| Abstract: | Slow brain potentials were recorded during the foreperiod of a reaction time task, and the effects of instructions governing the trade-off between speed and accuracy were investigated. One brain potential, a slow negative shift preceding S2, was largely attenuated under accuracy instructions. It is suggested that this shift is dependent on a motor response and that its amplitude reflects the level of motor preparation. Two other brain potentials, a slow positive and a slow negative wave, seem to depend on the psychological properties of S1. Enhanced amplitudes were found, when S1 provides information, besides its warning function. |
