Recording policies in functional magnetic resonance imaging
If I recall correctly, in BOLD fMRI an echo-planar imaging (EPI) sequence is typically used. In one example:


  44 slices were acquired, every 3 seconds, 96 times in a row, leading
  to a total number of 4,224 images acquired in 4 minutes and 48
  seconds.


— https://www.imagilys.com/functional-MRI-fMRI/

You can read more about EPI here. I think you will find the zig-zag pattern in this link interesting. See also this link for a description of EPI.

fMRI is slow and has a low temporal resolution, because the hemodynamic repsonse of the blood is around 6 second long. This is perhaps a limiting factor for fMRI, which is why there is a limit to optimizing the sequences. However, one real impact of faster sequences is to capture head movement artifacts more accurately. Other sequences are used in anatomical MR imaging, such as FLAIR.