Check whether it already is such an array, whether it is a filename that can be loaded with freesurferformats::read.fs.volume
into such an array, etc.
extract.volume.3D(stats, silent = getOption("fsbrain.silent", default = FALSE))
the obtained 3D array
a 3D array, 4D array or a string that can be treated as a filename to a volume image containing such an array.
logical, whether to suppress file reading messages.