and updating processes (Polich and Herbst 2000). P3 also is thought to reflect cognitive closure, or the termination of a mental process (Desmedt 1980; Verleger 1988), which involves inhibition over widespread cortical areas (Desmedt 1980; Verleger 1988; Rockstroh et al. 1992; Birbaumer et al. 1990; Tomberg and Desmedt 1998). The amplitude of P3 reflects inhibition of responses to irrelevant stimuli that the subject must ignore in order to respond effectively to the relevant targets (Desmedt 1980; Birbaumer et al. 1990; Klimesch et al. 2000). The timing of P3 occurrence (latency) reflects mental processing speed (Polich and Herbst 2000); the earlier and larger the P3, the easier the processing.
