The Distractor Processing In Visual Working Memory:An ERPs And Eye-movements Study

Visual working memory can process and maintain only 3-4 objects simultaneously.This extremely limited capacity necessitates efficient mechanisms to select targets from the immediate environment to be processed in memory and to restrict distractors from consuming capacity.However,if the current task has low perceptual load and uses only a portion of cognitive resources,the spared resources will automatically spread to distractors.As a result,the distractor activation will cause interference with the target information processing,so distractor inhibition plays a key role in good performance.By now,researches on distractor in visual working memory have only refered to individual difference in distractor filtering efficiency and the relationship with visual working memory capacity.There has no research on distractor activation and inhibition processing in visual working memory found yet.In this study,the change-detection paradigm was used to explore the the distractor activation and inhibition processing in visual working memory.28 participants taked part in the event-related potential(ERP)experiment and 26 participants taked part in the eye movement(EM)experiment.ERP experiment was used to monitor the contralateral delay activity(CDA)during maintenance stage of visual working memory,and the relevance between distractor processing and encoding extent was tested based on the changes of CDA amplitude at different encoding times.So far,CDA has been the only neurophysiological measure which can track the number of objects processing and maintaining in visual working memory on-line.EM experiment was used to track the eye movements features during encoding stage and comparison stage of visual working memory,in order to investigate the cognitive resources competition between target and distractor in visual working memory,the dynamic change and position effect of distractor processing during the whole course.ERP results indicated that when memory array was presented for 100ms,the CDA amplitude in the distractors-present condition was significantly larger than that in the two targets alone condition,but not significantly different from that in the four targets alone condition.When memory array was presented for 500ms,the CDA amplitude of the distractors-present condition was significantly smaller than that of four targets alone but was not significantly different from that of two targets alone.The presenting time of memory array extended from 100ms to 500ms,the CDA amplitudes of both two targets alone and four targets alone rose,while the CDA amplitude of the distractors-present condition fell significantly.EM results revealed that during the encoding stage,the AOI entering sequence of distractor was significantly earlier than that of target,and the AOI fixation duration of target was significantly longer than that of distractor.During the comparison stage,the AOI entering sequence of distractor was significantly delayed,and the AOI fixation duration of distractor significantly decreased in I and II quadrants,while the AOI fixation duration of target significantly increased in I and IV quadrants.The AOI fixation durations of both target and distractor in four quadrants were I,II,IV,and III in descending order.These results suggest that distractor is activated during primary encoding and inhibited during adequate encoding.Distractor is activated earlier than target,but then inhibited,while more cognitive resources are distributed to target.The activation of both target and distractor is up and right dominant.After the representation inhibition of distractor and the representation activation of target being maintained in visual working memory,the inhibition of distractor is enhanced while the activation of target is enhanced in comparing the new perceptual input with the representations.The inhibition enhancement of distractor is up dominant,while the activation enhancement of target is right dominant.The activation and inhibition of distractor,as two opposite mechanisms of distractor processing,are consistent in processing intensity.With two intuitive indicators,event-related potential and eye movement,the study reflects the cognitive resources competition between target and distractor in visual working memory,reveals the relevance between distractor processing and encoding extent,and describes the dynamic change and position effect of distractor processing in visual working memory.The relevance between distractor processing and encoding extent can provide theoretical basis for cognition training of improving the distractor inhibition ability.The dynamic processing course and position effect of target and distractor have practical guiding significance for goods displays,advertisement design,UI design,and other problems like these.