Anticipatory Adjustments during a Warning Interval: Cortical Negativity and Perceptual Sensitivity

Cortical negative afterwaves were recorded while subjects performed a warned signal detection task. Warning intervals of 500, 1200 and 1900 msec, and immediate and delayed responses were employed as experimental conditions. Detection sensitivity was best at the 1200 msec warning interval, which coincided with maximum cortical negativity. The response requirement manipulation had no effect on detection performance or brain wave amplitude. The results are interpreted as indicating an arousal based allocation of processing resources, indexed by cortical negativity.