, the authors say that it is limited by methodology, but because they don't have the device to get an independent measure of brain activation, they use quantitative MRI. They also say it's because of radiation exposure and blah blah, but the real reason is their uni can't afford a PET scanner for them to use. "The gold standard for CBF and CMRO2 measurements is 15O PET; but this technique requires an on-site cyclotron, a sophisticated imaging setup and substantial experience in handling three different radiotracers (CBF, 15O-water; CBV, 15O-CO; OEF, 15O-gas) of short half-lives8,35. Furthermore, this invasive method poses certain risks to participants owing to the exposure to radioactivity and arterial sampling."
- freehorse 11mo ago
  Most studies in non-clinical populations afaik do not use 150 PET though? Afaik this is mostly used for clinical purposes. Could be wrong though.
  - kspacewalk2 11mo ago
    If you have a PET/MR system [0], you can probably do this "gold standard" comparison, and I know that one is used for research studies. I think you can piggy-back off a different study's healthy controls to write a paper like this, if that study already uses PET/MR and if adding an oxygen metabolite scan isn't a big problem. But that's speaking as someone who does not design experiments. [0] https://www.siemens-healthineers.com/en-us/magnetic-resonance-imaging/mr-pet-scanner/biograph-mmr https://www.siemens-healthineers.com/en-us/magnetic-resonanc...
NalNezumi 11mo ago
My previous job was at a startup doing BMI, for research. For the first time I had the chance to work with expensive neural signal measurement tools (mainly EEG for us, but some teams used fMRI). and quickly did I learn how absolute horrible the signal to noise ratio (SNR) was in this field. And how it was almost impossible to reproduce many published and well cited result. It was both exciting and jarring to talk with the neuroscientist, because they ofc knew about this and knew how to read the papers but the one doing more funding/business side ofc didn't really spend much time putting emphasis on that. One of the team presented a accepted paper that basically used Deep Learning (Attention) to predict images that a person was thinking of, from the fMRI signals. When I asked "but DL is proven to be able to find pattern even in random noise, so how can you be sure this is not just overfitting to artefact?" and there wasn't really any answer to that (or rather the publication didn't take that in to account, although that can be experimentally determined). Still, a month later I saw tech explore or some tech news writing an article about it, something like "AI can now read your brain" and the 1984 implications yada yada. So this is indeed something probably most practitioners, masters and PhD, realize relatively early. So now that someone says "you know mindfulness is proven to change your brainwaves?" I always add my story "yes, but the study was done with EEG, so I don't trust the scientific backing of it" (but anecdotally, it helps me)
- deleted 11mo ago
  [deleted]
- D-Machine 11mo ago
  The difference is that EEG can be used usefully in e.g. biofeedback training and the study of sleep phases, so there is in fact enough signal here for it to be broadly useful in some simple cases. It is not clear fMRI has enough signal for anything even as simple as these things though.
  - j45 11mo ago
    I have been told QEEG can offer an additional perspective in neurofeedback, etc as well. fMRI's are being used in TBI/Concussion recovery that are study backed and seem to be delivering results.
pdevr 11mo ago
>which are known to produce predictable fMRI signal changes in distributed brain regions. Wondering how they created that baseline. Was it with fMRI data (which has deviance from actual data, as pointed out)? Or was it through other means?
D-Machine 11mo ago
It's so much worse than this. For task fMRI, the test-retest reliability is so poor it should probably be considered useless or bordering on pseudoscience, except for in some very limited cases like activation of the visual and/or auditory and/or motor cortex with certain kinds of clear stimuli. For resting-state fMRI (rs-fMRI), the reliabilities are a bit better, but also still generally extremely poor [1-3]. There are also two IMO major and devastating theoretical concerns re fMRI that IMO make the whole thing border on nonsense. One is the assumed relation between the BOLD signal and "activation", and two is the extremely horrible temporal resolution of fMRI. It is typically assumed that the BOLD response (increased oxygen uptake) (1) corresponds to greater metabolic activity, and (2) increased metabolic activity corresponds to "activation" of those tissues. This trades dubiously on the meaning of "activation", often assuming "activation = excitatory", when we know in fact much metabolic activity is inhibitory. fMRI cannot distinguish between these things. There are other deeper issues, in that it is not even clear to what extent the BOLD signal is from neurons at all (could be glia), and it is possible the BOLD signal must be interpreted differently in different brain regions, and that the usual analyses looking for a "spike" in BOLD activity are basically nonsense, since BOLD activity isn't even related to this at all, but rather the local field potential, instead. All this is reviewed in [4]. Re: temporal resolution, essentially, if you pay attention to what is going on in your mind, you know that a LOT of thought can happen in just 0.5 seconds (think of when you have a flash of insight that unifies a bunch of ideas). Or think of how quickly processing must be happening in order for us to process a movie or animation sequence where there are up to e.g. 10 cuts / shots within a single second. There is also just biological evidence that neurons take only milliseconds to spike, and that a sequence of spikes (well under 100ms) can convey meaningful information. However, the lowest temporal resolutions (repetition times) in fMRI are only around 0.7 seconds. IMO this means that the ONLY way to analyze fMRI that makes sense is to see it as an emergent phenomenon that may be correlated with certain kinds of long-term activity reflecting cyclical BOLD patterns / low-frequency patterns of the BOLD response. I.e. rs-fMRI is the only fMRI that has ever made much sense a priori. The solution to this is maybe to combine EEG (extremely high temporal resolution, clear use in monitoring realtime brain changes like meditative states and in biofeedback training) with fMRI, as in e.g. [5]. But, it may still well be just the case fMRI remains mostly useless. [1] Elliott, M. L., Knodt, A. R., Ireland, D., Morris, M. L., Poulton, R., Ramrakha, S., Sison, M. L., Moffitt, T. E., Caspi, A., & Hariri, A. R. (2020). What Is the Test-Retest Reliability of Common Task-Functional MRI Measures? New Empirical Evidence and a Meta-Analysis. Psychological Science, 31(7), 792–806. https://doi.org/10.1177/0956797620916786 https://doi.org/10.1177/0956797620916786 [2] Herting, M. M., Gautam, P., Chen, Z., Mezher, A., & Vetter, N. C. (2018). Test-retest reliability of longitudinal task-based fMRI: Implications for developmental studies. Developmental Cognitive Neuroscience, 33, 17–26. https://doi.org/10.1016/j.dcn.2017.07.001 https://doi.org/10.1016/j.dcn.2017.07.001 [3] Termenon, M., Jaillard, A., Delon-Martin, C., & Achard, S. (2016). Reliability of graph analysis of resting state fMRI using test-retest dataset from the Human Connectome Project. NeuroImage, 142, 172–187. https://doi.org/10.1016/j.neuroimage.2016.05.062 https://doi.org/10.1016/j.neuroimage.2016.05.062 [4] Ekstrom, A. (2010). How and when the fMRI BOLD signal relates to underlying neural activity: The danger in dissociation. Brain Research Reviews, 62(2), 233–244. https://doi.org/10.1016/j.brainresrev.2009.12.004 https://doi.org/10.1016/j.brainresrev.2009.12.004, https://scholar.google.ca/scholar?cluster=6420450573860538418&hl=en&as_sdt=0,5&as_rr=1 https://scholar.google.ca/scholar?cluster=642045057386053841... [5] Ahmad, R. F., Malik, A. S., Kamel, N., Reza, F., & Abdullah, J. M. (2016). Simultaneous EEG-fMRI for working memory of the human brain. Australasian Physical & Engineering Sciences in Medicine, 39(2), 363–378. https://doi.org/10.1007/s13246-016-0438-x https://doi.org/10.1007/s13246-016-0438-x
zerof1l 11mo ago
I wonder how much variation there is between a person who does certain mental activity regularly vs a person who rarely does it. If they were to measure a person who performs mental arithmetic on a daily basis, I'd expect his brain activity and oxygen consumption to be lower than those of a person who never does it. How much difference would that make?
- cj 11mo ago
  I did a fMRI study as a volunteer in college. It involved going to the lab and practicing the thing (a puzzle / maze) I would be shown during the actual MRI. I think I went in to “practice” a couple times before showing up and doing it in the machine. IIRC the purpose of practicing was exactly that, to avoid me trying ti learn something during the scan (since that wasn’t the intention of the study). In other words, I think you can control for that variable. (Side note: I absolutely fell asleep during half the scan. Oops! I felt bad, but I guess that’s a risk when you recruit sleep deprived college kids!)
- subroutine 11mo ago
  I worked in an fMRI lab briefly as a grad student. I suspect you'd be correct but perhaps not exactly why you'd expect. Studies using fMRI measure a blood-oxygenation-level-dependent (BOLD) signal in the brain. This is thought to be an indirect measure of neural activity because a local increase in neural firing rate produces a local increase in the need for, and delivery of, oxygenated blood. The question then is, do you expect a person who is really good at mental arithmetic to have less neural firing on arithmetic tasks (e.g., what is 147 x 38) than the average joe. I would hypothesize yes overall to solve each question; however, I'd also hypothesize the momentary max intensity of the expert to peak higher. Think of a bodybuilder vs. a SWE bench-pressing 100 lbs for 50 reps. The bodybuilder has way more muscle to devote to a single rep, and will likely finish the set in 20 seconds, while the SWE is going to take like 30 minutes ;)
deleted 11mo ago
[deleted]
antipaul 11mo ago
Biotech industrial complex fMRI is a cool, expensive tech, like so many others in genetics and other diagnostics. These technologies create good jobs ("doing well by doing good"). But as other comments point out, and practitioners know, their usefulness for patients is more dubious.
yboris 11mo ago
In related news: ironically, Psychedelics disrupt normal link between brain’s neuronal activity and blood flow - thus casting some doubt on findings that under psychedelics more of the brain is connected (since fMRI showed elevated blood flow, suggesting higher brain activity). https://source.washu.edu/2025/12/psychedelics-disrupt-normal-link-between-brains-neuronal-activity-and-blood-flow/ https://source.washu.edu/2025/12/psychedelics-disrupt-normal...
- HocusLocus 11mo ago
  As a caveman pondering "Stoned Ape Theory" during the rise of MRI in the 80s, having done light reading of Huxley, McKenna et. al, the claim that vascular variations were so tied to thought patterns in a purely calm and cognitive activity was fascinating. To see the brain of someone as they went through a deck of cards and paused to look at each... astounding! But frustrating also. My first question always was, was the person's hands busy going through the deck and holding up the cards, focusing on them... or were they merely shown the cards sitting still? It seemed the popsci articles often glossed over that information, and any simple "control for coordinated body movement" played second fiddle to the novelty of it all. Then I worked in a club where I was often surrounded by tripping people. I'd fetch them glasses of water and they would always drink. Do you know you can smell them, they smell like fear? The experience has every sweat gland working overtime. When I learned that I greeted this "tripping people MRIs light up indicating enhanced brain connectivity" with a grain of salt. I would not be the least bit surprised if the sweat gland thing also has the brain's vascular system in overdrive.
  - yboris 11mo ago
    My favorite explanation for why LSD and similar psychedelics generate the visual patterns they do: mathematics of wrapping polar coordinates of the retina to the rectangular coordinates of the visual processing system: https://www.quantamagazine.org/a-math-theory-for-why-people-hallucinate-20180730/ https://www.quantamagazine.org/a-math-theory-for-why-people-...
SubiculumCode 11mo ago
I'll get raked for this, but as someone in the field, I can say with high confidence that the majority of comments in this thread are not from imaging experts, and mostly (mis)informed by popular science articles. I do not have the time to properly respond to each issue I see. The literature is out there in any case.
- DANmode 11mo ago
  Seeing HN take on your speciality or topic can be brutal. Condolences.
  - Loughla 11mo ago
    I hide any thread that deals with education, education funding, or teaching in general for that specific reason. It really saddens me to see that this place is full of so much misinformation and anecdotes made into data (and usually with much more self-confidence than other forums, which is interesting to me). It's why I generally only ask questions, or ask for clarification instead of directly challenging something I think might be wrong now in threads that aren't related to something I have deeeeep personal knowledge of. I know when I'm out of my area, and don't want to add to the ignorance.
    - NemoNobody 11mo ago
      Challenging something with a question about it, is not adding to ignorance - if a statement/study/fact/belief can't hold to up to questions, from actual opposing critics, what's the point of that position existing? Being all "PC" and "nice" about stuff that is what it is, or isn't -- THAT adds to ignorance.
      - Loughla 11mo ago
        I guess maybe I didn't phrase that correctly - I ask challenging questions, but don't state the things I "know" without clarification first. I meant that I don't just pop off with "yeah, but in reality it's x, y, z" because I know that I'm probably ignorant of facts. I'll ask about x, y, or z first.
riazrizvi 11mo ago
The researchers found that “40% of increased fMRI signal correspond to a decrease in neuronal activity”, so it’s even worse than the headline.
rcv 11mo ago
I remember reading a paper back in grad school where the researchers put a dead salmon in the magnet and got statistically significant brain activity readings using whatever the analysis method à la mode was. It felt like a great candidate for the Ig Nobel awards.
- prefrontal 11mo ago
  That was our paper! We showed that you can get false positives (significant brain activity in this case) if fMRI if you don't use the proper statistical corrections. We did win an Ig Nobel for that work in 2012 - it was a ton of fun.
  - dang 11mo ago
    This is one for https://news.ycombinator.com/highlights https://news.ycombinator.com/highlights! (I mention this so more people can know the list exists, and hopefully email us more nominations when they see an unusually great and interesting comment.) p.s. more on the salmon paper in this thread: https://news.ycombinator.com/item?id=46291600 https://news.ycombinator.com/item?id=46291600 https://news.ycombinator.com/item?id=46288560 https://news.ycombinator.com/item?id=46288560 https://news.ycombinator.com/item?id=46288557 https://news.ycombinator.com/item?id=46288557
    - jldugger 11mo ago
      Interesting -- I just use https://news.ycombinator.com/best?h=168 https://news.ycombinator.com/best?h=168 for a weekly roundup, but that only tracks posts. Might need to supplement it with highlights or similar. Reviewing the HN docs, https://news.ycombinator.com/bestcomments?h=168 https://news.ycombinator.com/bestcomments?h=168 might also be a good summary link.
isacdaavid 11mo ago
If you actually read their paper, you will find that it's only the sign of the correlation that is being questioned. The field has generally been aware of this interpretational gap, and that's why two-sided hypothesis tests are important. Cellular neuroscience and electrophysiology are only starting to face the challenges that fMRI faced 2 decades ago. To me this is like shitting on cars in 1925 because they kill people every now and then. Cars didn't go away, and nor will fMRI, until someone finds a better way to measure living people's brains. TUM's press is being sloppy, from conflating fMRI with MRI to presuming this is revolutionary, and ignoring earlier empirical work against this narrative (Windkessel's, Logothetis beta/gamma coupling, etc.)
Trickery5837 11mo ago
let me write the correct title for you: "new evidence that fMRI data should be processed and interpreted only in the presence of an adult"
eykanal 11mo ago
Now seems like a good time to remind folks of the Stanford dead fish fMRI study: https://law.stanford.edu/2009/09/18/what-a-dead-salmon-reminds-us-about-fmri-analysis/ https://law.stanford.edu/2009/09/18/what-a-dead-salmon-remin... fMRI has always had folks highlighting how shaky the science is. It's not the strongest of experimental techniques.
- levocardia 11mo ago
  fMRI methods and statistics have advanced quite a lot since the dead fish days, that critique does not really hold up today.
  - prefrontal 11mo ago
    While I would agree that the prevalence of the problem has been minimized in fMRI during the last 15 years, I disagree that our critique does not hold up. The root of our concern was that proper statistical correction(s) need to be completed in order for research results to be interpretable. I am totally biased, but I think that remains worthwhile.
- zahlman 11mo ago
  I immediately thought of it too. Didn't realize it was that long ago.
- dang 11mo ago
  Discussed here. others? Risk of false positives in fMRI of post-mortem Atlantic salmon (2010) [pdf] - https://news.ycombinator.com/item?id=15598429 https://news.ycombinator.com/item?id=15598429 - Nov 2017 (41 comments) Scanning dead salmon in fMRI machine (2009) - https://news.ycombinator.com/item?id=831454 https://news.ycombinator.com/item?id=831454 - Sept 2009 (1 comment)
- cafebeen 11mo ago
  This study was really highlighting a statistical issue which would occur with any imaging technique with noise (which is unavoidable). If you measure enough things, you'll inevitably find some false positives. The solution is to use procedures such as Bonferroni and FDR to correct for the multiple tests, now a standard part of such imaging experiments. It's a valid critique, but it's worth highlighting that it's not specific to fMRI or evidence of shaky science unless you skip those steps (other separate factors may indicate shakiness though).
Olshansky 11mo ago
I didn't get my name on this, but contributed to it as an undergrad: https://ieeexplore.ieee.org/abstract/document/6903679 https://ieeexplore.ieee.org/abstract/document/6903679 We sped up fMRI analysis using distributed computing (MapReduce) and GPUs back in 2014. Funny how nothing has changes.
j45 11mo ago
What's surprising is the desire to have a silver bullet, or not solution. What's still amazing is fMRI can provide more visual context of what's happening in the brain, in what region, and activities that can help that improve. There are other complementary technologies like QEEG and SPECT that can also shed a light as well. It does seem the case that fMRI cann be more of a snapshot photo, and technologies like SPECT can provide more of a regional time lapse of activity.
voxleone 11mo ago
It is the microbiome, stupid. [just kidding]
subroutine 11mo ago
I was a grad student at UCSD when Ed Vul published Voodoo Correlations in Social Neuroscience [1], which stoked a severe backlash from the fMRI syndicate resulting in a title change to Puzzlingly High Correlations in fMRI Studies of Emotion, Personality, and Social Cognition [2]. There is a lot of interesting commentary around this article (e.g., “Voodoo” Science in Neuroimaging: How a Controversy Transformed into a Crisis [3]). To me it was fascinating to watch Vul (an incredibly rare talent, perhaps a genius), take on an entire field during his 1st year as assistant professor. 1. http://prefrontal.org/blog/2009/01/voodoo-correlations-in-social-neuroscience/ http://prefrontal.org/blog/2009/01/voodoo-correlations-in-so... 2. https://journals.sagepub.com/doi/10.1111/j.1745-6924.2009.01125.x https://journals.sagepub.com/doi/10.1111/j.1745-6924.2009.01... 3. https://www.mdpi.com/2076-0760/12/1/15 https://www.mdpi.com/2076-0760/12/1/15
instagraham 11mo ago
I might be oversimplifying, but isn't a lot of our neurological understanding about ADHD based on "fMRI shows decreased activity in the frontal cortex"? Or for that matter, our neurological understanding of a lot of mental health conditions. I know the actual diagnosis is several times more layered than this attempt at an explanation, but I always felt that trying to explain the brain by peering at it from outwards is like trying to debug code by looking at a motherboard through a bad microscope.
- supersour 11mo ago
  Yes this is true, but we actually have a lot more data to back this on than exclusively fMRI analysis - for example the ADHD medication guanfacine works only because the alpha 2 receptors happen to be wired differently in the prefrontal cortex than it is in other areas of the brain (a2 is inhibitory for most brain regions, but in the PFC they're positioned to amplify connections between neurons) , so by stimulating alpha 2 we allow for a more “top down” control from the prefrontal cortex than we do without, which improves executive function. So that is one extremely robust way to understand neurological conditions like ADHD or Parkinson’s
  - instagraham 11mo ago
    With such medications, besides behavioural changes, how are they able to measure outcomes without fMRIs? Like knowing whether neuron connections are amplified or not?
    - D-Machine 11mo ago
      They don't, this is speculative (i.e. a theory) and almost certainly untrue (or a gross over-simplification), much like the early and now disproven serotonin theories of depression.
- D-Machine 11mo ago
  I do not think there is much neurological understanding about ADHD at all from current fMRI research, there are far too many quality and reliability issues here, not just on the fMRI end or limited amount of data overall, but in the measurement and diagnosis of ADHD itself (i.e. ADHD subtypes, and of course ADHD is a complicated diagnosis with many components manifesting to different degrees in different individuals, which makes it very hard to cleanly link to messy fMRI signals). Or, as I have commented elsewhere here, the idea that statements like "fMRI shows decreased activity" are ever valid is just fundamentally suspect (lower BOLD response could mean less inhibition or less excitation, and this is a rather crucial difference that fMRI simply can't distinguish). EDIT: Or to be more precise: it may well be that fMRI research suggests less metabolic activity in certain regions, but this could mean the region is actually firing more than normal, less than normal, is more efficient than normal, etc., and interpreting anything about what is functioning differently in ADHD, given this uncertainty, is what is going to be suspect. Your analogy is largely correct IMO.
NedF 11mo ago
[dead]
quasarj 11mo ago
Uh-oh
stainablesteel 11mo ago
> Many fMRI studies on psychiatric or neurological diseases – from depression to Alzheimer’s – interpret changes in blood flow as a reliable signal of neuronal under- or over-activation. Given the limited validity of such measurements, this must now be reassessed idk about that, the brain is complicated, blood flow itself may as well be a factor to interpret
sharts 11mo ago
So all the studies citing fmri data are now wrong probably? yikes
physPop 11mo ago
Unfortunately, for experts in the field, this is a "we know" article that probably shouldn't have been published, and belongs more in a textbook...
- D-Machine 11mo ago
  Yes this is ancient news for experts, but, IMO, most fMRI research outside of methodological research is quite practically useless at the moment because of deep measurement issues like these. So if awareness of this increases the skepticism of papers claiming to have learned things about the brain/mind from fMRI, then I'd say it is a net plus.
bookofjoe 11mo ago
>BOLD signal changes can oppose oxygen metabolism across the human cortex (no paywall) https://www.nature.com/articles/s41593-025-02132-9 https://www.nature.com/articles/s41593-025-02132-9

503 points by geox 11mo ago

bschne 11mo ago

you're telling me the results of this paper were likely bs? --- https://www.sciencedirect.com/science/article/abs/pii/S1053811909712029 https://www.sciencedirect.com/science/article/abs/pii/S10538...

fishnchips 11mo ago
Oh man you stole my thunder. I hoped to be the first to bring up the dead salmon.
parpfish 11mo ago
The point of the salmon paper is to demonstrate to people “if you do your stats wrong, you’re going to think noise is real” and not “fmri is bs”
- prefrontal 11mo ago
  As the first author on the salmon paper, yes, that was exactly our point. Researchers were capitalizing on chance in many cases as they failed to do effective corrections to the multiple comparisons problem. We argued with the dead fish that they should.
  - rdgthree 11mo ago
    Nothing to add to this conversation in particular, but just wanted to say - truly amazing paper. Well done!
    - prefrontal 11mo ago
      Many thanks! It was a ton of fun. Hard to beleive that we are coming up on 20 years since the data for the salmon was first collected...
      - squeefers 11mo ago
        [flagged]
  - chuckadams 11mo ago
    > We argued with the dead fish that they should. Arguing with a dead fish may be a sign you're working too hard :)
    - prefrontal 11mo ago
      Yeah, it did prove to be a rather one-sided conversation... ;)
      - chuckadams 11mo ago
        Did you try tuning it? https://youtu.be/F2y92obnsc0 https://youtu.be/F2y92obnsc0
kspacewalk2 11mo ago
Curious what you find to be "bs" about the results of this paper? That statistical corrections are necessary when analysing fMRI scans to prevent spurious "activations" that are only there by chance?
- koolala 11mo ago
  They were being sarcastic.
deleted 11mo ago
[deleted]

mrcrm9494 11mo ago

this headline is a bit misleading on the first read, since it only affects functional (f)MRI, which is controversial since a longer time. a prominent example is the activity that has been detected in a dead salmon

kspacewalk2 11mo ago
It's not that fMRI itself is controversial, it's that it is prone to statistical abuse unless you're careful in how you analyse the data. That's what the dead salmon study showed - some voxels will appear "active" purely by statistical chance, so without correction you will get spurious activations.
- tsimionescu 11mo ago
  This study questions the fMRI method itself, not the statistical analysis (you're right that the dead salmon study was challenging the way statistical analysis is done). Basically, this study claims that the association between the BOLD signal measured by fMRI and actual brain activity is quite weak, and they are even anti-correlated in 40% of cases. There is no statistical analysis that can save you if your interpretation of a signal is wrong (for example, you can't get information about personality from phrenology, regardless of what statistical analysis you try to apply to the data). That's not to say that we need to just trust this study implicitly - I'm just trying to describe how serious of a problem to the field their claim is.
kgarten 11mo ago
wondering why you are downvoted. You are right, though it's kind of inferred that the author means fMRI as the title focuses on brain activity only.
freehorse 11mo ago
Structural MRI does not record brain activity, because it is, like, structural, not functional. Structural MRI is even more abused, where people find "differences" between 2 groups with ridiculously small sample sizes.
11mo ago

belter 11mo ago

Why did TUM let this misleading headline front the news release? Dont we have enough issues with Academia? The result just mean BOLD is an imperfect proxy.

kspacewalk2 11mo ago
It is especially unforgiveable that the title of on the news release itself is about "40 percent of MRI signals". What, as in all MRI, not just fMRI? Hopefully an honest typo and not just resulting from ignorance.

darfo 11mo ago

Can the OP change the HN item title so scrollers don't think there is a problem with MRI? Isn't fMRI being questioned?

dang 11mo ago
Looks like a mod got to it!

georgeecollins 11mo ago

As someone who used to work at the Cognitive Neurophysiology Lab in the Scripts Institute-- doing some work on functional brain image-- I can confirm this was not news even thirty years ago. I guess this is trying to make some point to lay people?

Aurornis 11mo ago
fMRI has been abused by a lot of researchers, doctors, and authors over the years even though experts in the field knew the reality. It’s worth repeating the challenges of interpreting fMRI data to a wider audience.
- sigmoid10 11mo ago
  The way I understood it is that while individual fMRI studies can be amazing, it is borderline impossible to compare them when made using different people or even different MRI machines. So reproducibility is a big issue, even though the tech itself is extremely promising.
  - Aurornis 11mo ago
    Individual fMRI is not a useful diagnostic tool for general conditions. There have been some clinics trying to push it (or SPECT) as a tool for diagnosing things like ADHD or chronic pain, but there is no scientific basis for this. The operator can basically crank up the noise and get some activity to show up, then tell the patient it’s a sign they have “ring of fire type ADHD” because they set the color pattern to reds and a circular pattern showed up at some point.
  - SubiculumCode 11mo ago
    This isn't really true. The issue is that when you combine data across multiple MRI scanners (sites), you need to account for random effects (e.g. site specific means and variances)...see solutions like COMBAT. Also if they have different equipment versions/manufacturers those scanners can have different SNR profiles. The other issue is that there are many processing with many ways to perform those steps. In general, researchers don't process in multiple ways and choose the way that gives them the result they want or anything nefarious like that, but it does make comparisons difficult since the effects of different preprocessing variations can be significant. To defend against this, many peer reviewers, like myself, request researchers perform the preprocessing multiple ways to assess how robust the results are to those choices. Another way the field has combatted this issue has been software like fMRIprep.

Aurornis 11mo ago

This isn’t entirely news to people in the field doing research, but it’s important information to keep in mind when anyone starts pushing fMRI (or SPECT) scans into popular media discussions about neurology or psychiatry. There have been some high profile influencer doctors pushing brain imaging scans as diagnostic tools for years. Dr. Amen is one of the worst offenders with his clinics that charge thousands of dollars for SPECT scans (not the same as the fMRI in this paper but with similar interpretation issues) on patients. Insurance won’t cover them because there’s no scientific basis for using them in diagnosing or treating ADHD or chronic pain, but his clinics will push them on patients. Seeing an image of their brain with some colors overlayed and having someone confidently read it like tea leaves is highly convincing to people who want answers. Dr. Amen has made the rounds on Dr. Phil and other outlets, as well as amassing millions of followers on social media.

kspacewalk2 11mo ago
Dr. Mike, a rare YouTube doctor who is not peddling supplements and wares, and thus seems to be at the forefront of medical critical thinking on the platform, interviewed Dr. Amen recently[0]. I haven't finished the interview yet, but having watched some others, generally the approach is to let the interviewee make their grandiose claims, agree with whatever vague generalities and truisms they use in their rhetoric (yes it's true, doctors don't spend enough time explaining things to patients!), and then lay into them on the actual science and evidence. [0] https://www.youtube.com/watch?v=J-SHgZ1XPXs https://www.youtube.com/watch?v=J-SHgZ1XPXs
- patmorgan23 11mo ago
  Dr. Mike did an incredible job in that interview. He gave Dr. Amen all the rope to hang himself with his own words. When you're hawking a diagnosis method and you're not interested in building up the foundation of evidence for it by doing a double blinded, randomized controlled study. And that the results of said study would change how your treating patients it's pretty clear who the snake oil salesman is
  - 11mo ago

kspacewalk2 11mo ago

This study is validating a commonplace fMRI measure (change in blood-oxygenation-level-dependent or BOLD signal) by comparing it with a different MRI technique, one that uses a multiparametric quantitative BOLD model, a different model for BOLD derived from two separate MRI scans which measure two different kinds of signal (transverse relaxation rates), and then multiply/divide by a bunch of constants to get at a value. I'm a software engineer in this field, and this is my layman-learns-a-bit-of-shop-talk understanding of it. Both of these techniques involve multiple layers of statistical assumptions, and multiple steps of "analysing" data, which in itself involves implicit assumptions, rules of thumb and other steps that have never sat well with me. A very basic example of this kind of multi-step data massaging is "does this signal look a bit rough? No worries, let's Gaussian-filter it". A lot of my skepticism is due to ignorance, no doubt, and I'd probably be braver in making general claims from the image I get in the end if I was more educated in the actual biophysics of it. But my main point is that it is not at all obvious that you can simply claim "signal B shows that signal A doesn't correspond to actual brain activity", when it is quite arguable whether signal B really does measure the ground truth, or whether it is simply prone to different modelling errors. In the paper itself, the authors say that it is limited by methodology, but because they don't have the device to get an independent measure of brain activation, they use quantitative MRI. They also say it's because of radiation exposure and blah blah, but the real reason is their uni can't afford a PET scanner for them to use. "The gold standard for CBF and CMRO2 measurements is 15O PET; but this technique requires an on-site cyclotron, a sophisticated imaging setup and substantial experience in handling three different radiotracers (CBF, 15O-water; CBV, 15O-CO; OEF, 15O-gas) of short half-lives8,35. Furthermore, this invasive method poses certain risks to participants owing to the exposure to radioactivity and arterial sampling."

freehorse 11mo ago
Most studies in non-clinical populations afaik do not use 150 PET though? Afaik this is mostly used for clinical purposes. Could be wrong though.
- kspacewalk2 11mo ago
  If you have a PET/MR system [0], you can probably do this "gold standard" comparison, and I know that one is used for research studies. I think you can piggy-back off a different study's healthy controls to write a paper like this, if that study already uses PET/MR and if adding an oxygen metabolite scan isn't a big problem. But that's speaking as someone who does not design experiments. [0] https://www.siemens-healthineers.com/en-us/magnetic-resonance-imaging/mr-pet-scanner/biograph-mmr https://www.siemens-healthineers.com/en-us/magnetic-resonanc...

NalNezumi 11mo ago

My previous job was at a startup doing BMI, for research. For the first time I had the chance to work with expensive neural signal measurement tools (mainly EEG for us, but some teams used fMRI). and quickly did I learn how absolute horrible the signal to noise ratio (SNR) was in this field. And how it was almost impossible to reproduce many published and well cited result. It was both exciting and jarring to talk with the neuroscientist, because they ofc knew about this and knew how to read the papers but the one doing more funding/business side ofc didn't really spend much time putting emphasis on that. One of the team presented a accepted paper that basically used Deep Learning (Attention) to predict images that a person was thinking of, from the fMRI signals. When I asked "but DL is proven to be able to find pattern even in random noise, so how can you be sure this is not just overfitting to artefact?" and there wasn't really any answer to that (or rather the publication didn't take that in to account, although that can be experimentally determined). Still, a month later I saw tech explore or some tech news writing an article about it, something like "AI can now read your brain" and the 1984 implications yada yada. So this is indeed something probably most practitioners, masters and PhD, realize relatively early. So now that someone says "you know mindfulness is proven to change your brainwaves?" I always add my story "yes, but the study was done with EEG, so I don't trust the scientific backing of it" (but anecdotally, it helps me)

deleted 11mo ago
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D-Machine 11mo ago
The difference is that EEG can be used usefully in e.g. biofeedback training and the study of sleep phases, so there is in fact enough signal here for it to be broadly useful in some simple cases. It is not clear fMRI has enough signal for anything even as simple as these things though.
- j45 11mo ago
  I have been told QEEG can offer an additional perspective in neurofeedback, etc as well. fMRI's are being used in TBI/Concussion recovery that are study backed and seem to be delivering results.

pdevr 11mo ago

>which are known to produce predictable fMRI signal changes in distributed brain regions. Wondering how they created that baseline. Was it with fMRI data (which has deviance from actual data, as pointed out)? Or was it through other means?

D-Machine 11mo ago

It's so much worse than this. For task fMRI, the test-retest reliability is so poor it should probably be considered useless or bordering on pseudoscience, except for in some very limited cases like activation of the visual and/or auditory and/or motor cortex with certain kinds of clear stimuli. For resting-state fMRI (rs-fMRI), the reliabilities are a bit better, but also still generally extremely poor [1-3]. There are also two IMO major and devastating theoretical concerns re fMRI that IMO make the whole thing border on nonsense. One is the assumed relation between the BOLD signal and "activation", and two is the extremely horrible temporal resolution of fMRI. It is typically assumed that the BOLD response (increased oxygen uptake) (1) corresponds to greater metabolic activity, and (2) increased metabolic activity corresponds to "activation" of those tissues. This trades dubiously on the meaning of "activation", often assuming "activation = excitatory", when we know in fact much metabolic activity is inhibitory. fMRI cannot distinguish between these things. There are other deeper issues, in that it is not even clear to what extent the BOLD signal is from neurons at all (could be glia), and it is possible the BOLD signal must be interpreted differently in different brain regions, and that the usual analyses looking for a "spike" in BOLD activity are basically nonsense, since BOLD activity isn't even related to this at all, but rather the local field potential, instead. All this is reviewed in [4]. Re: temporal resolution, essentially, if you pay attention to what is going on in your mind, you know that a LOT of thought can happen in just 0.5 seconds (think of when you have a flash of insight that unifies a bunch of ideas). Or think of how quickly processing must be happening in order for us to process a movie or animation sequence where there are up to e.g. 10 cuts / shots within a single second. There is also just biological evidence that neurons take only milliseconds to spike, and that a sequence of spikes (well under 100ms) can convey meaningful information. However, the lowest temporal resolutions (repetition times) in fMRI are only around 0.7 seconds. IMO this means that the ONLY way to analyze fMRI that makes sense is to see it as an emergent phenomenon that may be correlated with certain kinds of long-term activity reflecting cyclical BOLD patterns / low-frequency patterns of the BOLD response. I.e. rs-fMRI is the only fMRI that has ever made much sense a priori. The solution to this is maybe to combine EEG (extremely high temporal resolution, clear use in monitoring realtime brain changes like meditative states and in biofeedback training) with fMRI, as in e.g. [5]. But, it may still well be just the case fMRI remains mostly useless. [1] Elliott, M. L., Knodt, A. R., Ireland, D., Morris, M. L., Poulton, R., Ramrakha, S., Sison, M. L., Moffitt, T. E., Caspi, A., & Hariri, A. R. (2020). What Is the Test-Retest Reliability of Common Task-Functional MRI Measures? New Empirical Evidence and a Meta-Analysis. Psychological Science, 31(7), 792–806. https://doi.org/10.1177/0956797620916786 https://doi.org/10.1177/0956797620916786 [2] Herting, M. M., Gautam, P., Chen, Z., Mezher, A., & Vetter, N. C. (2018). Test-retest reliability of longitudinal task-based fMRI: Implications for developmental studies. Developmental Cognitive Neuroscience, 33, 17–26. https://doi.org/10.1016/j.dcn.2017.07.001 https://doi.org/10.1016/j.dcn.2017.07.001 [3] Termenon, M., Jaillard, A., Delon-Martin, C., & Achard, S. (2016). Reliability of graph analysis of resting state fMRI using test-retest dataset from the Human Connectome Project. NeuroImage, 142, 172–187. https://doi.org/10.1016/j.neuroimage.2016.05.062 https://doi.org/10.1016/j.neuroimage.2016.05.062 [4] Ekstrom, A. (2010). How and when the fMRI BOLD signal relates to underlying neural activity: The danger in dissociation. Brain Research Reviews, 62(2), 233–244. https://doi.org/10.1016/j.brainresrev.2009.12.004 https://doi.org/10.1016/j.brainresrev.2009.12.004, https://scholar.google.ca/scholar?cluster=6420450573860538418&hl=en&as_sdt=0,5&as_rr=1 https://scholar.google.ca/scholar?cluster=642045057386053841... [5] Ahmad, R. F., Malik, A. S., Kamel, N., Reza, F., & Abdullah, J. M. (2016). Simultaneous EEG-fMRI for working memory of the human brain. Australasian Physical & Engineering Sciences in Medicine, 39(2), 363–378. https://doi.org/10.1007/s13246-016-0438-x https://doi.org/10.1007/s13246-016-0438-x

zerof1l 11mo ago

I wonder how much variation there is between a person who does certain mental activity regularly vs a person who rarely does it. If they were to measure a person who performs mental arithmetic on a daily basis, I'd expect his brain activity and oxygen consumption to be lower than those of a person who never does it. How much difference would that make?

cj 11mo ago
I did a fMRI study as a volunteer in college. It involved going to the lab and practicing the thing (a puzzle / maze) I would be shown during the actual MRI. I think I went in to “practice” a couple times before showing up and doing it in the machine. IIRC the purpose of practicing was exactly that, to avoid me trying ti learn something during the scan (since that wasn’t the intention of the study). In other words, I think you can control for that variable. (Side note: I absolutely fell asleep during half the scan. Oops! I felt bad, but I guess that’s a risk when you recruit sleep deprived college kids!)
subroutine 11mo ago
I worked in an fMRI lab briefly as a grad student. I suspect you'd be correct but perhaps not exactly why you'd expect. Studies using fMRI measure a blood-oxygenation-level-dependent (BOLD) signal in the brain. This is thought to be an indirect measure of neural activity because a local increase in neural firing rate produces a local increase in the need for, and delivery of, oxygenated blood. The question then is, do you expect a person who is really good at mental arithmetic to have less neural firing on arithmetic tasks (e.g., what is 147 x 38) than the average joe. I would hypothesize yes overall to solve each question; however, I'd also hypothesize the momentary max intensity of the expert to peak higher. Think of a bodybuilder vs. a SWE bench-pressing 100 lbs for 50 reps. The bodybuilder has way more muscle to devote to a single rep, and will likely finish the set in 20 seconds, while the SWE is going to take like 30 minutes ;)

deleted 11mo ago

[deleted]

antipaul 11mo ago

Biotech industrial complex fMRI is a cool, expensive tech, like so many others in genetics and other diagnostics. These technologies create good jobs ("doing well by doing good"). But as other comments point out, and practitioners know, their usefulness for patients is more dubious.

yboris 11mo ago

In related news: ironically, Psychedelics disrupt normal link between brain’s neuronal activity and blood flow - thus casting some doubt on findings that under psychedelics more of the brain is connected (since fMRI showed elevated blood flow, suggesting higher brain activity). https://source.washu.edu/2025/12/psychedelics-disrupt-normal-link-between-brains-neuronal-activity-and-blood-flow/ https://source.washu.edu/2025/12/psychedelics-disrupt-normal...

HocusLocus 11mo ago
As a caveman pondering "Stoned Ape Theory" during the rise of MRI in the 80s, having done light reading of Huxley, McKenna et. al, the claim that vascular variations were so tied to thought patterns in a purely calm and cognitive activity was fascinating. To see the brain of someone as they went through a deck of cards and paused to look at each... astounding! But frustrating also. My first question always was, was the person's hands busy going through the deck and holding up the cards, focusing on them... or were they merely shown the cards sitting still? It seemed the popsci articles often glossed over that information, and any simple "control for coordinated body movement" played second fiddle to the novelty of it all. Then I worked in a club where I was often surrounded by tripping people. I'd fetch them glasses of water and they would always drink. Do you know you can smell them, they smell like fear? The experience has every sweat gland working overtime. When I learned that I greeted this "tripping people MRIs light up indicating enhanced brain connectivity" with a grain of salt. I would not be the least bit surprised if the sweat gland thing also has the brain's vascular system in overdrive.
- yboris 11mo ago
  My favorite explanation for why LSD and similar psychedelics generate the visual patterns they do: mathematics of wrapping polar coordinates of the retina to the rectangular coordinates of the visual processing system: https://www.quantamagazine.org/a-math-theory-for-why-people-hallucinate-20180730/ https://www.quantamagazine.org/a-math-theory-for-why-people-...

SubiculumCode 11mo ago

I'll get raked for this, but as someone in the field, I can say with high confidence that the majority of comments in this thread are not from imaging experts, and mostly (mis)informed by popular science articles. I do not have the time to properly respond to each issue I see. The literature is out there in any case.

DANmode 11mo ago
Seeing HN take on your speciality or topic can be brutal. Condolences.
- Loughla 11mo ago
  I hide any thread that deals with education, education funding, or teaching in general for that specific reason. It really saddens me to see that this place is full of so much misinformation and anecdotes made into data (and usually with much more self-confidence than other forums, which is interesting to me). It's why I generally only ask questions, or ask for clarification instead of directly challenging something I think might be wrong now in threads that aren't related to something I have deeeeep personal knowledge of. I know when I'm out of my area, and don't want to add to the ignorance.
  - NemoNobody 11mo ago
    Challenging something with a question about it, is not adding to ignorance - if a statement/study/fact/belief can't hold to up to questions, from actual opposing critics, what's the point of that position existing? Being all "PC" and "nice" about stuff that is what it is, or isn't -- THAT adds to ignorance.
    - Loughla 11mo ago
      I guess maybe I didn't phrase that correctly - I ask challenging questions, but don't state the things I "know" without clarification first. I meant that I don't just pop off with "yeah, but in reality it's x, y, z" because I know that I'm probably ignorant of facts. I'll ask about x, y, or z first.

riazrizvi 11mo ago

The researchers found that “40% of increased fMRI signal correspond to a decrease in neuronal activity”, so it’s even worse than the headline.

rcv 11mo ago

I remember reading a paper back in grad school where the researchers put a dead salmon in the magnet and got statistically significant brain activity readings using whatever the analysis method à la mode was. It felt like a great candidate for the Ig Nobel awards.

prefrontal 11mo ago
That was our paper! We showed that you can get false positives (significant brain activity in this case) if fMRI if you don't use the proper statistical corrections. We did win an Ig Nobel for that work in 2012 - it was a ton of fun.
- dang 11mo ago
  This is one for https://news.ycombinator.com/highlights https://news.ycombinator.com/highlights! (I mention this so more people can know the list exists, and hopefully email us more nominations when they see an unusually great and interesting comment.) p.s. more on the salmon paper in this thread: https://news.ycombinator.com/item?id=46291600 https://news.ycombinator.com/item?id=46291600 https://news.ycombinator.com/item?id=46288560 https://news.ycombinator.com/item?id=46288560 https://news.ycombinator.com/item?id=46288557 https://news.ycombinator.com/item?id=46288557
  - jldugger 11mo ago
    Interesting -- I just use https://news.ycombinator.com/best?h=168 https://news.ycombinator.com/best?h=168 for a weekly roundup, but that only tracks posts. Might need to supplement it with highlights or similar. Reviewing the HN docs, https://news.ycombinator.com/bestcomments?h=168 https://news.ycombinator.com/bestcomments?h=168 might also be a good summary link.

isacdaavid 11mo ago

If you actually read their paper, you will find that it's only the sign of the correlation that is being questioned. The field has generally been aware of this interpretational gap, and that's why two-sided hypothesis tests are important. Cellular neuroscience and electrophysiology are only starting to face the challenges that fMRI faced 2 decades ago. To me this is like shitting on cars in 1925 because they kill people every now and then. Cars didn't go away, and nor will fMRI, until someone finds a better way to measure living people's brains. TUM's press is being sloppy, from conflating fMRI with MRI to presuming this is revolutionary, and ignoring earlier empirical work against this narrative (Windkessel's, Logothetis beta/gamma coupling, etc.)

Trickery5837 11mo ago

let me write the correct title for you: "new evidence that fMRI data should be processed and interpreted only in the presence of an adult"

eykanal 11mo ago

Now seems like a good time to remind folks of the Stanford dead fish fMRI study: https://law.stanford.edu/2009/09/18/what-a-dead-salmon-reminds-us-about-fmri-analysis/ https://law.stanford.edu/2009/09/18/what-a-dead-salmon-remin... fMRI has always had folks highlighting how shaky the science is. It's not the strongest of experimental techniques.

levocardia 11mo ago
fMRI methods and statistics have advanced quite a lot since the dead fish days, that critique does not really hold up today.
- prefrontal 11mo ago
  While I would agree that the prevalence of the problem has been minimized in fMRI during the last 15 years, I disagree that our critique does not hold up. The root of our concern was that proper statistical correction(s) need to be completed in order for research results to be interpretable. I am totally biased, but I think that remains worthwhile.
zahlman 11mo ago
I immediately thought of it too. Didn't realize it was that long ago.
dang 11mo ago
Discussed here. others? Risk of false positives in fMRI of post-mortem Atlantic salmon (2010) [pdf] - https://news.ycombinator.com/item?id=15598429 https://news.ycombinator.com/item?id=15598429 - Nov 2017 (41 comments) Scanning dead salmon in fMRI machine (2009) - https://news.ycombinator.com/item?id=831454 https://news.ycombinator.com/item?id=831454 - Sept 2009 (1 comment)
cafebeen 11mo ago
This study was really highlighting a statistical issue which would occur with any imaging technique with noise (which is unavoidable). If you measure enough things, you'll inevitably find some false positives. The solution is to use procedures such as Bonferroni and FDR to correct for the multiple tests, now a standard part of such imaging experiments. It's a valid critique, but it's worth highlighting that it's not specific to fMRI or evidence of shaky science unless you skip those steps (other separate factors may indicate shakiness though).

Olshansky 11mo ago

I didn't get my name on this, but contributed to it as an undergrad: https://ieeexplore.ieee.org/abstract/document/6903679 https://ieeexplore.ieee.org/abstract/document/6903679 We sped up fMRI analysis using distributed computing (MapReduce) and GPUs back in 2014. Funny how nothing has changes.

j45 11mo ago

What's surprising is the desire to have a silver bullet, or not solution. What's still amazing is fMRI can provide more visual context of what's happening in the brain, in what region, and activities that can help that improve. There are other complementary technologies like QEEG and SPECT that can also shed a light as well. It does seem the case that fMRI cann be more of a snapshot photo, and technologies like SPECT can provide more of a regional time lapse of activity.

voxleone 11mo ago

It is the microbiome, stupid. [just kidding]

subroutine 11mo ago

I was a grad student at UCSD when Ed Vul published Voodoo Correlations in Social Neuroscience [1], which stoked a severe backlash from the fMRI syndicate resulting in a title change to Puzzlingly High Correlations in fMRI Studies of Emotion, Personality, and Social Cognition [2]. There is a lot of interesting commentary around this article (e.g., “Voodoo” Science in Neuroimaging: How a Controversy Transformed into a Crisis [3]). To me it was fascinating to watch Vul (an incredibly rare talent, perhaps a genius), take on an entire field during his 1st year as assistant professor. 1. http://prefrontal.org/blog/2009/01/voodoo-correlations-in-social-neuroscience/ http://prefrontal.org/blog/2009/01/voodoo-correlations-in-so... 2. https://journals.sagepub.com/doi/10.1111/j.1745-6924.2009.01125.x https://journals.sagepub.com/doi/10.1111/j.1745-6924.2009.01... 3. https://www.mdpi.com/2076-0760/12/1/15 https://www.mdpi.com/2076-0760/12/1/15

instagraham 11mo ago

I might be oversimplifying, but isn't a lot of our neurological understanding about ADHD based on "fMRI shows decreased activity in the frontal cortex"? Or for that matter, our neurological understanding of a lot of mental health conditions. I know the actual diagnosis is several times more layered than this attempt at an explanation, but I always felt that trying to explain the brain by peering at it from outwards is like trying to debug code by looking at a motherboard through a bad microscope.

supersour 11mo ago
Yes this is true, but we actually have a lot more data to back this on than exclusively fMRI analysis - for example the ADHD medication guanfacine works only because the alpha 2 receptors happen to be wired differently in the prefrontal cortex than it is in other areas of the brain (a2 is inhibitory for most brain regions, but in the PFC they're positioned to amplify connections between neurons) , so by stimulating alpha 2 we allow for a more “top down” control from the prefrontal cortex than we do without, which improves executive function. So that is one extremely robust way to understand neurological conditions like ADHD or Parkinson’s
- instagraham 11mo ago
  With such medications, besides behavioural changes, how are they able to measure outcomes without fMRIs? Like knowing whether neuron connections are amplified or not?
  - D-Machine 11mo ago
    They don't, this is speculative (i.e. a theory) and almost certainly untrue (or a gross over-simplification), much like the early and now disproven serotonin theories of depression.
D-Machine 11mo ago
I do not think there is much neurological understanding about ADHD at all from current fMRI research, there are far too many quality and reliability issues here, not just on the fMRI end or limited amount of data overall, but in the measurement and diagnosis of ADHD itself (i.e. ADHD subtypes, and of course ADHD is a complicated diagnosis with many components manifesting to different degrees in different individuals, which makes it very hard to cleanly link to messy fMRI signals). Or, as I have commented elsewhere here, the idea that statements like "fMRI shows decreased activity" are ever valid is just fundamentally suspect (lower BOLD response could mean less inhibition or less excitation, and this is a rather crucial difference that fMRI simply can't distinguish). EDIT: Or to be more precise: it may well be that fMRI research suggests less metabolic activity in certain regions, but this could mean the region is actually firing more than normal, less than normal, is more efficient than normal, etc., and interpreting anything about what is functioning differently in ADHD, given this uncertainty, is what is going to be suspect. Your analogy is largely correct IMO.

NedF 11mo ago

[dead]

quasarj 11mo ago

Uh-oh

stainablesteel 11mo ago

> Many fMRI studies on psychiatric or neurological diseases – from depression to Alzheimer’s – interpret changes in blood flow as a reliable signal of neuronal under- or over-activation. Given the limited validity of such measurements, this must now be reassessed idk about that, the brain is complicated, blood flow itself may as well be a factor to interpret

sharts 11mo ago

So all the studies citing fmri data are now wrong probably? yikes

physPop 11mo ago

Unfortunately, for experts in the field, this is a "we know" article that probably shouldn't have been published, and belongs more in a textbook...

D-Machine 11mo ago
Yes this is ancient news for experts, but, IMO, most fMRI research outside of methodological research is quite practically useless at the moment because of deep measurement issues like these. So if awareness of this increases the skepticism of papers claiming to have learned things about the brain/mind from fMRI, then I'd say it is a net plus.

bookofjoe 11mo ago

>BOLD signal changes can oppose oxygen metabolism across the human cortex (no paywall) https://www.nature.com/articles/s41593-025-02132-9 https://www.nature.com/articles/s41593-025-02132-9