基于视觉搜索的外源易化和返回抑制脑机制研究

BRAIN MECHANISM FOR EXOGENOUS FACILITATION AND INHIBITION OF RETURN IN VISUAL SEARCH

采用事件相关电位技术研究了在视觉搜索过程中的外源易化和返回抑制(inhibition of return,IOR)的相互关系。当外源注意保持在序列搜索过的位置上时,有一个延时反应(即IOR),伴随其产生的相关脑电成分有:分布在后顶的潜伏期为200ms的正差异、分布在前额叶内侧靠左的潜伏期为240毫秒的负差异,以及分布在两侧颞顶联合区的潜伏期为280ms的负差异。而当外源注意保持在平行搜索的位置上时,则出现了明显的易化效应,伴随其产生的脑电成分仅为分布在枕顶区域的潜伏期为280ms的负差异。这些结果表明,外源易化和IOR涉及了不同的脑区和神经过程,从而支持两者在机制上是可分离性的观点。

Exogenous orienting plays an important role in orienting to visual space. In this study, the authors investigated the different effects of exogenous attention in parallel and serial visual search tasks by recording event-related brain potentials （ERPs） from subjects detecting probes following a search task. When exogenous attention remained at the serial search locations, a delayed response was observed （i.e., IOR） and three ERP components appeared： a Pd200 at the posterior parietal areas, an Nd240 at the left prefrontal areas, and an Nd280 at the bilateral temporoparietal areas. When exogenous attention remained at parallel search locations, a faster response was observed （exogenous facilitation）. At this time, one ERP component appeared： an Nd280 at the middle occipito-parietal areas. It is found that the exogenous facilitation-related neural process occurs at approximately 280 ms, and the neural processes which occur around 200 and 240 ms were inhibitory-specific events in the serial search task. These results suggest that the exogenous facilitation and IOR involve different brain areas and/or neural processes that may appear independently and are therefore most likely two dissociable processes.