The Effect Of Memory Quantity On Active Suppression Of Irrelevant Information During Working Memory Filtering

Visual working memory has a limited capacity so that individuals need to store task-relevant information selectively.A recent study found that this selective storage of relevant information is achieved by actively suppressing irrelevant items during encoding consolidation,and that the need to suppress irrelevant items is positively correlated with the number of irrelevant items and the individual’s visual working memory capacity.However,their study was performed under the condition that only fewer target items to be stored and individuals had more remaining memory resources.Inhibition of irrelevant items may be due to a surplus of individual memory resources,with irrelevant items entering working memory to interfere with relevant content.However,inhibition of irrelevant items may also be independent of individual memory resource surplus,and individuals may need to actively inhibit irrelevant items in a working memory filtering task whenever they are present.Thus,the true relationship between the need for distractor inhibition and the individual’s stored resources is not clear.In this study,we used an event-related potential（ERP）approach to investigate the effect of memory quantity on the inhibition of irrelevant information by modulating the number of memory items,and attempt to reveal the process of individual inhibition of irrelevant information.In Experiment 1,a systematic lateralization change detection task was applied and the distractor items were presented alongside the target.Observers had to memorize the target items while ignoring the distractor items.The number of distractors was kept constant while the number of targets varied between 1 and 4.The reaction times（RT）and correctness rates were significantly different for both target load 1 and target load 4.ERP results revealed that the lateral distractors elicited a significant PD component in target load 1 condition,but only a significant N2 pc component in target load 4 condition.The lateral target item elicited significant N2 pc followed by a sustained CDA,and the CDA amplitude was larger in the target load 4 condition than in target load 1 condition.In addition to this,Experiment 1 also found that the distractor items elicited a significant early PD component during in both conditions,with no significant difference in early PD waveform amplitude between the two conditions.The procedure was identical to Experiment 1 with the following exception.The number of targets（i.e.,load1 and load4）remained fixed throughout a block of trials.Behaviorally,Experiment 2 were consistent with those of Experiment 1.The ERP results showed that the early PD amplitude was larger in the target load1 condition than in the target load4 condition.Finally,in all 2 experiments we measured WM capacity（K）in a separate standard change detection task prior to performing the WM filtering task.We found that the PD amplitude in target load 1 condition correlated with overall WM capacity K.Based on the results of Experiment 1 and experiment 2,this thesis mainly draws the following conclusions: first,the inhibition of distracting items is related to the number of memories.When the number of memories does not exceed the individual’s memory resources,distracting items may enter visual working memory and interfere with memory items,so the individual needs to inhibit distracting items at this time.Second,the inhibition process of distracting items is divided into two levels of inhibition: early PD and PD.The early PD may reflect early sensory suppression regulated by anticipation,and early PD will be elicited when individuals need to inhibit distracting items.PD reflects attentional inhibition implemented by subjects.Finally,we found that the distractor-elicited PD were also correlated positively with K,that is,participants with higher WM capacity showed better inhibition ability.