A Comparison of the P300 Associated With the Visual Discrimination of Geometric Pictures, English Letters, and Chinese Radicals

Abstract

The P300 in the oddball task has long been utilized to investigate the processing of a wide range of stimuli, including perceptual objects and linguistic items. The comparability of the features and thus the functions of the P300 across domains however needs a closer examination. In this study, 55 healthy participants (27 men and 28 women; mean age = 21.8±2.2 years) completed three separate tasks with an identical 3-stimulus (target, distractor, and standard) oddball paradigm, but different visual objects (geometric pictures, English letters, and Chinese radicals, respectively). Assessing the two subcomponents (P3b and P3a) of the P300 in terms of latency, amplitude, and topography, the analysis revealed that the ERPs associated with the visual discrimination of letters and radicals were different from those associated with pictures. Specifically, in the picture task, the target elicited the P3b with a centroparietal maximum, whereas the distractor elicited the P3a with a frontocentral maximum and an earlier peak, that is, the surprisal effect. Both the target and the distractor however generated the P3b in the letter and the radical tasks. Further, whereas the letter target, the radical target, and the radical distractor appeared similar in P3b latency and amplitude, the letter distractor showed an attenuated and delayed P3b, suggesting lesser interference. These P300 effects document the similarities and differences of processing English letters versus Chinese radicals, both different from processing geometric pictures, and help to promote more precise knowledge transfer and theory generalization across domains. The mechanisms underlying the visual discrimination of these different research objects are discussed in light of these comparisons.