无空间线索化下视觉注意空间等级的ERP研究

ERP Effects on the Spatial Scale of Visual Attention without Spatial Cue

采用事件相关电位(Event-Related Potential,ERP)技术考察了无空间线索化下视觉注意资源在不同空间等级的分布情况。通过"预警信号-目标探测"范式,目标刺激随机出现在直径视角为3.2°、6.4°以及9.6°的三个等级圆上。反应时显示:对目标刺激的探测速度随注意范围增大而下降。脑电显示:三种条件下目标刺激诱发的N1和P3分别产生了不同程度的分离,主要表现为两成分的波幅随注意范围增大而减小。这表明个体在无空间线索化下可能自动地选择对不同空间等级进行资源分配。

Researchers have investigated the resource allocation of the spatial scale of visual attention by using the classic ＇cue-target＇ paradigm that is adopted in order to enable subjects to identify a target. Behavioral results have showed that target detection in attended areas is facilitated by the cue to target location. ERP data have indicated that the early components of P1 and N1 are probably related to the processing of the spatial scale in visual attention. It should be noted that the effect on the spatial scale of visual attention without spatial cues remains unclear. Using the experimental paradigm of ＂without spatial cues＂, this study investigated electrophysiological correlates of the resource allocation within the different spatial scale of visual attention. Event-related brain potentials were recorded for the appearance of target stimuli with which participants were required to respond quickly to the incoming stimuli during three conditions （visual angles of diameter were 3.2°, 6.4°, and 9.6°） of spatial position in which the target stimuli appeared randomly. Additionally, the ＇warning＇ （without any hint on the spatial information） just reminded the participants that the target stimuli might appear after an interval with a randomly varying duration between 0.8 and 1.2 s. The behavioral data showed that the mean reaction times （RTs） of detecting the target stimuli for the three spatial positions were 3.2° （M=494ms, SD=64）, 6.4° （M=518ms, SD=72）, and 9.6° （M=552ms, SD=74）. The repeated measures analyses of variance （ANOVA） indicated that the mean RTs were shorter for 9.6° than for 3.2° （p〈0.0001） and 6.4° （p〈0.0001）, and the mean RTs of 6.4° were also shorter than the case of 3.2°, indicating that the RTs on detecting a stimulus in unfixed position decreased significantly with the increase of visual angle. ERP results indicated that the N1 amplitude was higher for 3.2° and 6.4° than for 9.6° between 160 and 200 ms after the onset of the target stimuli. However, the N1 component elicited by 3.2° and 6.4° was not significantly different. Subsequently, a more positive event-related potential deflection during 3.2° and 6.4° than during the 9.6° in the 350 - 400 ms time window. Moreover, 3.2° elicited a more positive event-related potential deflection （P3） than 6.4° during the same interval. It is obvious that the ERPs amplitude of N1 and P3 components evoked by target stimuli increased with the reduction of visual angle, which provides a similar model of the behavioral data （e.g., RTs）. The Nlcomponent is related to the discrimination of the target stimuli that appears at the attended area, and the amplitude P3 component is suggested to reflect mental resource allocation during the processing of stimulus （e.g., larger amplitude is related to greater allocation of resources）. Therefore, this study observed a clear ERPs effect under the condition of uncued spatial information of the target stimuli, most likely reflecting the allocation of attention on the spatial scale adopting a selective pattern automatically.