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SubiculumCode 6 days 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.

Aurornis 6 days ago | parent | next [-]

> I do not have the time to properly respond to each issue I see. The literature is out there in any case.

I think your expertise would be very welcome, but this comment is entirely unhelpful as-is. Saying there are bad comments in this thread and also that there is good literature out there without providing any specifics at all is just noise.

You don't have to respond to every comment you see to contribute to the discussion. At minimum, could you provide a hint for some literature you suggest reading?

D-Machine 6 days ago | parent | next [-]

I have also published and worked for some years in this field, if that helps.

The literature is huge, and my bias is that I believe most of the only really good fMRI research is methodological research (i.e. about what fMRI actually means, and how to reliably analyze it). Many of the links I've provided here speak to this.

I don't think there is much reliable fMRI research that tells us anything about people, emotions, or cognition, beyond confirming some likely localization of function to the sensory and motor cortices, and some stuff about the Default Mode Network(s) that is of unclear importance.

A lot of the more reliable stuff involves the Human Connectome Project (HCP) fMRI data, since this was done very carefully with a lot of participants, if you want a place to start for actual human-relevant findings. But the field is still really young.

ahtihn 6 days ago | parent | prev | next [-]

> Saying there are bad comments in this thread and also that there is good literature out there without providing any specifics at all is just noise.

Nah, it's not noise. It's a useful reminder not to take any comments too seriously and that this topic is far outside the average commenter's expertise.

throw10920 5 days ago | parent | next [-]

> Nah, it's not noise

Yes, it factually is, because...

> It's a useful reminder not to take any comments too seriously

...this is factually incorrect, because GP comment is literally not saying that - it's a specific dunk on a specific subset of critical comments with zero useful information about which comments or bad or why they're bad or any evidence to back up the assertion that they're bad or anything else useful.

(GP did go back and respond to some other comments with specific technical criticisms - after they made this initial comment. The initial comment itself is still highly problematic, as are fallacious praise of it, like this one.)

pessimizer 6 days ago | parent | prev [-]

It's definitely noise. Not recognizing it as noise is why phone and email scams work.

I say this as a psychologist who is advising you to ignore all claims to the contrary, because they are misinformed. It is clear from the literature.

mattkrause 6 days ago | parent | prev [-]

I'll co-sign SubiculumCode's comment -- there's a lot of yelling about how bad fMRI is generally, which is not particularly fair to the fMRI research (or at least the better parts of it) or related to the argument.

The BOLD signal, the thing measured by fMRI, is a proxy for actual brain activity. The logic is that neural firing requires a lot of energy and so active neurons will being using more oxygen for their metabolism, and this oxygen comes from the blood. Thus, if you measure local changes in the oxygenation of blood, you'll know something about how active nearby neurons are. However, it's an indirect and complicated relationship. The blood flow to an area can itself change, or cells could extract more or less oxygen from the blood--the system itself is usually not running at its limits.

Direct measurements from animals, where you can measure (and manipulate) brain activity while measuring BOLD, have shown how complicated this is. Nikos Logathetis and Ralph Freeman's groups, among many others did a lot of work on this, especially c. 2000-2010. If you're interested, you could check out this news and views on Logathetis's group's 2001 Nature paper [1]. One of the conclusions of their work is that BOLD is influenced by a lot of things but largely measure the inputs to an area and the synchrony within it, rather than just the average firing rate.

In this paper, the researchers adjust the MRI sequences to compare blood oxygenation, oxygen usage, and blood flow and find that these are not perfectly related. This is a nice demonstration, but not a totally unexpected finding either. The argument in the paper is also not "abandon fMRI" but rather that you need to measure and interpret these things carefully.

In short, the whole area of neurovascular coupling is hard--it includes complicated physics (to make measurements), tricky chemistry, and messy biology, all in a system full of complicated dynamics and feedback.

[1] https://www.nature.com/articles/35084300

DANmode 6 days ago | parent | prev | next [-]

Seeing HN take on your speciality or topic can be brutal.

Condolences.

Loughla 6 days ago | parent | next [-]

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.

DANmode 6 days ago | parent | next [-]

A great habit - especially when your question is an irresistible, easily-addressed homerun to a domain expert wandering through the thread looking for an entry-point.

NemoNobody 6 days ago | parent | prev [-]

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 6 days ago | parent [-]

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.

Der_Einzige 6 days ago | parent | prev [-]

https://en.wikipedia.org/wiki/Gell-Mann_amnesia_effect

Or worse, your whole field can be insitutionally blind to its own failings and randoms outside of it actually DO know more than you!. Chiropractors are literally worthless and being told "oh you don't get it bro" by them is their cope for being scammers, not an example of "their Gell Mann amnesia"

strongpigeon 6 days ago | parent | prev | next [-]

I’m sure you’re right, but given the spectrum of answers here, it’d be much more useful to point out which ones you think are wrong.

xandrius 6 days ago | parent | prev | next [-]

There are literally less than 20 top level comments and this one is (at least for me) the 2nd or 3rd.

Instead of a nothingburger, you could have used your academic prowess to break down the top 1/2 misconceptions with expertise.

You might not have time to respond to all the comments but a couple of clarifications could have helped anyone else who doesn't comment without experience.

Just saying that next time you can be the change you want to see in HN instead of wasting text telling us how ignorant we are.

nerdface 6 days ago | parent | prev | next [-]

I'm not a specialist by any means, although I am a patient of an fMRI. One thing I will note is that in the eventual, resultant paperwork from the broad array of tests I had, the fMRI was not noted whatsoever, neither was it discussed with me by any of the numerous neurologists or surgeons involved in my case. I was quite curious as to why it was performed at all, but presumably it was some formality to check a box.

D-Machine 6 days ago | parent [-]

It makes sense they wouldn't look at it, there are very few, if any, well-validated clinical uses for it. However, they might have taken it as a baseline for later comparison, and it is definitely plausible when surgery is involved that visible abnormalities could be seen in fMRI that might not show up in MRI, either now or later.

I don't think there would be much clear guidance for them on how to interpret any such fMRI abnormality on its own, but it might still be something useful for further investigations, and this might especially be the case for surgery. It might also have been done as part of research, if you consented to anything like that?

I am NOT an expert on fMRI in medical contexts, but you can surely get a rough idea of the potential value of fMRI with a quick search: https://scholar.google.ca/scholar?q=fMRI+surgery+brain&hl=en...

nerdface 4 days ago | parent [-]

I raise this as given the extent of research performed on my brain, the fMRI was not discussed with me whatsoever, nor was it mentioned in the pre-operative justifying factors. I raise this in relation to this submission; I hadn't given it any thought before.

Thanks for the link, useful to read.

Der_Einzige 6 days ago | parent | prev | next [-]

This is also true when HN talks about AI/ML :)

physPop 5 days ago | parent | prev [-]

agree. especially the comments saying "just address it". Its a lot of technically complicated interactions between the physics, imaging parameters, and processing techniques. Unfortunately the end users (typically neuroscience/psych grad students in labs with minimal oversight) usually run studies that just "throw everything at the wall and see what sticks" not realizing that is the antithesis of the scientific method. No one goes in to a resting state study saying "we're going to test if the resting state signal in the <region> is <changed somehow> becuase of <underlying physiology>". They instead measure a bunch of stuff find some regions that pass threshold in a group difference and publish it as "neural correlates of X". Its not science, and its why its not reproducible. People have build whole research programs on noise.

D-Machine 5 days ago | parent [-]

The meaningless NHST ritual is so harmful here. Imagine what we might know by now if all those pointless studies had used their resources to do proper science...