Figure 2.

Hemodynamic response showing activity over time (3 s per sample) within functionally defined ROIs in experiment 2. (a) Activity in a subregion of the left parahippocampal cortex functionally defined from experiment 1 (see text). When the Odd/Even Digit task was used as the baseline for activity in a rapid event-related design, both Novel and Familiar Pictures were associated with increased activity. When Rest was used as a baseline for activity, Novel Pictures were not associated with detectable activity, and Familiar Pictures were associated with decreased activity. (b) Activity in a subregion (see text) of the left motor cortex where the button pushes in the Odd/Even Digit task would be expected to be associated with significant activity. Here, the activity associated with Novel and Familiar Pictures was greater when Rest was used as a baseline than when the Odd/Even Digit task was used as a baseline. Thus, the effect of activity during a baseline task can be to reduce, eliminate, or even reverse the sign of the activity during the conditions of interest.