Fu Shimin, Caggiano Daniel M, Greenwood Pamela M, Parasuraman Raja
Cognitive Science Laboratory, The Catholic University of America, DC 20064, USA.
Brain Res Cogn Brain Res. 2005 May;23(2-3):341-53. doi: 10.1016/j.cogbrainres.2004.11.014.
The neural mechanisms supporting visuospatial orienting and focusing were investigated by recording event-related potentials (ERPs) in a cued, line-orientation discrimination task. Search arrays flashed randomly in the left or right visual field and were preceded by peripheral cues that varied in validity (valid or invalid, with 50% each) and size (large or small, with 50% each). Facilitation of response time was observed for valid trials, regardless of cue size. In contrast to previous cued search studies, however, small (i.e., more precise) cues were associated with delayed responses. Both the timing and the amplitudes of the early ERP components, P1 and N1, were modulated by attentional orienting, with valid trials eliciting a larger and later contralateral vP1 (ventral P1) and a smaller and later contralateral N1 compared to invalid trials. Attentional focusing modulated only the amplitudes of the P1 component, with precisely cued trials eliciting a larger dP1 (dorsal P1) than less precisely cued trials at both contralateral and ipsilateral sites. Thus, both attentional orienting and focusing modulate early stimulus processing stages that overlap in time, but with dissociable effects on the scalp distribution of these components, indicating possibly different underlying mechanisms. In addition, the results support the notion that voluntary and involuntary allocations of visuospatial attention are mediated by different underlying neural processes.
通过在一个线索化的线方向辨别任务中记录事件相关电位（ERP），研究了支持视觉空间定向和聚焦的神经机制。搜索阵列在左视野或右视野中随机闪现，并在之前呈现不同有效性（有效或无效，各占50%）和大小（大或小，各占50%）的外周线索。无论线索大小如何，有效试验中均观察到反应时间的缩短。然而，与之前的线索化搜索研究不同，小（即更精确）线索与反应延迟相关。早期ERP成分P1和N1的时间和幅度均受到注意定向的调制，与无效试验相比，有效试验诱发更大且更晚出现的对侧vP1（腹侧P1）和更小且更晚出现的对侧N1。注意聚焦仅调制P1成分的幅度，在对侧和同侧部位，精确线索试验诱发的dP1（背侧P1）均大于不太精确线索试验。因此，注意定向和聚焦均调制时间上重叠的早期刺激处理阶段，但对这些成分在头皮上的分布有可分离的影响，这可能表明存在不同的潜在机制。此外，结果支持视觉空间注意的自愿和非自愿分配由不同的潜在神经过程介导这一观点。
