How do I analyse a “sparse-sampling” dataset?
• Set the TR to be the actual time from the start of one volume to the start of the next, regardless of how long each one actually takes to acquire. • If this TR is longer than say 10s then you should probably turn off “FILM prewhitening” in the “Stats” section. • What you do next, to create the model, depends on the following. If you are always presenting the stimuli at the same point within the “effective” TR (which would normally be setup so that you are actually gathering data near the peak of the response) and your effective TR is long enough so that you don’t have different stimulus responses getting mixed up together, then you can use the simple modelling approach below. Otherwise you need the “full” modelling approach. SIMPLE MODELLING • In this approach you can simply assume that the response to each stimulus is sampled purely by the TR following that stimulus. You can therefore use the single-column custom timing EV design, with an EV for each event type, and a 0 for all TRs
