¥ You do not model the baseline condition
¥ e.g., ÒrestÓ, visual fixation,
high-low tone discrimination, or some
other simple task
¥ FMRI can only measure changes
in MR signal levels between tasks
¥ So you need
some simple-ish task to serve as a reference
point
¥ The baseline model (e.g., a + b ×t ) takes care of the signal level to which the MR signal returns when the ÒactiveÓ tasks are turned
off
¥ Modeling
the reference task explicitly would be redundant
(or ÒcollinearÓ, to anticipate a forthcoming jargon word)