ANTICIPATION CAUSES INCREASED BLOOD-FLOW TO THE ANTERIOR CINGULATE CORTEX

Increased cerebral blood flow in the anterior cingulate cortex (ACC) h as been noted in a range of cognitively demanding tasks studied with P ET. A PET study of 10 normal males was carried out using the bolus (H2 O)-O-15 intravenous injection technique to examine the effects of anti cipation on blood flow to the ACC. In a series of conditions, subjects 1) passively viewed flashing plus signs, 2) noted the occurrence of a bstract patterns, 3) named animal pictures, 4) or carried out a semant ic judgement on animal pictures. Anticipatory scans were carried out a fter 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 al l three cognitive tasks when compared with baseline. More importantly, a similar increase was observed in each of the anticipatory states wh en compared with baseline. When the anticipation scan served as the su btracted baseline for the cognitive task, the increase in blood flow w as not significant. This pattern of activity suggests that receiving i nstructions, preparation, and anticipation of the cognitive task, rath er than task-related processing itself, may be responsible for the inc reased blood flow in the ACC noted in many PET studies of simple cogni tive tasks. (C) 1996 Wiley-Liss, Inc.