The effects of covert attention and stimulus complexity on the P3 response during an auditory continuous performance task.

This study examined the effects of motor responding and stimulus complexity on the event-related potential (ERP) P3 amplitude and latency during an auditory continuous performance task (A-CPT). Subjects were presented with undegraded and degraded syllables during two experimental conditions. In the motor attention (MA) condition participants performed a button press to target syllables. In the covert attention (CA) condition, participants listened for target syllables without responding. The ERP P3 amplitude for targets during MA and CA showed the expected anterior-to-posterior scalp topography, with the greatest amplitude at Pz. Although amplitudes across all scalp sites were greater for MA than CA target P3 responses, both MA and CA targets had greater P3 amplitudes than the P3 for the nontarget syllables (NT). There was no effect of stimulus complexity (degraded vs. undegraded) on P3 amplitude. However, stimulus complexity did affect P3 latency. Degraded syllables elicited longer P3 latency than undegraded syllables for both the MA and CA conditions. The amplitude and topography findings show that when stimulus probability is controlled through the use of a CPT paradigm, a reliable P3 component is present even when the task does not require a motor response to target stimuli.