视觉注意系统通过动态调节机制实现对目标信息的增强与对干扰信息的抑制。事件相关电位(ERP)成分中的N2pc和Pd分别被认为反映了注意选择与注意抑制的神经过程。本文系统回顾了N2pc与Pd成分的时序特征、脑区分布、功能机制及其任务依赖性...视觉注意系统通过动态调节机制实现对目标信息的增强与对干扰信息的抑制。事件相关电位(ERP)成分中的N2pc和Pd分别被认为反映了注意选择与注意抑制的神经过程。本文系统回顾了N2pc与Pd成分的时序特征、脑区分布、功能机制及其任务依赖性,梳理了其在视觉搜索、显著性驱动和工作记忆抑制中的应用证据。进一步对两者在注意系统中的交互关系进行综合分析,提出了“双机制模型”,强调N2pc与Pd作为注意调控系统中相辅相成的成分,共同构建了目标选择与干扰抑制的神经基础。最后,文章讨论了当前研究中的理论争议、方法局限以及未来在多模态整合、个体差异研究和临床应用等方面的发展方向。本文旨在为理解视觉注意的神经机制提供系统性综述与理论整合框架。The visual attention system dynamically regulates the enhancement of task-relevant information and the suppression of distracting stimuli. Within the framework of event-related potentials (ERPs), the N2pc and Pd components have been identified as neural markers of attentional selection and attentional suppression, respectively. This review provides a comprehensive overview of the temporal characteristics, spatial distribution, functional mechanisms, and task dependency of N2pc and Pd. We summarize key findings from visual search paradigms, saliency-driven capture studies, and working memory-guided attention tasks. A dual-mechanism model is proposed to conceptualize how N2pc and Pd work in concert to support efficient attentional control, with N2pc reflecting target selection and Pd reflecting the active suppression of distractors. We also discuss current theoretical debates, methodological challenges, and future research directions, including multimodal integration, individual differences, and clinical applications. This review aims to advance the understanding of the neurocognitive basis of visual attention by integrating evidence from electrophysiological studies of selection and suppression.展开更多
A novel surface-type nonvolatile electric memory elements based on organic semiconductors CuPc and H2Pc are fabricated by vacuum deposition of the CuPc and H2Pc films on preliminary deposited metallic （Ag and Cu） el...A novel surface-type nonvolatile electric memory elements based on organic semiconductors CuPc and H2Pc are fabricated by vacuum deposition of the CuPc and H2Pc films on preliminary deposited metallic （Ag and Cu） electrodes. The gap between Ag and Cu electrodes is 3040μm. For the current-voltage （I-V） characteristics the memory effect, switching effect, and negative differential resistance regions are observed. The switching mechanism is attributed to the electric-field-induced charge transfer. As a result the device switches from a low to a high-conductivity state and then back to a low conductivity state if the opposite polarity voltage is applied. The ratio of resistance at the high resistance state to that at the low resistance state is equal to 120-150. Under the switching condition, the electric current increases -- 80-100 times. A comparison between the forward and reverse I-V characteristics shows the presence of rectifying behavior.展开更多
文摘视觉注意系统通过动态调节机制实现对目标信息的增强与对干扰信息的抑制。事件相关电位(ERP)成分中的N2pc和Pd分别被认为反映了注意选择与注意抑制的神经过程。本文系统回顾了N2pc与Pd成分的时序特征、脑区分布、功能机制及其任务依赖性,梳理了其在视觉搜索、显著性驱动和工作记忆抑制中的应用证据。进一步对两者在注意系统中的交互关系进行综合分析,提出了“双机制模型”,强调N2pc与Pd作为注意调控系统中相辅相成的成分,共同构建了目标选择与干扰抑制的神经基础。最后,文章讨论了当前研究中的理论争议、方法局限以及未来在多模态整合、个体差异研究和临床应用等方面的发展方向。本文旨在为理解视觉注意的神经机制提供系统性综述与理论整合框架。The visual attention system dynamically regulates the enhancement of task-relevant information and the suppression of distracting stimuli. Within the framework of event-related potentials (ERPs), the N2pc and Pd components have been identified as neural markers of attentional selection and attentional suppression, respectively. This review provides a comprehensive overview of the temporal characteristics, spatial distribution, functional mechanisms, and task dependency of N2pc and Pd. We summarize key findings from visual search paradigms, saliency-driven capture studies, and working memory-guided attention tasks. A dual-mechanism model is proposed to conceptualize how N2pc and Pd work in concert to support efficient attentional control, with N2pc reflecting target selection and Pd reflecting the active suppression of distractors. We also discuss current theoretical debates, methodological challenges, and future research directions, including multimodal integration, individual differences, and clinical applications. This review aims to advance the understanding of the neurocognitive basis of visual attention by integrating evidence from electrophysiological studies of selection and suppression.
基金supported by the GIK Institute of Engineering Science and Technology,Pakistan and Physical Technical Institute of Academy of Sciences of Tajikistan
文摘A novel surface-type nonvolatile electric memory elements based on organic semiconductors CuPc and H2Pc are fabricated by vacuum deposition of the CuPc and H2Pc films on preliminary deposited metallic （Ag and Cu） electrodes. The gap between Ag and Cu electrodes is 3040μm. For the current-voltage （I-V） characteristics the memory effect, switching effect, and negative differential resistance regions are observed. The switching mechanism is attributed to the electric-field-induced charge transfer. As a result the device switches from a low to a high-conductivity state and then back to a low conductivity state if the opposite polarity voltage is applied. The ratio of resistance at the high resistance state to that at the low resistance state is equal to 120-150. Under the switching condition, the electric current increases -- 80-100 times. A comparison between the forward and reverse I-V characteristics shows the presence of rectifying behavior.
