Di Pellegrino G, De Renzi E
Neurological Department, University of Modena, Italy.
Neuropsychologia. 1995 Feb;33(2):153-70. doi: 10.1016/0028-3932(94)00111-2.
Under conditions of bilateral simultaneous presentation a right brain-damaged patient consistently extinguished visual stimuli presented for 200 msec to the left visual field. He was submitted to a series of experiments aimed at assessing the variables that influence this phenomenon. Extinction persisted unmodified when stimulus presentation was lengthened to 500 msec, when the size of the left stimulus was four-fold that of the right stimulus and for whatever position the stimuli occupied on the two halves of the display. Single stimuli were always perceived, but their localization was transposed rightward. The only condition in which extinction was partially reduced was when the instructions called for total disregard of the right stimulus. The patient also extinguished the leftmost of two stimuli presented in the left space, while he always perceived both stimuli when they were presented in the right space. However, if attention was covertly moved to a point in the right space and two stimuli were displayed to either side of it, left stimuli were neglected 70% of the time. Though a left stimulus was never perceived, it slowed the RT to the identification of a right stimulus. These data are interpreted in the frame of the directional bias theory, which attributes extinction to a shift of attention towards the side ipsilateral to the lesion, caused by the imbalance between the opponent turning processors, controlled by the right and left hemisphere. However, the striking difference in the rate of extinction when both stimuli were presented to the left or to the right field implies a stepwise decrement in the deployment of attention by the damaged processor, when it enters in the opposite space.
在双侧同时呈现刺激的条件下，一名右脑损伤患者持续忽略呈现于左视野200毫秒的视觉刺激。他接受了一系列实验，旨在评估影响这一现象的各种变量。当刺激呈现时间延长至500毫秒时，当左侧刺激的大小是右侧刺激的四倍时，以及当刺激在显示屏的两半部分占据任何位置时，忽略现象均持续且无变化。单个刺激总是能被感知到，但它们的定位向右偏移。唯一能使忽略现象部分减轻的条件是，指令要求完全无视右侧刺激。该患者还会忽略呈现于左侧空间的两个刺激中最左边的那个，而当两个刺激呈现于右侧空间时，他总能感知到两者。然而，如果注意力被隐蔽地转移到右侧空间的一个点上，并且在该点两侧显示两个刺激，那么左侧刺激有70%的时间会被忽略。尽管从未感知到左侧刺激，但它会减慢对右侧刺激进行识别的反应时间。这些数据是在方向偏向理论的框架内进行解释的，该理论将忽略归因于由左右半球控制的对抗性转向处理器之间的失衡，导致注意力向损伤同侧转移。然而，当两个刺激都呈现于左侧或右侧视野时，忽略发生率的显著差异意味着受损处理器在进入对侧空间时，注意力分配会逐步递减。
