

N=15 is a normal size on FMRI studies. It is about the smallest size you can have and still make your significance cut offs while still detecting decently small effects. The time and cost is so much higher than other studies. Some of the bigger FMRI studies start to reach 30-40 ppl. Getting into clinical trial sizes of subjects is unheard of.
The other thing with FMRI studies that most everyone doesn’t understand is that they aren’t actually looking at activity. They are looking at the BOLD response (blood oxygen level dependance) and that is then correlated to activity. Meaning You can only see blood oxygen uptake. You are not seeing neuron firing, just the metabolic side effect of oxygen use after increased neuron use. This is why you will never be able to see something like a “thought process”. You can only track structures/locations used.
At the same time we know that no two brains are wired the same even for the smallest of tasks, but they will “structure” their wiring the same. There have been literally hundreds of studies that indirectly see that. Soeach other. Plot out cultural differences versus individual differences would be basically two variance plots on top of eachother.
Those chambers are normally only done around 2 or 2.5 atmosphere, 3 tops. Not enough to kill anyone if it cracked. A small pop and rushing sound at most depending on the crack size.