Cingulate cortex activation and competing responses: the role of preparedness for competition.
Regional cerebral blood flow (rCBF) was studied in a task, where a preparatory stimulus (S1) cued for an imperative second stimulus (S2) which was associated with a response. Two preparatory stimuli cued unequivocally each for one response. In contrast, a third preparatory stimulus cued for two response alternatives which appeared for the same ratio (each in 50% of all trials) introducing response competition. In a first experimental condition, non-arbitrary, unambiguous stimuli were used as S1 to enable the subjects to prepare their responses. In a second and third scan, arbitrary preparatory stimuli were used during different stages of awareness for the S1-S2 association. Subjects performed this task "naive" without knowledge about the S1-S2 association and also in an experimental condition being aware of the S1-S2 association. Button presses after unambiguous, non-arbitrary preparatory stimuli activated the right middle frontal gyrus and inferior parietal lobe if S1 was associated with a definite response. When the subjects did not know the S1-S2 relation, left prefrontal cortex activation was associated with trials including definite responses. Performing the same S1-S2 response condition after subjects knew their relation right prefrontal and left parietal areas became additionally engaged. However, in the first experimental condition using unambiguous, non-arbitrary stimuli and in the third, "aware" experimental condition when S1 was coupled with two response alternatives, the anterior cingulate cortex was activated. As these experimental conditions have in common, that the preparatory stimulus shares information about the upcoming competing response alternatives they highlight the evaluative role of the anterior cingulate cortex for competing actions.
Suchan
B
B
Institute of Cognitive Neuroscience, Ruhr-University of Bochum, Germany. Boris.Suchan@rub.de
Melde
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C
Hömberg
V
V
Seitz
R J
RJ
D000328:Adult; D000704:Analysis of Variance; D001288:Attention / Q000502:physiology*; D001931:Brain Mapping; D003463:Cues; D005260:Female; D007839:Functional Laterality; D006179:Gyrus Cinguli / Q000502:physiology*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008297:Male; D010775:Photic Stimulation; D049268:Positron-Emission Tomography / Q000379:methods; D017397:Prefrontal Cortex / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology; D012039:Regional Blood Flow / Q000502:physiology; D013997:Time Factors