Probability and inter-stimulus interval effects on the P300 from auditory stimuli.
The relationship between target stimulus probability and inter-stimulus interval (ISI) on the P300 (P3) component of the event-related potential was assessed in two experiments. An auditory discrimination paradigm was employed wherein subjects indicated with a finger tap response the occurrence of a randomly presented 2000 Hz target tone embedded in a series of 1000 Hz tones. Experiment 1 presented stimuli with target probabilities of 0.10, 0.30, and 0.50 at ISIs of 1.5 or 3.0 s and produced P3 amplitudes which decreased with increases in target probability and were smaller at the shorter compared to the longer ISI. Experiment 2 presented stimuli with target probabilities of either 0.20, 0.50, or 0.80 at ISIs of 4.0 and 10.0 s and produced P3 amplitudes which were unaffected by either variable. P3 latency demonstrated relatively few changes in either experiment. When taken together with previous findings, the results suggest that inter-stimulus interval affects P3 amplitude by determining the amount of processing resources available during ERP generation.
Polich
J
J
Department of Neuropharmacology, Research Institute of Scripps Clinic La Jolla, CA 92037.
D000161:Acoustic Stimulation; D000328:Adult; D004569:Electroencephalography; D005072:Evoked Potentials, Auditory / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D011336:Probability; D011930:Reaction Time