Fig. 1.

Schematic depicting events during Experiments 1 and 2. (A) During Experiment 1, the pretarget portion of the trial began with a variable RCI, over which only passive decay could occur, followed by a task cue (LETTER or NUMBER), and then a CSI during which active preparation could also occur. Then a number–letter target was presented until the subject made their response. (B) In Experiment 2, task events consisted of a task cue, a CSI, and a target. Task events were grouped into sets of an initial event (T-1), during which experimental variables were held constant, and a second event (T-2), during which the experimental factors were manipulated. For fMRI analysis, each set was coded as an epoch starting at the onset of the T-1 cue; these epochs could be readily compared because, across the T-2 experimental conditions, the epoch history was identical up to presentation of the T-2 cue.