One each was seen with left only and no activity. Increased task difficulty elicited two to three times the number of pixels activated in 5 of 8 volunteers in the left frontal area. In two other individuals, the nimber of pixels activated were unchanged in the left frontal area and one was decreased with the more difficult task. This may reflect the small number of volunteers studied, or the complex nature of increasingly difficult cognitive tasks and brain activation. We have noted activation in the primary auditory cortex and in frontal areas in volunteers performing serial addition tasks when given verbal stimuli.
More pixel activation is seen with increasing task difficulty in some individuals.
The most difficult task demonstrated frontal activity to some degree in all volunteers. These results suggest that an increasingly difficult cognitive task may assist in demonstrating subtle activation in a more robust manner. Variability of activation is noted from one frontal lobe to the other in the more difficult task. This may reflect the small numbers of volunteers studied, or the complex nature of difficult cognitive tasks and brain activation. Comparison between individuals may be problematic because of variable response to task.