Transcranial Doppler sonography was used to measure cerebral blood flow velocity (hemovelocity, CBFV) from the left and right middle cerebral arteries during the performance of a 30-min simulated air-traffic control task in which knowledge of results (KR) and signal salience were manipulated. Critical signals were situations in which the simulated aircraft were on a potential collision course. Findings show that overall signal detection and CBFV both declined over time. While performance was more stable over time in the KR condition, performance declined in the no-KR condition. In addition, the initial level and temporal decline in CBFV were both greater for the KR condition than the no-KR condition. Results are interpreted in terms of the motivational effects induced by feedback and a resource model of vigilance.
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