I had a conversation with a PhD neuroscientist who was quite prominent and good in her field. She didn't have nice things to say about fMRI studies. Full Stop

I had a conversation with a PhD neuroscientist who was quite prominent and good in her field. She didn't have nice things to say about fMRI studies. Full Stop. That was ~10 years ago, so I'm sure techniques have improved, but she was arguing on the principle that the time scales on which it can measure just aren't conducive to measuring the actual activity that neurons produce.