Anticipation causes increased blood flow to the anterior cingulate cortex

Increased cerebral blood flow in the anterior cingulate cortex (ACC) has been noted in a range of cognitively demanding tasks studied with PET. A PET study of 10 normal males was carried out using the bolus H2(15)O intravenous injection technique to examine the effects of anticipation on blood flow to the ACC. In a series of conditions, subjects 1) passively viewed flashing plus signs, 2) noted the occurrence of abstract patterns, 3) named animal pictures, 4) or carried out a semantic judgement on animal pictures. Anticipatory scans were carried out after the subjects were presented with the instructions but before they began the cognitive task, as they were passively viewing plus signs. Significantly increased cerebral blood flow to the ACC was found in all three cognitive tasks when compared with baseline. More importantly, a similar increase was observed in each of the anticipatory states when compared with baseline. When the anticipation scan served as the subtracted baseline for the cognitive task, the increase in blood flow was not significant. This pattern of activity suggests that receiving instructions, preparation, and anticipation of the cognitive task, rather than task-related processing itself, may be responsible for the increased blood flow in the ACC noted in many PET studies of simple cognitive tasks.