The Background State:A Protective Mechanism For Information In Visual Working Memory

Visual working memory plays an important role in human's cognition.For the mechanism of the visual working memory,it has been generally considered that all the visual working memory representations are not stored in a common state,but can be also maintained in a background state.Visual working memory representation can be transferred from the online state to the background state.However,it is not clear about the storage properties of the background state.In previous studies,the storage state of memory representation was changed by using the retro-cue paradigms,but such paradigms have inevitable flaws in exploring the background state's storage properties.The current study modified the sequential encoding version of the change detection paradigm to change the storage states of the memory representation.Besides,the contralateral delay activity(CDA),an index of event related potential(ERP),was used to identify whether the memory representations had been transferred into the background state.The study included two experiments.In Experiment 1,the participants needed to encode two memory arrays respectively,then they had to retrieve the two memory arrays according to the different detection tasks(the combined detection task,inverted order detection task).The results showed that there was no difference of the CDA amplitude between the first memory array and the second memory array,suggesting that the information in the first memory array was transferred from the online state to the background state.Under the combined detection task,the CDA amplitude of the second memory array was significantly higher than that of the first memory array,suggesting that both the information in the two memory arrays were stored in the online state.For the behavioral results,the first memory array in the inverted order detection task showed a loss of information.However,the detection order might have a bad effect on the comparison of accuracy.In Experiment 2,the combined detection task was replaced by the same order detection task to explore the effect of the detection order and further explore when the impairment occurred(during the switching or during the retention after switching).The ERP results showed that the participants stored the information of the first memory array in the online state first,and then transferred them into the background state in both the two detection tasks.Besides,the performance of the first memory array did not improve with the earlier probe.The memory storage was impaired during the states switching.It also provided evidence for that the detection order had little effect on the comparison.The study draws the two conclusions based on the two experiments.The process of change of memory representation state would impair the storage.Once the information had been stored in the background state,they would be robust with little memory loss during the retention.The background state plays a protective mechanism for information in visual working memory.