Abstract: Decades of work on dual-task performance and selective attention has provided clear and robust evidence that dividing attention (DA) during encoding generally impairs subsequent memory performance. However, recent research reports that detection of infrequent targets in a DA condition while encoding a series of images into memory can enhance memory of images on subsequent memory test. This unusual phenomenon is described as the attentional boost effect (ABE). Previous research has explored the mechanism underling the ABE, and a lot of evidence showed that the ABE primarily enhanced perceptual encoding of the target-paired items, leading to a robust memory advantage for the target-paired items. However, some results argued against the perceptual encoding hypothesis of the ABE (Mulligan et al., 2014). Thus, the present experiment explores whether the memory benefit of the ABE is attributed to the perceptual encoding of the stimulus or to the later phase of elaboration and rehearsal. To investigate the neural activity of ABE, event-related brain potential (ERP) technique was adopted to record electroencephalographic (EEG) data of 24 participants who engaged in a second target-detection task while encoding a long sequence of words. A total of 600 words were presented during the encoding phase. Among these words, 200 words were presented with target indicators (target words), 200 words presented with distractor indicators (target words), and others were presented without any indicators (baseline words). Participants were told to read aloud each word while monitoring a target indicator, and withhold the response when they saw a distractor indicator, or did not see any indicators. Then a recognition task was given to test the participants’ memory of the words. Recording and analyzing the behavioral data and ERP data in the encoding and recognition test phase. Behavioral results showed that words presented in the target trials were more accurately recognized than those presented in the baseline (p<0.001), or distractor trials (p<0.001). There was no significant difference in the memory of words between the distractor and baseline conditions (p=0.12). The ERP results showed that, during the study phase, baseline trials induced a larger negative N1(130-180ms) amplitude, compared with target and distractor trials, and there was a significant difference between target and distractor trials in N2 (250-350ms), P300 (350-500ms), and later 700-1000ms time windows. During the test phase, the ERP old/new effects (FN400) induced by target words and baseline words were mainly manifested in the anterior half of the brain for the 300-500ms time windows. In addition, we also found the difference of ERP between target words and distractor words was embodied in that target words produced a more positive ERP waveform than distractor words and went on to 800ms. In conclusion, the difference of ERP between target words and distractor words is not only reflected in the ERP components related to perceptual processing, but also in the ERP components related to later conscious recollection. These data lead us to conclude that ABE could enhance the perceptual encoding of the stimulus, and the later phase of elaboration and rehearsal.

Key words: attentional boost effect, target detection, ERP

摘要： 近期发现，采用目标探测任务作为二级任务时，目标探测条件不仅不会削弱，甚至会提高记忆成绩，产生注意促进效应（ABE）。为进一步探究目标探测的作用机制，研究采用事件相关电位（ERP）技术，对比目标与分心条件在编码和提取过程中所诱发的ERP差异。结果表明，两类条件在再认过程中所诱发的ERP差异不仅表现在早期与知觉加工相关的ERP成份上，并且一直持续到了后期与细节提取相关的ERP成分上。由此推测，ABE不仅体现在编码早期的知觉加工阶段，更会延续到后期的复述与精加工。

关键词: 注意促进效应, 目标探测, 事件相关电位（ERP）