Figure 2.

Hierarchically organized subtractions involving the same task conditions as shown in Fig. 1 with the difference being that these images represent areas of decreased activity in the task condition as compared with the control condition. Note that the major decreases occurred when subjects read the visually presented nouns aloud as compared with viewing them passively as they appeared on the television monitor (row 3); and when they said aloud an appropriate verb for each noun as it appeared on the television monitor as compared with reading the noun aloud (row 4). Combining the information available in Figs. 1 and 2 provides a fairly complete picture of the interactions between tasks and brain systems in hierarchically organized cognitive tasks when studied with functional brain imaging.