Figure 4

Schematic comparison of the stimulus paradigms and sequences used. A period of a minute of each functional sequence is shown. The acquisition of each functional volume (consisting of 20 slices) is illustrated by the small lines underneath the graphs. Cycles of auditory stimulation are denoted as gray shades while cycles without the application of auditory stimuli are shown in white. The red line represents the expected BOLD response to the stimuli. The expected response to the scanner noise is shown by the dotted lines. (A) Paradigm 1 involved ten-second cycles of stimulus and silence applied in random order. This paradigm was combined with sequence 1, which acquired all images of one volume in rapid succession at the end of each cycle, permitting the response evoked by the scanner noise to decay before the next image acquisition. This method of image acquisition is known as sparse temporal sampling [20]. (B) Paradigm 2 consisted of 30-second periods of stimulus and silence presented in alternating order. This paradigm was combined with sequence 2, which continuously generated scanner noise resulting in constant auditory stimulation even in periods in which no stimuli were presented.