The Impact of Task Demands on Fixation-Related Brain Potentials during Guided Search

Recording synchronous data from EEG and eye-tracking provides a unique methodological approach for measuring the sensory and cognitive processes of overt visual search. Using this approach we obtained fixation related potentials (FRPs) during a guided visual search task specifically focusing on the lambda and P3 components. An outstanding question is whether the lambda and P3 FRP components are influenced by concurrent task demands. We addressed this question by obtaining simultaneous eye-movement and electroencephalographic (EEG) measures during a guided visual search task while parametrically modulating working memory load using an auditory N-back task. Participants performed the guided search task alone, while ignoring binaurally presented digits, or while using the auditory information in a 0, 1, or 2-back task. The results showed increased reaction time and decreased accuracy in both the visual search and N-back tasks as a function of auditory load. Moreover, high auditory task demands increased the P3 but not the lambda latency while the amplitude of both lambda and P3 was reduced during high auditory task demands. The results show that both early and late stages of visual processing indexed by FRPs are significantly affected by concurrent task demands imposed by auditory working memory.

同步采集脑电图（EEG）与眼动追踪数据，为测量外显视觉搜索的感知与认知过程提供了独特的研究方法。依托该方法，我们在一项聚焦于λ波与P3成分的引导式视觉搜索任务中，采集到了注视相关电位（Fixation Related Potentials，FRPs）。悬而未决的核心问题在于，λ波与P3这两种注视相关电位成分是否会受到并行任务需求的影响。为解答该问题，我们在开展引导式视觉搜索任务的同时，通过听觉N-back任务对工作记忆负荷进行参数化调节，同步采集眼动与脑电图（EEG）数据。被试需在三种实验条件下完成任务：仅执行引导式视觉搜索任务、忽略双耳呈现的数字，或是在0-back、1-back、2-back任务中利用听觉信息。结果显示，随着听觉任务负荷升高，视觉搜索与N-back任务的反应时均显著延长，准确率均明显下降。此外，高听觉任务负荷会延长P3成分的潜伏期，但对λ波的潜伏期无显著影响；而在高听觉任务需求情境下，λ波与P3的波幅均出现显著降低。本研究结果表明，由注视相关电位所表征的视觉加工早期与晚期阶段，均会受到听觉工作记忆所带来的并行任务需求的显著影响。