Foxe John J, McCourt Mark E, Javitt Daniel C
The Cognitive Neurophysiology Laboratory, Nathan S. Kline Institute for Psychiatric Research, Program in Cognitive Neuroscience and Schizophrenia, 140 Old Orangeburg Road, Orangeburg, NY 10962, USA.
Neuroimage. 2003 Jul;19(3):710-26. doi: 10.1016/s1053-8119(03)00057-0.
The "line-bisection" task has proven an especially useful clinical tool for assessment of spatial neglect syndrome in neurological patients. Here, we investigated the neural processes involved in performing this task by recording high-density event-related potentials from 128 scalp electrodes in normal observers. We characterized a robust net negative potential from 170-400 ms poststimulus presentation that correlates with line-bisection judgments. Topographic mapping shows three distinct phases to this negativity. The first phase (approximately 170-190 ms) has a scalp distribution exclusively over the right parieto-occipital and lateral occipital scalp, consistent with generators in the region of the right temporo-parietal junction and right lateral occipital cortices. The second phase (approximately 190-240 ms) sees the emergence of a second negative focus over the right central parietal scalp, consistent with subsequent involvement of right superior parietal cortices. In the third phase (approximately 240-400 ms), the topography becomes dominated by this right central parietal negativity. Inverse source modeling confirmed that right hemisphere lateral occipital, inferior parietal, and superior parietal regions were the likeliest generators of the bulk of the activity associated with this effect. The line stimuli were also presented at three contrast levels (3, 25, and 100%) in order to manipulate both the latency of stimulus processing and the relative contributions from magnocellular and parvocellular inputs. Through this manipulation, we show that the line-bisection effect systematically tracks/follows the latency of the N1 component, which is considered a temporal marker for object processing in the ventral visual stream. This pattern of effects suggests that this task invokes an allocentric (object-based) form of visuospatial attention. Further, at 3% contrast, the line-bisection effect was equivalent to the effects seen at higher contrast levels, suggesting that parvocellular inputs are not necessary for successful performance of this task.
“线段二等分”任务已被证明是评估神经科患者空间忽视综合征的一种特别有用的临床工具。在此，我们通过记录正常观察者128个头皮电极的高密度事件相关电位，研究了执行该任务所涉及的神经过程。我们确定了刺激呈现后170 - 400毫秒出现的一个强大的净负电位，它与线段二等分判断相关。地形图显示该负电位有三个不同阶段。第一阶段（约170 - 190毫秒）在头皮上的分布仅在右侧顶枕部和枕外侧头皮，与右侧颞顶叶交界处和右侧枕外侧皮质区域的发生器一致。第二阶段（约190 - 240毫秒）在右侧中央顶叶头皮出现第二个负焦点，与随后右侧顶上叶皮质的参与一致。在第三阶段（约240 - 400毫秒），地形图以右侧中央顶叶负电位为主。逆向源模型证实，右侧半球枕外侧、顶下和顶上区域最有可能是与该效应相关的大部分活动的发生器。线段刺激还以三种对比度水平（3%、25%和100%）呈现，以操纵刺激处理的潜伏期以及大细胞和小细胞输入的相对贡献。通过这种操纵，我们表明线段二等分效应系统地跟踪/跟随N1成分的潜伏期，N1成分被认为是腹侧视觉流中物体处理的时间标记。这种效应模式表明该任务调用了一种以空间为中心（基于物体）的视觉空间注意形式。此外，在3%对比度下，线段二等分效应与在较高对比度水平下看到的效应相当，这表明小细胞输入对于成功执行该任务不是必需的。
