alt Hacker News> 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?
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> 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.
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.
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.