P300 Elicited by Multi Target Stimuli and/or Multi Standard Stimuli

Abstract

As a part of the research about psychological mechanisms underlying P300, in this paper, we studied latencies and amplitudes for the P300s elicited by more than one target stimuli and/or more than one standard rtimuli. We administered to 10 healthy adults four blocks of oddball paradigm using verbal sounds i.e., 1) single-single condition constituted of single target stimulus and single standard stimulus (condition 1), 2) single-multi condition constituted of single target stimulus and five standard stimuli (condition 2), 3) multi-single condition constituted of five target stimuli and single standard stimulus (condition 3), 4) multi-multi condition constituted of five target stimuli and five standard stimuli (condition 4). The results were as follows; 1) P300 latency was shortest in condition 1, and delayed in condition 3, then in condition 2, and the last was condition 4. 2) P300 amplitude was largest in condition 1, and decreased in condition 3, and then in condition 2, and the last was condition 4. These results showed that weakness of the contrast between figure (target) and ground (standard) in working memory caused by multi target stimuli and/or multi standard stimuli influence the P300 latency and amplitude, i.e., latency is delayed and amplitude is decreased. And besides, in order to elicit P300, the ground made by single standard stimulus is thought to be more important rather than the figure made by single target stimulus to make up contrast between the figure and the ground in working memory.