Target-to-target interval, intensity, and P300 from an auditory single-stimulus task.

Target-to-target interval (TTI) is a primary determinant of P300 amplitude, such that longer TTIs yield larger components than shorter intervals. Systematic manipulations of TTI affect component amplitude, latency, and associated response time in a fashion that suggests that the template update hypothesis can account for these outcomes. The present study examines whether manipulations of TTI (from 1 to 16 s) and stimulus intensity (soft and loud tones) produce outcomes consistent with this hypothesis. A single-stimulus task was employed in which only target stimuli were presented. P300 amplitude increased, peak latency decreased, and response time increased as TTI became longer, with less effect for soft compared to loud stimulus conditions on P300 amplitude at Pz. TTI increases also augmented N100 amplitude, with consistently smaller amplitudes obtained for soft relative to loud stimuli. Overall, P300 measures are sensitive to both temporal and physical stimulus factors. Theoretical implications are discussed.