Comerchero M D, Polich J
Department of Psychology, University of California, San Diego, La Jolla 92037, USA.
Clin Neurophysiol. 1999 Jan;110(1):24-30. doi: 10.1016/s0168-5597(98)00033-1.
Target/standard discrimination difficulty was manipulated systematically to assess how this variable affects target and nontarget P300 scalp distributions for both auditory and visual stimuli.
A 3-stimulus paradigm (target, standard, nontarget) was employed in which subjects (n = 16) responded only to an infrequently occurring target stimulus. The perceptual discrimination difficulty between the target and more frequently occurring standard stimuli was varied as Easy or Difficult in different conditions, while holding the nontarget stimulus properties constant.
When target/standard discrimination was Easy, P300 amplitude was larger for the target than the nontarget across all electrode sites, and both demonstrated parietal maximums. In contrast, when target/standard discrimination was Difficult, target amplitude (P3b) was larger parietally and occurred later than nontarget components, whereas nontarget amplitude (P3a) was larger and earlier than the target P300 over the frontal electrode sites. Similar outcomes across task conditions were obtained for both auditory and visual stimuli.
The findings suggest that target/standard discrimination difficulty, rather than stimulus novelty, determines P3a generation for both auditory and visual stimulus modalities.
系统地操控目标/标准刺激的辨别难度，以评估该变量如何影响听觉和视觉刺激下目标与非目标的P300头皮分布。
采用三刺激范式（目标、标准、非目标），其中16名受试者仅对偶尔出现的目标刺激做出反应。在不同条件下，将目标刺激与更频繁出现的标准刺激之间的感知辨别难度设定为容易或困难，同时保持非目标刺激的属性不变。
当目标/标准辨别容易时，在所有电极部位，目标刺激的P300波幅均大于非目标刺激，且两者均在顶叶出现最大值。相反，当目标/标准辨别困难时，目标波幅（P3b）在顶叶更大且出现时间晚于非目标成分，而非目标波幅（P3a）在额电极部位大于目标P300且出现时间更早。听觉和视觉刺激在不同任务条件下均获得了相似的结果。
研究结果表明，目标/标准辨别难度而非刺激新颖性决定了听觉和视觉刺激模式下P3a的产生。
