The Interaction Mechanism Between Perceptual Load Modulation And Working Memory Guidance

The human cognitive system has limited capacity and cannot process all information it receives. Selective attention plays a critical role in human information processing, preventing distractor interference by allocating limited resource to the task relevant stimuli. A large body of research has indicated that perceptual load and working memory guidance are two important factors which would determine the selective attention.The locus of selective attention is a central debate in cognitive psychology, mainly for the argument between the early-selection and the late-selection point. Early-selection accounts suggest that attentional selection occurs early, after the rudimentary analysis of physical features, and unattended stimuli are not fully perceived In contrast, late-selection accounts suggest that perception has unlimited capacity and all information get perceptual processing. To settle the dispute, researchers proposed the perceptual load theory of selective attention, which claim that the locus of selective attention depends on the level of perceptual load. Under low perceptual load, the process of relevant stimuli exhausts a few of attentional resource, and the surplus capacity of perception will "spill over" to perceive distractor, resulting in interference from task-irrelevant information. In contrast, high perceptual load for relevant stimuli exhausts the limited capacity of perception, therefore the distractor will not be perceived and the interference from distractors will be eliminated.In addition to perceptual load, working memory representation is another factor believed to influence attentional selection. According to the biased competition model of visual selection, the information processing capacity is limited and the neural representations of the different objects in the array are mutually inhibitory, competing for access to higher level processing. If the object was represented in working memory, such top-down control signals can bias selection in favor of the object whose features were same or similarity with working memory content. The attentional template held in working memory make those items matching the "template" capture attention automatically.In the field of selective attention, the perceptual load theory believes that the interference from task-irrelevant distractor is eliminated when attentional resources are fully consumed by task-relevant material. However, the biased competition model proposes that the attention can be guided to the object matching the WM content automatically. We can speculate that the interference from distractor will be observed consistently if the distractor matches an image in working memory even in high perceptual load condition. Interestingly, such prediction contradicts perceptual load theory. So what will happen when perceptual load and working memory guidance exert their effect on selective attention together? This study has two purposes:one is to explore whether the working memory guidance can occurred in early visual processing stage; another one is to discuss the time course and neurotic mechanism of the interaction between working memory guidance and perceptual load modulation.To study this issue, two groups of participants were recruited in this study, finishing Experiment1and Experiment2respectively. In the Experiment1, the experiment design adopted the attention capture paradigm. Participants were asked searched for two target letters (X and N) among6letters arranged in a circular array; meanwhile ignored the meaningless picture on the left or right. In the high perceptual load, the non-target letters were different. In the low load condition, the non-target letters were5Os. The irrelevant distractor condition was present (the search stimuli and distractor were all present) or absent (only the search stimuli was present). This experiment aimed at examining the effectiveness of perceptual load. The behavioral results showed that an entirely irrelevant distractor can interfere with target task performance at low perceptual load but not at high perceptual load. These result indicated that choose meaningless image as distractor also can replicated the classical findings of perceptual load and exclude the influence from material difference or culture difference.Based on the Experiment1, the Experiment2combined working memory task. The event-related potentials (ERPs) were adopted to explore the time course and neurotic mechanism of the interaction between working memory guidance and perceptual load modulation. Among the Experiment2, participants were asked to perform a delayed-match-to-sample task which to accomplish perceptual load task and hold a picture in memory at the same time. The experiment settings of perceptual load task were same to Experiment1, excepting the distractor always appears and either identical to the content of WM or different. The matching proportion was50%. In the experiment, the behavioral data and EEG data was simultaneously recorded. Behavioral results showed that memory guidance effect was not reliably eliminated by high perceptual load. ERP results further reveal the internal mechanism of interaction between perceptual load and working memory guidance. Firstly, the significant WM guidance effect was present on the P1component (90-130ms) under either low perceptual load or high perceptual load condition. This result suggested that working memory guidance occurred earlier than perceptual load modulation. Secondly, the memory guidance effect on N1component (160-200ms) was eliminated by high perceptual load and this effect was not influenced by low load. Standardized Low Resolution Electrical Tomography Analysis (sLORETA) showed that the WM guidance effect for P1was localized to the temporal-occipital cortex; while the perceptual load influenced WM guidance for N1was localized to the parietal area.The findings from this study suggest that when the perceptual load and working memory exert their effect on selective attention together, working memory effect occurred earlier than perceptual load. The stimuli that matching with working memory content capture attention automatically and was modulate by the level of perceptual load. Specifically, high perceptual load eliminate the working memory guidance effect. In conclusion, working memory guidance was present in early visual processing stage (temporal-occipital cortex) and modulates by the level of perceptual load.