Weiskrantz L, Rao A, Hodinott-Hill I, Nobre A C, Cowey A
Department of Experimental Psychology, University of Oxford, South Parks Road, Oxford OX1 3UD, England.
Proc Natl Acad Sci U S A. 2003 Sep 2;100(18):10500-5. doi: 10.1073/pnas.1734039100. Epub 2003 Aug 19.
The study is of brain activity in a blindsight subject (D.B.), who reports conscious visual afterimages of stimuli of which he is unaware when they are presented. This contrast offered a unique opportunity to study event-related potential recordings of conscious versus unconscious visual phenomena generated by the very same stimulus in the identical locus of the visual field. The behavioral results confirmed the reliability of the difference in the subject's report for inducing stimuli versus their aftereffects. The rationale of the event-related potential analysis was to subtract "on" signals from "off" signals, the latter associated with the onset of conscious events and the former for events that remained unconscious. Because there are inherent differences in on and off potentials, the subtractive resultants for the blind hemifield were compared with the same subtractions for the good hemifield when the subject was aware both of the stimuli and their afterimages. A differential pattern in subtractive resultants emerged with a strong anterior left frontal focus for the blind field and a posterior focus for the intact field. The results are compared with other studies suggesting an anterior focus for conscious visual events.
这项研究针对的是一位患有盲视的受试者（D.B.）的大脑活动。该受试者报告称，对于呈现的刺激，他没有意识，但却能产生有意识的视觉后像。这种对比为研究在视野相同位置由同一刺激产生的有意识与无意识视觉现象的事件相关电位记录提供了独特的机会。行为结果证实了受试者对于诱发刺激与其后效应的报告差异的可靠性。事件相关电位分析的基本原理是从“关闭”信号中减去“开启”信号，后者与有意识事件的开始相关，而前者与仍处于无意识状态的事件相关。由于开启和关闭电位存在内在差异，当受试者对刺激及其后像都有意识时，将盲半视野的减法结果与正常半视野的相同减法结果进行比较。减法结果出现了一种差异模式，盲视野在前额左侧有一个强烈的焦点，而完整视野在后部有一个焦点。研究结果与其他表明有意识视觉事件在前部有焦点的研究进行了比较。
