视觉工作记忆内容对自上而下注意控制的影响:一项ERP研究

The Influence of Visual Working Memory Contents on Top-down Attentional Control: An ERP Study

采用视觉搜索范式,以二维抽象对称图形为材料,通过记录\16名被试在长短两种时间间隔(ISI)条件和有效、中性、无效三种视觉工作记忆内容条件下的行为反应和事件相关电位(ERPs),探讨视觉工作记忆内容对自上而下注意控制影响的认知过程和脑机制。结果发现:(1)无论ISI长或短,有效信息条件(记忆图形与目标所在的背景图形相同)的反应时均显著短于无效信息条件(记忆图形与目标所在的背景图形不同)。(2)有效信息条件下的额区P2波幅显著大于中性信息条件(记忆图形不出现在搜索序列中);枕区P1、N1波幅和潜伏期在视觉工作记忆内容条件下差异不显著;短ISI条件下,有效信息条件下的枕区P300波幅显著大于无效信息条件;长ISI条件下,有效信息条件的枕区P300波幅显著小于无效信息条件。表明当目标出现在与记忆内容相匹配的客体中时,激活了工作记忆中的客体表征,以自上而下的方式优先捕获注意;同时ISI变化对此过程起着调节作用。

The biased competition model for attentional selection proposed by Desimone and Duncan （1995） provided a framework for researchers to understand the interaction between top-down working memory factors and bottom-up sensory factors in attentional control. This model suggested that the stimulus representation stored in visual working memory would automatically capture attention in a visual search. However, other studies found that the content of visual working memory played no role in attentional capture. In order to explore the influence of visual working memory content on top-down attentional control, we employed a visual search paradigm with a secondary memory task and recorded ERP’s. Sixteen participants performed the task under long or short ISI conditions. The short ISI varied randomly from 400 to 600ms, while the long ISI varied randomly from 800 to 900ms. Each trial began with a black fixation cross displayed on a gray background for 500ms, followed by a memory item （abstract shape） for 1000 ms, and a blank interval （ISI）. After the interval, a search array of four abstract symmetrical shapes containing an arrow each was presented for 2000ms, and participants had to use a button box to indicate the direction of the only horizontal arrow presented in these shapes. This was followed by a 200ms interval. Finally, a probe stimulus was displayed for 1500ms, and participants had to indicate whether this item was the same as the initial abstract shape presented on its own at the beginning of the trial. The next trail commenced after a 500ms intertrial interval. The search arrays were divided into valid （the memory item appears in the search array and contains the horizontal arrow）, invalid （the memory item appears in the search array, but does not contain a horizontal arrow）, and neutral （the memory item is absent from the search array）. The behavioral data demonstrated that the RTs were significantly shorter in the valid condition than those in the invalid condition regardless of ISI duration. The ERP data showed that the amplitudes of frontal P2 in the valid condition were significantly larger than those in the neutral condition. The amplitudes and latencies of occipital N1 and P1 did not show any significant differences between all visual working memory content conditions （valid, invalid and neutral）. However, the main effect of ISI was reliable on the amplitudes of both P1 and N1. The amplitudes of P1 in the short ISI condition were larger than those in the long ISI condition, by the contrast, the amplitudes of N1 in the short ISI condition were smaller than those in the long ISI condition. That finding was considered to be related to the time course of visual working memory processing. Furthermore, the amplitudes of P300 in the valid condition were larger than those in the invalid condition when the ISI was short, and in contrast, the amplitudes of P300 in the valid condition were significantly smaller than those in the invalid condition when the ISI was long. The overall findings suggest that the influence of visual working memory content on top-down attentional control was affected by the time course of visual working memory processing. In the valid condition where search targets matched the content of working memory, an automatic selection advantage was observed for RTs and ERPs.