What are the effects of MRIs and other electromagnetic devices on the human brain? Naturally they could move metals to or through the brain cell's membrane. I can also see the experience of being in a strange position, meditating, and attempting to be as still as possible for an hour and a half, might cause some long term effect. Have the effects of MRIs and other electromagnetic devices been studied comparatively on human psychology or neurology? Could you also mention the mental health aspects?
Yes, the effects of electromagnetic fields on the brain have been studied extensively, especially with respect to cellphone, WiFi, and other small devices that emit such fields. The results are typically mixed, but the overall consensus is that "it depends" - on the strength of the field, the environment, length of exposure, etc - and most modern consumer devices operate at levels well below safety margins.
The effects of MRIs on cognitive function have been studied to some degree, starting in the 1990s, early in their history. The most prominent cognitive effects known include dizziness, vertigo, concentration, and awareness. Most of these effects are temporary (limited to the time spent inside the MRI machine), typically only found in high-intensity MRIs, and in most cases require movement (movement is theorized to induce a changing magnetic field).
The long-term effects of exposure to MRIs are not well known. However, as MRIs are in very common use, and are often a core part of studies on mental health and cognitive function, their safety is indirectly tested regularly. As such, there is not much impetus to conduct a controlled long-term study. Note also that MRI-related health risks tend to be more important for the operators who are chronically exposed, rather than for the patients who are only briefly exposed.
For your case, you should find out the MRI field strength used: "the majority of systems operate at 1.5T, commercial systems are available between 0.2T–7T.". Most of the known effects on cognitive function are found with MRIs above 3T, which are relatively uncommon. Even if you were inside a particularly powerful MRI machine, as long as you remained perfectly still, no significant magnetic field fluctuations should occur, and even if you did move, the effects are temporary.