Habituation of P300 to target stimuli

Two experiments examined the effects on N100, N200, and P300 of 1) repeated target presentation, 2) interblock intervals, 3) knowledge of session end, and 4) reversal of targets and nontargets. In the first experiment, subjects (N = 40) performed an oddball task across six test blocks (35 targets per block). Statistical analyses showed that repeated target presentation resulted in P300 amplitude decreases (habituation) and P300 latency increases within and across test blocks (11.3 microV to 5.4 microV, 330 msec to 348 msec), and also resulted in N200 amplitude increases within blocks and N200 latency increases within and across blocks. Interblock intervals resulted in partial recovery of these habituation effects. Knowledge of session end increased P300 amplitude, while reversal of targets and nontargets had no effect. The latencies of N200 and P300 were positively correlated (r .55), while the amplitudes were not. The second experiment demonstrated P300 habituation at multiple scalp sites (Fz, Cz, Pz). Two factors that may relate to habituation of the P300 are decreased arousal level and degree of involvement in the task.