fMRI analysis of visual responses using the "Second-Order Contrast" model (Kay, Winawer, et al.)
cell: A cell array of C categories, each containing a matrix of images shaped X pixels * Y pixels * F frames. The file "stimulus.mat" from the website has this form.
stack: A matrix X * Y * C * F. Can also have a fifth dimension B for bands. This structure most easily allows slicing and indexing, for visualizing images.
flat: A matrix (XY) * (CF) * B, where each image has been turned into a vector, and category boundaries have been removed, although band distinctions remain. The "model steps" mostly operate on flattened images.
pixel vector: A matrix (XY) * C * F, where each image has been turned into a vector, but category boundaries remain. The Kendrick-style model fitting code expects something like a pixel vector, but with the dimensions flipped to be C * (XY) * F.